GRUB 2 A Guide for Users Updated: 9/11/09, 9/12/09, 9/20/09, 9/22/09, 9/23/09, 10/04/09, 10/6/09, 10/7/09, 10/9/09, 10/12/09 (Dual booting, drivemap in Reply #1), 12/4/09 (edited References)
Bugs and Questions: See REFERENCES at the end.
In Progress -- pending the completion of the GRUB 2 Manual:
http://grub.enbug.org/Manual.
GRUB 2 Practical Reminders (a cheat sheet for those who know what they are doing)
See end of SECTION 4 Special Topics.
Installing Kubuntu--GRUB 2 placementTelling the Live CD installer where to put GRUB 2
-> See the Appendix
New:
Booting Windows XP on a non-first hard driveSee Reply #1
NEW Notes about some of the
new GRUB 2 commands: See Reply #1
NEW comment (10-0-09)
update-grub vs grub-mkconfigIt appears that update-grub has been replaced by grub-mkconfig.
HOWEVER, it appears that update-grub works fine, at least in 9.10 Karmic.update-grub is usually easier to use.
(To Do: Track the status of this)
I have made the switch throughout the how-to (in the first post of this thread).
Note: update-grub
The command update-grub generates a new grub.cfg file and replaces the existing grub.cfg with the newly generated grub.cfg (by default).
But, as explained next, you must specify the output file when using grub-mkconfig:
Note that
sudo grub-mkconfig
prints its output to the screen (default = stdout).
To print to the grub.cfg, use
sudo grub-mkconfig -o /boot/grub/grub.cfg
or
sudo grub-mkconfig --output=/boot/grub/grub.cfg
- - - - - - - - - -
TABLE of CONTENTSSECTION 1
Introduction History: GRUB Legacy, GRUB 2
Differences between GRUB Legacy and GRUB 2
GRUB 2 commands
Notes about some of the new GRUB 2 commands: See Reply #1
SECTION 2Key Facts About the Boot menu, grub.cfg Quick version -- Overview -- Details
/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
Rules for editing grub.cfg, /etc/default/grub, and the script files in /etc/grub.d
GRUB 2 device numbering is different: Partitions start at 1
Details
SECTION 3 Fixing ThingsA checklist of things to try to fix a broken system A Troubleshooting Outline Ctrl+Alt+Del will reboot your PC
Super Grub Disk: Very Important
Key commands:
grub-mkconfig and
sudo grub-install Timeout & Default OS, changing
Kernel options, changing
To see or to hide the boot menu
Missing OS entry in the boot menu
Editing the boot menu during booting: "e" key
The GRUB prompt grub> -- What to do with it => Getting information and booting an OS
Re-installing GRUB 2 using Live CD: Key Rescue Method
Using a Live CD to edit files in your OS
SECTION 4Special Topics Installing GRUB 2 to your PC
grub-install The most useful command The various types of command modes.
"c," grub>, Konsole BASH, edit "e", emu
TAB Completion
How to get information about your drives and devices
At Konsole : sudo fdisk -lu
At the GRUB 2 prompt: grub> ls
Boot menu: Adding or removing an OS entry
Boot menu: Create a custom boot entry
Boot menu: Making your own custom grub.cfg
Boot menu: Changing resolution, text colors, setting background image
4 ways to boot an OS: configfile, symlinks, direct booting, chainloader
Boot menu: Background image editing tip for those with widescreen monitors
Dedicated GRUB 2 partition: How to build it
GRUB 2 Flashdrive: How to build it
Use of the term "root"
GRUB's Root Device, the Linux statement: root=UUID=,
--root-directory=DIR INSTALL_DEVICE
Dual booting: See Reply #1
Booting XP on a non-first hard drive (drivemap): See Reply #1
Cheat sheet:
GRUB 2 Practical RemindersAppendix: Techniques--- Installing Kubuntu--GRUB 2 placement
--- Working as root, editing a file
--- Permissions: read, write, execute; change the execute bit
--- Chroot -- how to
References and Tutorials
See also REPLY #1 below this post for more GRUB 2 topics:
Notes about some of the new GRUB 2 commandsIncluded: chainloader, ls, grub-emu, grub-mkconfig (many tips!), root, rootnoverify (is gone), grub-setup
grub-install: See SECTION 4 above.
drivemap: See Reply #17 below; See Reply #1
loopback: See Boot From ISO (below)
Dual booting: How to set it upInstalling two or more Linux operating systems
RECOMMENDED METHOD
PROBLEMS
Messing up the booting -- fixing GRUB without re-installing Kubuntu
Windows topics
Installing XP (or 7? or Vista?) & Kubuntu:
How to set up dual booting (recommended outline)
Re-installed XP and now can't boot Kubuntu
XP on a non-first hard drive: (hdx,y), x > 1
Booting XP on a non-first hard driveThe
drivemap command in GRUB 2
Boot From ISO -- use of GRUB 2 loopback
Boot your Kubuntu Live CD ISO from your flashdrive
GPT: GUID Partition Table... for Kubuntu 9.10 and GRUB 2
=> Overcoming the "
2 TB disk size limit"associated with the conventional MBR
=>
Testing GRUB 2 on your GPT-partitioned flash drive= = = = = = = = = = = = = = = = = = = =
SECTION 1Introduction History: GRUB Legacy, GRUB 2
Differences between GRUB Legacy and GRUB 2
GRUB 2 commands
Notes about some of the new GRUB 2 commands: See Reply #1
History: GRUB Legacy, GRUB 2"Briefly,
boot loader is the first software program that runs when a computer starts. It is responsible for loading and transferring control to the operating system kernel software (such as the Hurd or the Linux). The kernel, in turn, initializes the rest of the operating system (e.g. GNU)." (gnu.org)
The original GRUB (GRand Unified Bootloader) was developed by Erich Stefan Boleyn, from which came the GRUB most of us know, GRUB version 0.9x, and that is now referred to as GRUB Legacy (or even GRUB 1 by some writers). GRUB 2 replaces GRUB Legacy. (GRUB 2 is actually the end result of versions GRUB 1.xx; e.g., 1,96, 1.97, ...)
For the history of GRUB and some interesting links, see
http://www.gnu.org/software/grub/GRUB 2 is cleaner, more efficient, powerful, and more elegant, in many ways it is simpler to use than GRUB Legacy.
GRUB 2:
http://www.gnu.org/software/grub/grub-2.en.htmlIts mailing list for development,
GRUB-devel:
http://lists.gnu.org/mailman/listinfo/grub-develAnd the Wiki:
http://grub.enbug.org/GRUB 2 is the default bootloader in 9.10
https://lists.ubuntu.com/archives/ubuntu-devel-announce/2009-June/000573.htmlDifferences between GRUB Legacy and GRUB 2From the user's view, the biggest difference between the two versions of GRUB concerns the
boot menu configuration file.
GRUB 2: /boot/grub/grub.cfg
GRUB Legacy: /boot/grub/menu.lst
The configuration file is used to generate the boot menu you see at boot time.
In GRUB Legacy, you can edit menu.lst directly and in any way you wish.
In GRUB 2, you should not edit grub.cfg directly. Instead, you edit the file /etc/default/grub (which contains some default settings); this file feeds data to scripts in the folder /etc/grub.d. And you may edit the scripts (text files) in the folder /etc/grub.d; these scripts are used to generate the configuration file /boot/grub/grub.cfg. When you need a new grub.cfg, simply do sudo grub-mkconfig -o /boot/grub/grub.cfg.
It is conceptually simple in GRUB 2:
You can edit the file /etc/default/grub and you can edit the scripts in /etc/grub.d, then run the command sudo grub-mkconfig -o /boot/grub/grub.cfg, and the file grub.cfg is automatically generated.
The configuration file in GRUB 2 grub.cfg looks different than the GRUB Legacy menu.lst. For example, in GRUB legacy, you use
default 0
timeout 5
In GRUB 2, default and timeout are variables, and it is
set default=0
set timeout=5
A boot entry in GRUB Legacy menu.lst might look like this:
title Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic
root (hd1,2)
kernel /boot/vmlinuz-2.6.24-24-generic root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
In GRUB 2 grub.cfg, it would look like this:
### BEGIN /etc/grub.d/10_Linux ###
menuentry "Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic" {
set root=(hd1,2)
linux /boot/vmlinuz-2.6.24-24-generic root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
}
### END /etc/grub.d/10_Linux ###
Note how the title line is changed in GRUB 2: Use
menuentry instead, put the text in quotes, and start the boot entry with a left brace {, ending it with a right brace }. Instead of kernel, the word linux is used; initrd is the same. Instead of root=, in GRUB 2 it is set root= (in GRUB 2, root is a variable).
sudo grub does not get you a GRUB 2 shell at KonsoleIn GRUB Legacy, the user may open a GRUB shell by typing sudo grub, and then use it to install/re-install GRUB (root-setup-quit) to a Master Boot Record or to a partition boot sector. In GRUB 2, there is no such option. Instead, the key command is the Konsole (BASH) command
grub-install. At Konsole, as root, you will use sudo grub-install to install/re-install GRUB 2 to a Master Boot Record or to a partition boot sector.
Device names have changed. In GRUB Legacy, the numbering of both hard drives and partitions start at zero. (hd0,0) is the first hard drive (hd0), the first partition (partition zero).
In GRUB 2, the numbering of hard drives also starts at zero: hd0 is the first hard drive. But
partition numbering starts at 1: (hd0,1) is the first hard drive, the first partition (partition one).
In GRUB Legacy, we use the find command; e.g., grub>find /boot/grub/menu.lst.
In GRUB 2, the search command replaces the find command: grub>search /boot/grub/grub.cfg.
In GRUB Legacy, the geometry command (at the grub> prompt) is very useful for listing devices as GRUB sees them on your PC. It is not used in GRUB 2. Instead
the list command ls (at the grub> prompt)
replaces the geometry command.
GRUB Legacy uses stages: stage_1, stage_1.5, and stage_2. Those are replaced in GRUB 2 by
boot.img (a 512-byte file that corresponds to stage_1 and is installed to a MBR); there is no stage_1.5 in GRUB 2; and
core.img in GRUB 2 takes the place of stage_2 (or, perhaps, of both stage 1.5 and stage_2). Details: See Section 4 the subsection "grub-install: A key command."
GRUB 2 Commands -- compared to GRUB LegacyComparison chart:
http://grub.enbug.org/CommandListKey useful items to note:
GRUB Legacy <--> GRUB 2find is replaced with
searchgeometry is gone and replaced by
lskernel (in menu.lst) is replaced by
linux (and other terms for different OSs)
title (in menu.lst) is replaced by
menuentry (in grub.cfg)
root is still used but is now
a variablesetup is gone; the work is done by
grub-installmap is replaced by
drivemapdevice is replaced by
loopback (makes a drive out of a file)
set is a GRUB 2 term used to set a variable
Notes about some of the new GRUB 2 commands: See Reply #1
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SECTION 2 Key Facts About the Boot menu, grub.cfg Quick version -- Overview -- Details
/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
Rules for editing grub.cfg, /etc/default/grub, and the script files in /etc/grub.d
GRUB 2 device numbering is different: Partitions start at 1
Details
Quick version:
/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
Rules:
-- The file /boot/grub/grub/cfg generates the boot menu.
-- Do not directly edit /boot/grub/grub/cfg.
-- You may edit (as root) /etc/default/grub.
(timeout, default OS, kernel options, resolution of the boot menu)
-- You may edit (as root) the scripts in /etc/grub.d.
-- Together, /etc/default/grub and the scripts in /etc/grub.d generate /boot/grub/grub.cfg.
-- To create a script, start with a text file as root: kdesudo kate
-- To make
filename executable: sudo chmod 744 /etc/grub.d/
filename or, sudo chmod +x /etc/grub.d/
filename-- To remove execute permission from
filename: sudo chmod -x /etc/grub.d/
filename-- To open Konqueror (Dolphin) as root: kdesudo konqueror
--
Generate a new configuration file /boot/grub/grub.cfg after editing /etc/default/grub and after editing, creating, or deleting scripts in /etc/grub.d, as follows:
sudo grub-mkconfig -o /boot/grub/grub.cfgExamples of grub.cfghttp://svn.savannah.gnu.org/viewvc/trunk/grub2/docs/grub.cfg?root=grub&view=markupOr: /usr/share/doc/grub-pc/examples/grub.cfg.
Also:
http://grub.enbug.org/grub.cfgAlso: GRUB 2 Basics
http://ubuntuforums.org/showthread.php?t=1195275GRUB 2 device numbering is new: Partitions y start at 1In GRUB 2 (as in GRUB Legacy), hard drives start at zero: hd0 is the first hard drive. In GRUB 2 (unlike GRUB Legacy), partition numbering starts at 1: (hd0,1) is the first partition in the first hard drive; (hd0,2) is the second partition in the first hard drive; (hd1,2) is the second partition in the second hard drive.
Linux device notation is the same as in GRUB Legacysda is the first hard drive; sdb is the second hard drive; sdc is the third; etc.
sda1 is the first partition of the first hard drive; sda2 is the second partition of the first hard drive; etc.
DetailsThe configuration file is called /boot/grub/grub.cfg, and it generates the
boot menu you see on your screen when you boot your PC (and so, /boot/grub/grub.cfg can be called the boot menu configuration file). You are NOT supposed to edit it (it is read-only). It is generated from a folder of scripts called /etc/grub.d. Another key file is /etc/grub/default and it feeds default data to the scripts in /etc/grub.d. You may edit /etc/grub/default (as root). You may also edit the scripts in /etc/grub.d (as root). If you create a new file in /etc/grub.d, you must make it executable if you want the entry included in the configuration file grub.cfg. If you do not want a script to execute (and so remove that entry from grub.cfg), you must remove the execute bit (i.e., remove the execute permission).
>>> Key reminder:
Generate a
new grub.cfg after changing anything in /etc/default/grub or /etc/grub.d by:
grub-mkconfig -o /boot/grub/grub.cfgExperts: Editing grub.cfg
The file is read-only, so change permission to include Write:
sudo chmod +w /boot/grub/grub.cfg
Then do the edits as root and Save. When grub-mkconfig is run, the file returns to read-only (chmod 444 or 400), AND your edits may be overwritten (and therefore gone).
Optional: After editing, restore permissions to disallow writing:
sudo chmod -w /boot/grub/grub.cfg or
sudo chmod 444 /boot/grub/grub.cfg
The default settings file /etc/grub/defaultThis file feeds data to the scripts in /etc/grub.d. It contains the Default operating system, the Timeout, kernel options, resolution of the graphical boot menu, and other default settings. You may edit this file with root privileges.
The folder of scripts /etc/grub.dThese scripts generate /boot/grub/grub.cfg when the grub-mkconfig command is run (as root). The order of the entries in grub.cfg corresponds to the order of the files in /etc/grub.d, starting with 00_header, then 01_scriptname, etc., through all files starting with NN_ where NN is a 2-digit number and _ is the underscore (Shift+(minus sign)); then comes scripts whose names start with a letter (e.g., a_anotherscript).
You may edit the script files (as root) or create new ones. To create a new entry in grub.cfg, you simply create a new script file: a text file that you make executable (like a program). To remove an entry from grub.cfg, remove the execute permission from the corresponding script file in /etc/grub.d. (If the entry corresponds to a custom script you wrote, you may also delete that script file from /etc/grub.d).
See SECTION 4 Special Topics -- Create a custom boot entry.
Editing the script files in /etc/grub.d:
Do your work as root.
To make the file /etc/grub.d/
filename executable:
sudo chmod 744 /etc/grub.d/
filename To remove the execute bit from the file
filename: sudo chmod -x /etc/grub.d/
filename When done, run
sudo grub-mkconfig -o /boot/grub/grub.cfg
to generate a new boot menu configuration file /boot/grub/grub.cfg.
GUI: How to set permissions
Open Konqueror or Dolphin as root (e.g., kdesudo konqueror).
Open the file.
Right-click > Properties > Permissions, Advanced Permissions
Tip: To open a file in /etc/grub.d (as root)
The files in /etc/grub.d are scripts. So, as root, if you click on one, it will want to execute or run like a program. Instead, to open a script for editing/viewing, right-click on the script file, Open With Kate or Kwrite. That opens the file as a text file. Now you can read it or edit it.
Details:
GUI, working as root: Open Konqueror (Dolphin) as root and work from there:
kdesudo konqueror
CLI, working as root: kdesudo kate /etc/grub.d/
script_nameQuick referenceThe (standard) files in /etc/grub.d (each is a script) are:
00_header
05_debian_theme: Set background, text colors, themes
10_hurd Locates Hurd kernels
10_linux Locates Linux kernels based on results of the lsb_release command.
The target are kernels located on the same partition as the root partition
of the current OS you are in (where this grub.cfg is located).
In contrast to: 30_os-prober (see below)
20_memtest86+: If the file /boot/memtest86+.bin exists, it is included in the boot menu.
30_os-prober: Searches for Linux and
other OS's on
all partitions; includes them in the boot menu.
40_custom: A template for adding custom boot menu entries.
See Appendix: permissions, working as root, making a file executable, Konsole, and other topics.
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SECTION 3 Fixing ThingsA checklist of things to try to fix a broken system A Troubleshooting Outline Ctrl+Alt+Del will reboot your PC
Super Grub Disk: Very Important
Key commands:
grub-mkconfig and
sudo grub-install Timeout & Default OS, changing
Kernel options, changing
To see or to hide the boot menu
Missing OS entry in the boot menu
Editing the boot menu during booting: "e" key
The GRUB prompt grub> -- What to do with it => Getting information and booting an OS
Re-installing GRUB 2 using Live CD: A Key rescure method
Using a Live CD to edit files in your OS
Troubleshooting OutlineWhen you can't boot into your OS, there are two possible causes:
the boot menu is flawed, and/or
the GRUB 2 installation is flawed.
To fix it, you have two choices:
boot into the OS somehow and fix it;
or
fix it from outside the OS (e.g., live CD, another OS, or live flash drive).
Before looking at these two choices,
note two important things:
> To fix the boot menu means to fix its configuration file /boot/grub/grub.cfg. You can sometimes do that temporarily using the edit-on-the-fly "e" key (see subsection below). To fix it permanently, you do NOT edit grub.cfg directly; but rather you edit the file /etc/default/grub and/or you edit the script(s) in /etc/grub.d, and then you use the command grub-mkconfig to generate a new grub.cfg.
> To fix the GRUB 2 installation, that usually means re-installing GRUB 2 using, at Konsole, the command grub-install. You can do this from inside the OS (if you can boot into it somehow), or from a Live Kubuntu CD or from another Linux OS on your hard drive. You cannot do it from the GRUB 2 prompt (grub>) when booting the PC. (In GRUB Legacy, you could do it by getting the grub> prompt and using the root and setup commands.)
Now let's look at each of your two choices for fixing the problem.
-->
How to boot into your OS when you can't seem to boot into your OS:
(1) SGD, or (2) use the grub>, or (3) use the "e" key.
Some tips and details:
> Use Super Grub Disk to boot into it. You may have SGD fix the boot (under GNU/Linux options), or simply use SGD to boot the OS so you can get into it. If you use SGD to fix the boot, it will re-install GRUB to your drive, so make sure that's what you want; also, it may do so using either GRUB Legacy or GRUB 2, depending on the SGD CD version you are using. Of course, if you can get booted into the OS, then you can fix anything and everything, so maybe you won't be feeling too picky at this point.
Note: Along these lines, you can also use your own GRUB 2 disk/flashdrive to boot your OS, if you built one.
> Boot into your OS yourself, manually, using the GRUB 2 prompt, grub>, ASSUMING you can get the prompt! (Sometimes, you can't.) See the Subsection below titled "The GRUB prompt grub> -- What to do with it."
> Boot into your OS yourself by fixing the boot menu (editing it "on-the-fly" using the "e" key when you see it on the screen). But sometimes, you don't see the boot menu. See the Subsection below titled "Editing the boot menu during booting: 'e' key" If you are successful, since these "e" edits are only temporary, after booting into the OS, you must make the changes permanent (by editing /etc/default/grub or the script(s) in /etc/grub.d and then generate a new grub.cfg using grub-mkconfig -o /boot/grub/grub.cfg.
-->
How to fix the problem from outside the OS:
(1) Use a Live CD, or (2) Fix it from another OS.
Some details:
> Use a Live CD.
From a Live Kubuntu CD (or most any live Linux CD), you can re-install GRUB and/or perform edits on files (/etc/default/grub or the script(s) in /etc/grub.d). See the subsections below: "Re-installing GRUB 2 using Live CD: Key Rescue Method" and "Using a Live CD to edit files in your OS."
> Fix the problem from another Linux OS, ASSUMING you are able to boot into one!
From there, you can edit files in your broken OS and/or re-install GRUB 2 using grub-install.
(NOTE: From the second OS, or even from a Live CD, you'd have to mount the broken OS partition; or perhaps looking in your file manager you'd see it is automatically mounted for you.)
[End of Troubleshooting Outline]
Ctrl+Alt+Del will reboot your PCIf your PC freezes up during the experiments/testing/troubleshooting of your bootloader, use
Ctrl+Alt+Del to re-boot the PC.
Be prepared to do something, though!
Examples of what to do:
-- Before using Ctrl+Alt+Del, put the Super Grub Disk CD in the CD tray so you can re-boot to it and rescue your OS.
-- Be prepared to press the key required to enter your BIOS setup. That will buy you some time, or give you a chance to change hard drive booting order, or put a live CD or SGD in the CD tray, or get your notes ready, etc.
-- If you have been getting a boot menu, let the PC reboot into it, then enter Edit mode (pressing the "e" key) or enter the GRUB 2 CLI (pressing the key "c"), then try to fix things from there.
Super Grub Disk: Very ImportantWhether you think you need it or not, get it now, free, as a bootable CD which will get you booted into your operating system in case you can't. SGD can be downloaded here:
http://www.supergrubdisk.org/ . Look for a CD ROM iso version, download it, burn it as an iso image to a CD (using K3b), test it briefly (by running it and stepping through a few menus but not choosing anything; then Quit; or, use it to boot into your OS).
Tip (using SGD to boot into your broken OS)
Choose GNU/Linux > Fix Boot, then select the broken partition.
Should you decide to simply Quit the SGD (without doing anything), do so, select reboot, enter your BIOS setup, remove the SGD CD, exit BIOS, and continue rebooting.
Key commands:
sudo grub-mkconfig and
sudo grub-installUse these two commands to "freshen up" your GRUB 2 installation.
grub-mkconfig: builds a new boot menu configuration file boot/grub/grub.cfg.
grub-install: builds a complete, fresh GRUB 2 installation, including /boot/grub/grub.cfg.
grub-mkconfigwill generate a new boot menu /boot/grub/grub.cfg. To do so, it uses /etc/default/grub and the scripts in /etc/grub.d. You should run this command after editing the default file or the scripts:
sudo grub-mkconfig -o /boot/grub/grub.cfg
or
sudo grub-mkconfig --output= /boot/grub/grub.cfg
See Reply #1 (to this post): Notes about some of the new GRUB 2 commands
sudo grub-install [INSTALL_ DEVICE]
installs or re-installs GRUB 2 to INSTALL_DEVICE.
See SECTION 4: grub-install: A key command
For now, here's some highlights.
sudo grub-install /dev/sda
installs GRUB 2
to the Master Boot Record of drive sda. And
sudo grub-install /dev/sda1
installs GRUB 2
to the boot sector of the partition sda1.
In doing so, grub-install
does a complete job of setting up everything.
Here's what it does: It builds the directory /boot/grub (if it doesn't already exit), copies GRUB 2 files to it from the "master" image directory /usr/lib/grub/i386-pc, probes your drives and devices and partition table, makes a new device.map, builds and installs boot.img (to MBR) and core.img, and builds /boot/grub/grub.cfg.
> Man page: (8)GRUB-INSTALL - Install GRUB on your drive.
http://grub.enbug.org/FranklinPiat/grub-install.manpageTroubleshooting-- After running grub-mkconfig, make sure that the line set default=(hdx,y) is correct (i.e., that the order of the menuentries did not change the default OS position).
--
sudo grub-install --recheck [INSTALL_DEVICE]
=> If you get an error running sudo grub-install, try it again with sudo grub-install --recheck [INSTALL_DEVICE].
Timeout and Default OS, changingThe
timeout is the length of time in seconds before the (highlighted)
default OS is automatically booted (if you do not intervene by touching a key). To change these values, open the file /etc/default/grub as root, make the changes, Save, exit, then generate a new /boot/grub/grub.cfg by running sudo grub-mkconfig -o /boot/grub/grub.cfg.
Opening /etc/default/grub as rootIf your file manager supports it, open the file manager, navigate to /etc/default/grub, right-click on the file, Actions, Edit as Root. Otherwise:
Open the file manager as root and work from there:
kdesudo konqueror
kdesudo dolphin
Or, open the file as root using Kate or Kwrite:
kdesudo kate /etc/default/grub
Example
GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DEFAULT=0 selects boot entry #0 (i.e., the first entry) as the default OS to be booted automatically. Boot entries can be seen in your /boot/grub/grub.cfg file; they start with a line
menuentry "some descriptive text" {
and end with
}
Boot entries are counted from zero; so the first menuentry is boot entry #0, the second menuentry is boot entry #1, etc.
Troubleshooting Tip:
Check default OS setting after grub-mkconfigIf you recently added/removed a boot entry (by editing a /etc/grub.d script) and ran grub-mkconfig to generate a new boot menu, you might have to check and edit the line "GRUB_DEFAULT= " (in /etc/default/grub) if the default sequence number changed.
(TO DO: Check also: sudo grub-set-default N.)
Kernel options, changingTo change these values, open the file /etc/default/grub as root, make the changes, Save, exit. (See Timeout and Default OS above for editing tips.) The line in /etc/default/grub looks like this (or similar):
GRUB_CMDLINE_LINUX="quiet splash"
To see or to hide the boot menuLook for this line in the file /etc/default/grub:
# GRUB_HIDDEN_TIMEOUT=0
With the # sign present, you will see the boot menu upon booting your PC.
With the # removed, you will not see the boot menu.
For a detailed explanation of the other ways this works, see
GRUB 2 Basics drs305
http://ubuntuforums.org/showthread.php?t=1195275Missing OS entry in the boot menuIf you run grub-mkconfig, and there is a missing entry in your boot menu, you can add that entry as a custom entry. See SECTION 4 below, Special Topics Boot menu: Create a custom boot entry.
Editing the boot menu during booting using the "e" keyWhen you boot/re-boot your PC, the boot menu appears. If you select an entry (an OS to boot into) and get an error, and if you are able to return to the boot menu (or re-boot again to get it), you may be able to fix things or to experiment with your boot menu to see if something will work. See the help tips at the bottom of the boot menu. At the boot menu, highlight an entry, press the "e" key, and you'll see the menuentry statements for that OS. See the help tips at the bottom of that menu. If you highlight a line, press the "e" key, that line will be displayed so you can edit it (using arrow keys, delete, etc.). Pressing ESC returns you to the previous screen.
The edits you make to the boot menu are
"on-the-fly" edits and are not permanent. To make them permanent, you'll have to edit /etc/default/grub and/or the script files in /etc/grub.d, perhaps even making a custom boot entry if necessary (SECTION 4 Special Topics Boot menu: Create a custom boot entry), then generate a new /boot/grub/grub.cfg file using grub-mkconfig.
The GRUB prompt grub> -- What to do with it => Getting information and booting an OS
You may get the GRUB prompt grub> in three ways:
> "c" key: You re-boot and upon seeing the boot menu, press the "c" key to get the grub>. (Or Control+c at the Edit mode menu.) (By pressing the ESC key, you get back to the boot menu.)
Or:
> No boot menu! Perhaps, you re-booted your PC and didn't see any boot menu but instead got dropped to the GRUB 2 prompt: grub>.
Or:
> You get a grub> when re-booting using your own GRUB 2 flash drive (which is what is usually supposed to happen!).
From the grub> prompt, you may be able to issue commands to
help you gather information about your drives
or
boot your computer.
Use these resources:
SECTION 4 Special Topics, the subsection
"4 ways to boot an OS" -- direct booting configfile, symlinks, chainloader
SECTION 4 Special Topics, the subsection
"How to get information about your drives and devices"
=> In particular, take special note of
the ls command and the use of TAB completion.
Example Booting using symlinks; and using the ls command
grub>
Use the ls command to see how GRUB 2 sees your drives and partitions:
grub>ls
From the output, you may decide to use ls again, this time listing files in certain directories.
For example, to investigate (hd0,8), you can
list the files under the root directory of (hd0,8), like this:
grub>set root=(hd0,8)
grub>ls /
And then to see the kernel(s) under /boot,
grub>ls /boot
Or, if you do
grub>ls (hd0,8)
you'll get the filesystem type and UUID.
Another way to see what's under the root:
grub> ls (hd0,8)/
(note the slash, no spaces)
Suppose you see or confirm that the OS you want to boot is on (hd0,8) (= sda8).
Then, you might try to boot that OS using symlinks like this:
grub>set root=(hd0,8)
grub>linux /vmlinuz root=/dev/sda8 ro quiet splash
grub>initrd /initrd.img
grub>boot
But what if you can't remember the kernel options ro quiet splash ?
Then this way will also work:
grub>set root=(hd0,8)
grub>linux /vmlinuz root=/dev/sda8
grub>initrd /initrd.img
grub>boot
(The read-only option, ro, is important, but it is a default option if not specified directly. Thanks goes to dibl for this information.)
Example If you need to re-boot or shut down the PC
To reboot, get the GRUB 2 prompt by pressing "c" key, and then
grub>reboot
To shut down
grub>halt
Example Chainloader
Suppose you had previously installed GRUB 2 to the boot sector of the (hd0,8) partition containing your OS. (You would have done that using sudo grub-install /dev/sda8) Then you may boot that OS using chainloader as follows:
grub>set root=(hd0,8)
grub>chainloader +1
grub>boot
Or,
grub>chainloader (hd0,8)+1
grub>boot
(NOTE about using
the boot command When booting at the grub> prompt, you must use the boot command to make it go. However, in the configuration file /boot/grub/grub.cfg, you do NOT need to use the boot command--it is implied there.)
Re-installing GRUB 2 using Live CD: Key Rescue Method
There are two main ways of doing this: By chrooting into the broken partition and by not chrooting. For the chrooting way, see GRUB 2 Live CD Install Guide:
http://grub.enbug.org/Grub2LiveCdInstallGuide For details about chrooting, see the Appendix in the first post (above).
For "my" way, I'll call "Method 1," of re-installing GRUB2 from a live CD, read on.
Method 1: Installing or re-installing GRUB 2 using a Live CDYour Kubuntu Live CD contains GRUB 2 files; specifically, in a live session, you will find the master GRUB 2 "image" files in /usr/lib/grub/i386-pc. Thus, they can be used to install or re-install GRUB 2. Here's how ...
Start your Kubuntu Live CD.
Choose the option to try Kubuntu without installing.
Open Konsole (Terminal): K-Menu > System > Konsole
Explore your partitions using
sudo fdisk -lu
Determine your root partition. In this example, ours is sda2.
Make a mount point (directory) for partition sda2:
sudo mkdir /media/sda2
Mount sda2 on the mount point:
sudo mount /dev/sda2 /media/sda2
Make a mount point (directory) for /dev:
sudo mkdir /media/dev
Mount the devices in your Live CD session:
sudo mount --bind /dev /media/dev
Install (or re-install) GRUB 2 (into the MBR of drive sda) using the GRUB 2 files in sda2:
sudo grub-install --root-directory=/media/sda2 /dev/sda
You may get this error:
grub-probe: error: Cannot find a GRUB drive for /dev/sda2. Check your device.map.
Auto-detection of a filesystem module failed.
Please specify the module with the option `--modules' explicitly.
If so, try this:
sudo grub-install --recheck --root-directory=/media/sda2 /dev/sda
Maybe you'll get lucky and see this:
Installation finished. No error reported.
This is the contents of the device map /media/sda2/boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.
(hd0) /dev/sda
(=> and so this was successful)
Then, unmount both filesystems:
sudo umount /dev/sda2 /media/sda2
sudo umount /dev /media/dev
Leave Konsole:
exit
Test it:
Exit out of the Live CD, reboot, see if you fixed your booting problem (by booting into the broken partition).
[End of Method 1]
- - - - - - - - - -
Using a Live CD to edit files in your OSThis is done as you would normally do it. Of course, if you wish, you may use Super Grub Disk to boot into your OS and do the editing from there. Here is an outline of a standard way to use your Kubuntu Live CD.
Boot the Live Kubuntu CD, open Konsole, then as root make a directory, mount the filesystem containing the file you need to edit, open that file (possibly as root), edit it, save, quit, unmount the filesystem, exit.
ExampleIf the file you need to edit is called file_name and is on sdb3 (=(hd1,3)), start a Live CD Kubuntu session, open Konsole:
sudo fdisk -lu # to see/check your partitions, if necessary
Make a directory called /media/sdb3:
sudo mkdir /media/sdb3
Mount device sdb3 on directory /media/sdb3:
sudo mount /dev/sdb3 /media/sdb3
Change to that directory:
cd /media/sdb3
Then you may proceed in various ways:
Open Konqueror/Dolphin as root, then open the file_name:
in 8.10 or later: kdesudo konqueror (or dolphin)
in 8.04: kdesu konqueror (dolphin)
Make your edits, then File > Save, File > Quit.
Or, open file_name as root using Kate, then do the edits:
in 8.10 or later: kdesudo kate /path_to file_name
in 8.04: kdesu kate /path_to file_name
Make your edits, then File > Save, File > Quit
Unmount the directory; note the spelling of umount:
sudo umount /media/sdb3
= = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = =
SECTION 4Special Topics Installing GRUB 2 to your PC
grub-install The most useful command The various types of command modes.
"c," grub>, Konsole BASH, edit "e", emu
TAB Completion
How to get information about your drives and devices
At Konsole : sudo fdisk -lu
At the GRUB 2 prompt: grub> ls
Boot menu: Adding or removing an OS entry
Boot menu: Create a custom boot entry
Boot menu: Making your own custom grub.cfg
Boot menu: Changing resolution, text colors, setting background image
4 ways to boot an OS: configfile, symlinks, direct booting, chainloader
Dedicated GRUB 2 partition: How to build it
GRUB 2 Flashdrive: How to build it
Use of the term "root"
GRUB's Root Device, the Linux statement: root=UUID=,
--root-directory=DIR INSTALL_DEVICE
Dual booting: How to set it up
Booting XP on a non-first hard drive: The drivemap command in GRUB 2
Cheat sheet:
GRUB 2 Practical Reminders- - - - -
Installing GRUB 2 To Your PCTo install GRUB 2 to your PC so it boots your PC into your OSs, two steps are required.
1 You need to get the GRUB 2 files installed to your PC, somewhere in the Kubuntu filesystem.
2 Then use those GRUB 2 files to install GRUB 2 to your PC's drives or devices so it can serve as a bootloader to boot your PC into your Kubuntu and your other OSs.
Step 1:
Get the GRUB 2 filesInstall the GRUB 2 package in your Kubuntu OS using your package manager. Or, at Konsole, issue the following command:
sudo apt-get install grub-pc
Check it: Open your file manager (Konqueror or Dolphin or other), and see the GRUB 2 files under
/usr/lib/grub/i386-pc (called the GRUB 2 image directory, and contains a set of "master" GRUB files).
Step 2:
Install the GRUB 2 files so they serve as a bootloaderSuppose your first BIOS boot drive is sda (as seen in Kubuntu using at Konsole the command sudo fdisk -lu). Then, install GRUB 2 to the Master Boot Record of sda:
sudo grub-install /dev/sda
This also copies the GRUB 2 files into /boot/grub.
Then to generate a fresh boot menu configuration file (/boot/grub/grub.cfg), run
sudo grub-mkconfig -o /boot/grub/grub.cfg.
More Details About ThisCAUTION, fair warning:
Have a bootable Super Grub Disk CD handy in case this messes up booting your PC.
To install GRUB 2 files to your PC, open Konsole and run the commands
sudo apt-get update
sudo apt-cache search grub-pc
(returns: grub-pc - GRand Unified Bootloader, version 2 (PC/BIOS version))
sudo apt-get install grub-pc
Then, install GRUB 2 to the Master Boot Record of your first BIOS boot drive. For example, if that MBR is sda, the command would be
sudo grub-install /dev/sda
And then update grub.cfg:
sudo grub-mkconfig -o /boot/grub/grub.cfg
Reboot to see what happens.
The old GRUB may also still be there (in which case you saw an entry on the boot menu to chainload into GRUB 2), in which case you may run
sudo update-from-grub-legacy
to replace GRUB Legacy with GRUB 2 IF YOU WISH TO DO SO.
TroubleshootingInstalling GRUB 2 to the MBR: using
--recheckExample
sudo grub-install /dev/sda
grub-probe: error: cannot find a GRUB drive for /dev/sda.
Auto-detection of a filesystem module failed.
Please specify the module with the option `--modules' explicitly.
So, try this:
sudo grub-install --recheck /dev/sdaInstallation finished. No error reported.
This is the contents of the device map /boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.
(hd0) /dev/sda
- - - - -
[Start subsection]
grub-install The most useful commandFull form: grub-install [OPTION] INSTALL_DEVICE
Two very important options are
--recheck
Probe a device map even if it already exists
--root-directory=DIR
Install GRUB images under the directory DIR instead of the root directory
(See discussion below.)
Examples:
INSTALL_DEVICE may be /dev/sda, /dev/sda1, hd0, hd1, etc.
grub-install /dev/sda installs GRUB 2 to the MBR of drive sda.
grub-install /dev/sda1 installs GRUB 2 to the boot sector of partition sda1.
grub-install hd0 installs GRUB 2 to the MBR of drive hd0.
grub-install --root-directory=/media/sdb1 /dev/sda
sets up GRUB 2 files in the mounted partition /media/sdb1
and then installs GRUB 2 to the MBR of drive sda using /media/sdb1/boot/grub files.
(If there is no /boot/grub directory in sdb1, it will be created and filled with GRUB 2 files.)
grub-install --recheck --root-directory=/media/sdb1 /dev/sda
Do it again, and probe the /boot/grub/device.map (again).
Use the command sudo grub-install for these purposes:
to refresh the entire GRUB 2 installation; or when you are re-installing GRUB 2 to fix a problem; or when you are installing GRUB 2 to another place or to a dedicated GRUB 2 partition or to a USB (flash) drive.
A master script
grub-install is a master script, called a utility, that invokes many other utilities (scripts) to help do its work. You issue this command at Konsole (Terminal) as root (using sudo). It does everything for you; it's a master fix-it-all command.
/usr/lib/grub/i386-pcThe master set of GRUB 2 files in your OS are kept in the GRUB 2 image directory /usr/lib/grub/i386-pc. They get there when you install GRUB 2 to your PC (or OS) using your package manager or using (sudo) apt-get install grub-pc.
grub-install does the following for you:
> The command sudo grub-install copies the GRUB 2 files from /usr/lib/grub/i386-pc to the directory /boot/grub. If /boot/grub does not yet exist, it is created.
> It probes your partition type and partitions (using grub-probe).
> It builds a custom version of core.img for your setup, one of two very important files (along with boot.img). (In GRUB LEGACY terms,, boot.img corresponds to stage_1 and core.img to stage_2.)
> Finally it installs GRUB 2 to your PC so it can boot some OS(s) for you. (It uses grub-setup to do this, setting boot.img in the MBR of your first BIOS boot drive and installs core.img either after the MBR or to a file system (e.g., your OS partition boot sector). See the note below for a few details.)
Two useful options--recheck
Probe a device map even if it already exists
--root-directory=DIR
Install GRUB images under the directory DIR instead of the root directory
--
recheckIf your grub-install command fails, complaining about a filesystem or not finding something, try it again with the option --recheck; like this example:
sudo grub-install --recheck --root-directory=/media/sdb1 /dev/sda
--
root-directory=DIRVery useful. Instead of setting up your GRUB files in /boot/grub under the root directory of your OS, you can use this option to build a /boot/grub directory anywhere, and then use those GRUB 2 files to install GRUB 2 to a hard drive MBR, or to a partition boot sector, or elsewhere (e.g., USB drive or dedicated GRUB 2 partition).
DIR is a directory, and so it is mounted. Thus, if using partition sdb1, for example, you must mount it, as say, /media/sdb1, and then it would be: --root-directory=/media/sdb1.
Dedicated GRUB 2 partitionSuppose your OS is on some partition on one of your hard drives. And suppose you wish to build a dedicated GRUB 2 partition in sdb1, and that your first BIOS boot drive is sda, and that you wish to setup GRUB 2 files in sdb1 and use those to install GRUB to the MBR of sda. Here's the command:
sudo grub-install --root-directory=/media/sdb1 /dev/sda
Note that sdb1 is mounted as /media/sdb1; also that sda is specified as a device: /dev/sda (not just sda).
See the subsection below titled "Dedicated GRUB 2 partition: How to build it"
USB flash driveSuppose your flash drive is seen in Kubuntu as /dev/sdc and it is mounted as /media/flashdrive. Then the command to setup and install GRUB 2 to it is:
sudo grub-install --root-directory=/media/flashdrive /dev/sdc
See the subsection below titled "GRUB 2 Flashdrive: How to build it"
More details at:
grub-install
http://grub.enbug.org/FranklinPiat/grub-install.manpagegrub-setup (You will probably never use this by itself; you will use grub-install and let it do the work for you.)
http://grub.enbug.org/FranklinPiat/grub-setup.manpageA few details about installing boot.img and core.imgGRUB Legacy uses stages: stage_1, stage_1.5, and stage_2. Those are replaced in GRUB 2 by
boot.img (a 512-byte file that corresponds to stage_1 and is installed to a MBR); there is no stage_1.5 in GRUB 2; and
core.img in GRUB 2 takes the place of stage_2 (or, perhaps, of both stage 1.5 and stage_2); it is built specific to your PC setup. The boot.img points at core.img; core.img is embedded in some fixed location (on a disk), but usually that location is in the same "cylinder" as the MBR that contains boot.img. (Details: the MBR goes into sector 1 and is 512 bytes, and that's where boot.img goes. This first cylinder has 63 sectors, so that leaves 62 sectors or 31,744 bytes (=62*512) where core.img may be embedded. This first cylinder (of 63 sectors containing boot.img and core.img) precedes the start of the first partition on that disk, which would start at sector 63 (counting of sectors (in LBA) starts at zero, so 63 sectors take us to the end of sector 62 = the start of sector 63). You will see this if you run as root fdisk -lu.)
[End of subsection: grub-install The most useful command]
- - - - -
The various types of command modes "c," grub>, Konsole BASH, edit "e", emu
When working with GRUB, you must work with root privileges and so you must use sudo and kdesudo. For example, sudo grub-install /dev/sda, kdesudo konqueror, etc.
The command modes you may use in GRUB 2 are the following.
-- Konsole (BASH), in Kubuntu, at your regular prompt (as root), ~#:
-- GRUB 2 emu (from Konsole, issue sudo grub-emu [OPTION]; this gives you a grub> prompt)
=>TODO: More on this later.
-- GRUB 2 command line interface (CLI), grub>.
When you re-boot your PC, get the boot menu, and press the "c" key, you get a GRUB 2 prompt, grub>. That is the GRUB 2 CLI. You will also get "grub>" upon re-booting if you don't have a boot menu, grub.cfg, or if your boot menu is broken. (See SECTION 3, the subsection titled "The GRUB prompt grub> -- What to do with it")
-- Edit mode. Editing on the fly: when you re-boot and see your GRUB 2 boot menu, you can use the "e" key to edit your boot menu on a temporary basis (the edits are not permanent unless you later make them so). (See SECTION 3 -- Editing the boot menu during booting: "e" key.)
=> In all cases, help is nearby, and the commands are generally the same (or nearly so) in all modes, with a few differences.
HelpKonsole BASH CLI:
Appending --help to a command in CLI; for example: grub-mkconfig --help.
GRUB CLI (grub>):
At the GRUB 2 prompt simply type help and press Enter.
To get help with a command, type help <command name>.
Example: grub>help ls tells you about the command ls.
Edit mode:
The key tips are at the bottom of the screen after your press "e"
to enter the edit mode from your on-screen boot menu.
Also, at that point, you can press Control+c to get a grub>,
then type help and/or use TAB completion.
TAB completion (grub>)
While typing after the grub>, try pressing the TAB key and see what happens: in many cases, GRUB will try to help you complete the line with something meaningful or with choices. So type as much as you can recall or type a guess, then press TAB, then you may have to type another guess and press TAB again, and so on until you complete the line the way you want it.
GRUB 2 device numbering is different(hdx,y): hard drive x, partition y
Hard drives start at zero (x=0), same as for GRUB Legacy.
Partitions start at 1 (y=1); in GRUB Legacy, partitions start at zero.
- - - - -
How to get information about your drives, devices, and filesKey: at Konsole
sudo fdisk -lu; and
grub> lsWe'll look at two cases: At the command line in Kubuntu (Konsole); and at the grub> prompt.
Konsole (BASH) command lineExploring your hard drive(s): sudo fdisk -lu => sudo fdisk -lu is
very useful, very important.
GRUB version number: grub-install -v
Drive space: df -h -T
UUIDs (see NOTE below):
blkid (or try sudo blkid); also:
ls /dev/disk/by-uuid/ -alh
grub.cfg, to see it: cat /boot/grub/grub.cfg
fstab (filesystem table), to see it: cat /etc/fstab
Mounting, how filesystems are mounted: cat /etc/mtab or: mount
Boot directory /boot, to find it: df /boot
Kernel version and gcc version (gcc=the GNU compiler used to build the kernel):
cat /proc/version
Kernel version: uname -r
Linux version/name: lsb_release -a
(hold the Shift key and the minus sign key to get _ . LSB = Linux Standard Base)
KDE version (KDE=K Desktop Environment)
for KDE 3.5: kde-config –version and for KDE 4: kde4-config --version
NOTE: UUID = Universally Unique Identifier
Starting with Kubuntu version 8.10, UUIDs are used to identify partitions. A UUID is a 16-byte number (= 128 bits). In canonical form, a UUID consists of 32 hexidecimal digits, displayed in 5 groups separated by hyphens.
At a GRUB prompt, grub>Exploring your hard drive(s):
grub> ls =>
Very useful, very important. (
in GRUB Legacy, the geometry command is used instead of ls)
The ls command is very usefulgrub>ls
gives you a list of your hard drives and partitions as GRUB sees them, in (hdx,y) GRUB 2 device notation.
grub>ls /
shows you the files under the current GRUB 2 root device. You can set that device using set root=. For example:
grub>set root=(hd0,8)
grub>ls /
shows you all files under root. Or: grub>ls (hd0,8)/ .
grub>ls /boot
shows you all files--including kernels--under /boot.
UUIDs and filesystem typegrub>ls (hd0,8)
shows you information about the partition (hd0,8) including its filesystem type and its UUID.
The contents of a directory: grub>ls -l /directoryExample
grub>ls -l /boot
shows you the kernel and initrd files.
(The
option -l indicates "long form" and gives more information. To see all files, including hidden files, use the
option -a: grub>ls -a -l /boot; or grub>ls -al /boot)
GRUB 2 emulation sudo grub-emuAt Konsole, to get a grub> prompt, type sudo grub-emu.
To exit emu and return to Konsole, type exit.
>>>
IMPORTANT sudo grub-emu and then grub>lsWhile you are working at Konsole in Kubuntu, you may need to know how GRUB sees your drives and partitions, the (hdx,y)'s. You can switch into emulation made (sudo grub-emu)) and issue the list (ls) command at the GRUB prompt (grub>ls) to see your drives and GRUB devices. Type exit to return to BASH mode in Konsole.
Using search and catGRUB files, what partitions they are in: grub>search /boot/grub/boot.img
Boot menu, what partition(s) it is in: grub>search /boot/grub/grub.cfg
Kernel, where it is: grub>search /vmlinuz
Boot menu, to see it: grub>cat (hdx,y)/boot/grub/grub.cfg
fstab, to see it: grub>cat (hdx,y)/etc/fstab
Device.map, to see it: grub>cat (hdx,y)/boot/grub/device.map
(NOTE:
In GRUB Legacy, the find command is used instead of search.)
Restart (reboot), or shutdown (halt) your PC at a command line
At Konsole:
sudo shutdown -r now (re-boots the PC)
sudo shutdown -h now (shuts down the PC)
In GRUB:
grub>reboot (re-boots the PC)
grub>halt (shuts down the PC)
- - - - -
Boot menu: Adding or removing an OS entry to grub.cfgRule: You do NOT edit grub.cfg directly. Instead, you work with script files in the folder /etc/grub.d or with settings in /etc/default/grub.
-- Linux operating systems, added automatically
Look at your grub.cfg. The section
### BEGIN /etc/grub.d/10_linux ###
### END /etc/grub.d/10_linux ###
contains Linux operating systems that were automatically detected by GRUB 2 using the script file /etc/grub.d/10_linux. Most of your Linux OSs should be detected this way and included in the boot menu grub.cfg. If not, you can create a custom boot entry (see below, "Boot menu: Create a custom boot entry").
-- Windows and other OSs added automatically
This is done by the script /etc/grub.d/30_os-prober.
-- Adding or removing OSs from your PC. After doing so,
generate a new grub.cfg: sudo grub-mkconfig -o /boot/grub/grub.cfg.
-- Add a boot menu entry by making your own
custom boot entry, then run:
sudo grub-mkconfig -o /boot/grub/grub.cfg
to generate a new grub.cfg.
(See subsection below: "Boot menu: Create a custom boot entry")
-- Removing a boot entry from grub.cfg:
Two choices.
(1) Simply remove the execute bit from the script file in /etc/grub.d that corresponds to (i.e., generates) the boot entry.
Example: If that file is named 43_MyOS-1, then run the Konsole commands
sudo chmod -x /etc/grub.d/43_MyOS-1
sudo grub-mkconfig -o /boot/grub/grub.cfg
(2) Or, remove the script file (for the boot entry) from the folder /etc/grub.d. Then run
sudo grub-mkconfig -o /boot/grub/grub.cfg to generate the new grub.cfg file.
NOTE: If a custom file contains more than one boot entry, you may remove any number of them, leaving the rest. Then use grub-mkconfig to generate your new boot menu, grub.cfg.
Boot menu: Custom boot entryThis is easy, usually.
-- There are 4 ways to make a boot entry (see "4 Ways To Boot an OS").
-- There is a custom template at /etc/grub.d/40_custom.
-- After you write the script file for your custom boot entry, make it executable.
-- Then generate a new grub.cfg by running sudo grub-mkconfig -o /boot/grub/grub.cfg.
Troubleshooting: Sometimes when you run grub-install or grub-mkconfig, it will fail to detect one of your OSs and excludes it from the boot menu grub.cfg. In that case, you could make a custom entry for it (as a script file in /etc/grub.d).
Direct booting To get a model for some of the entries, you have two choices: (1) Get it from your old boot menu (/boot/grub/menu.lst) from GRUB Legacy (if that is available on your PC). Or, it may also be here, made by GRUB 2: menu.lst_backup_by_grub2_postinst. (2) Go into the operating system itself (the one you wish to include), or perhaps access its filesystem using a live CD, and get the information from its own boot menu.
ExampleMaking a custom entry for sidux. Method: Direct booting.
It helps if you have a model for some of the entries. In the old boot menu (/boot/grub/menu.lst) from my GRUB Legacy, I had this boot entry for sidux:
title Debian GNU/Linux, sidux kernel 2.6.28-5.slh.3-sidux-686
root (hd0,2)
kernel /boot/vmlinuz-2.6.28-5.slh.3-sidux-686 root=UUID=306d94a5-107b-4c9e-ae03-a159e18dc1c7 ro quiet vga=791
initrd /boot/initrd.img-2.6.28-5.slh.3-sidux-686
Using a template (e.g., /etc/grub.d/40_custom), create an executable file for the sidux boot entry:
Open an empty text document (as root)
kdesudo kate
Save the new file as, say, /etc/grub.d/41_sidux_sda3
Copy the kernel & initrd lines from menu.lst, change “kernel” to “linux,” adjust the sidux partition number to conform to GRUB 2 convention:
Legacy GRUB: (hd0,2)
GRUB 2: (hd0,3)
Also, double check the UUID for sda3 by running sudo blkid.
Result:
The file /etc/grub.d/41_sidux_sda3 looks like this:
#!/bin/sh
echo "Adding sidux" >&2
cat << EOF
menuentry "sidux on sda3" {
set root=(hd0,3)
linux /boot/vmlinuz-2.6.28-5.slh.3-sidux-686 root=UUID=306d94a5-107b-4c9e-ae03
a159e18dc1c7 ro quiet vga=791
initrd /boot/initrd.img-2.6.28-5.slh.3-sidux-686
}
EOF
The echo statement causes a line to be printed to the screen after executing grub-mkconfig that says “sidux on sda3” so you can see it got done (i.e., that sidux got incorporated into the grub.cfg).
Make the file executable (it is a script, a type of program):
sudo chmod 744 /etc/grub.d/ 41_sidux_sda3
Or,
sudo chmod +x /etc/grub.d/ 41_sidux_sda3
Or, in GUI,
As root, open Konqueror (kdesudo konqueror), access /etc/grub.d, right click on 41_sidux_sda3, Properties, and check the “Executable” box; check Advanced Permission while you are at it.
To incorporate the sidux file 41_sidux_sda3 as a boot entry in the boot menu configuration file /boot/grub/grub.cfg, run
sudo grub-mkconfig -o /boot/grub/grub.cfg
Check that sidux is in your boot menu by opening /boot/grub/grub.cfg.
Boot menu: Making your own custom grub.cfgThis is easy. (For another example, see the subsection below "Dedicated GRUB 2 partition: How to build it.")
Taken directly from
drs305 excellent, detailed guide, GRUB 2 Basics:
http://ubuntuforums.org/showthread.php?t=1195275Building a Totally Customized Menu: Ok, admit you are a control freak and you want to see only what you build yourself - customized titles, no "memtest86+" and no extra kernels. Here is how you do it:
-- Run sudo update-grub [or use grub-mkconfig] to get the current available kernels.
-- Copy the desired "menuentry" listings from /boot/grub/grub.cfg to /etc/grub.d/40_custom The entry begins with the line starting with "menuentry" and ends with a line containing "}".
-- Add any other "menuentry" items you wish to see on the boot menu.
-- Edit the titles of the "menuentry" line if desired (between the quotation symbols). Do not change the lines following the "menuentry" line. Each entry should start with a "menuentry" line and end with a "}" on the last line.
-- Remove the executable bit from /etc/grub.d/10_linux, /etc/grub.d/20_memtest86+ and /etc/grub.d/30_os-prober
Removing the executable bit from any file in /etc/grub.d will exclude the file from being included in GRUB updates. To do it:
sudo chmod -x /etc/grub.d/grub.d/10_linux /etc/grub.d/20_memtest86+ /etc/grub.d/30_os-prober
-- Run "sudo update-grub" [sudo grub-mkconfig -o /boot/grub/grub.cfg]
-- The updated /boot/grub/grub.cfg file should now contain only sections for "00_header", "05_debian_theme" and "40_custom".
-- The grub.cfg file will not be updated with the addition of a new kernel. To add a new kernel, make
"10_linux" executable, run "sudo update-grub" [sudo grub-mkconfig -o /boot/grub/grub.cfg] to refresh the available kernels, and repeat these instructions.
Boot menu: Changing resolution, text colors, setting background imageThe default resolution is 640x480 and applies only to the GRUB 2 boot menu you see when you boot your PC. For changing graphical settings that apply to your boot menu, see kubicle, Reply #30 below.
Boot menu: Background image editing tip for those with widescreen monitorsSee Oceanwatcher, Reply #36 below
4 Ways To Boot an OS configfile, symlinks, direct booting, chainloader
You can use these methods
-- in a boot menu
-- at a grub> prompt (at the GRUB CLI)
to boot OSs. If you use them at the GRUB CLI, you must type
the command boot at the end to make the methods symlinks, direct booting and chainloader work. You do not need the command boot in a configfile menu. You do not need the boot command in grub.cfg (it is implied there).
NOTE: These are done the same as in GRUB Legacy but with a new format.
But see the note on configfile below.
NOTE: Each boot entry starts with a line
menuentry "...some text..." {
and ends with
}
>>>
Configfile bootingThis is easy and flexible; however, there's a
caveat: Both OSs must use the same version of GRUB--both the OS you are working in (where the main boot menu is kept) and the OS you are booting.
For example, consider these two statements in a menuentry:
set root=(hd1,2)
configfile /boot/grub/grub.cfg
An equivalent way of doing it is this:
configfile (hd1,2)/boot/grub/grub.cfg
That tells your GRUB 2 to access partition (hd1,2), find the file /boot/grub/grub.cfg, show you that file so you can make a choice of which OS to boot, then boot the OS you choose. The GRUB doing the work is your native GRUB, the one you are using, not the GRUB in (hd1,2). Your native GRUB must be able to interpret the commands it finds in the grub.cfg of the OS you wish to boot.
When to avoid configfileWhen there is a mixture of GRUB versions on your PC, it is best to avoid using configfile.
Instead, use chainloader or symlinks.
Example (Taken from a grub.cfg. The # sign indicates a comment.)
# Kubuntu 8.04.3 on sdb2, by configfile
menuentry “Kubuntu 8.04.3 on sdb2, by configfile” {
set root=(hd1,2)
configfile /boot/grub/grub.cfg
}
>>>
Symlinks used in a boot entrySymlinks are like shortcuts, and they direct control from the link to the file they point at. Symlinks for the kernel and initrd files are already set up for you. Look for yourself. List all files (-a) in long or detailed form (-l) under your root partition (/) by issuing the following command at Konsole:
ls -a -l /
lrwxrwxrwx 1 root root 33 2009-08-02 11:01 initrd.img -> boot/initrd.img-2.6.24-24-generic
lrwxrwxrwx 1 root root 33 2009-04-19 17:14 initrd.img.old -> boot/initrd.img-2.6.24-23-generic
lrwxrwxrwx 1 root root 30 2009-08-02 11:01 vmlinuz -> boot/vmlinuz-2.6.24-2 4-generic
lrwxrwxrwx 1 root root 30 2009-04-19 17:14 vmlinuz.old -> boot/vmlinuz-2.6.24-23-generic
The symlink for the kernel is vmlinuz, and vmlinuz points at the NEWEST kernel.
The symlink for the initrd is initrd.img, and initrd.img points at the NEWEST initrd.
NOTE: The "l" at the left indicates "link." Note how the links point at their target files following the symbol ->. Note that the
symlinks are stored in your OS at the root level.
NOTE: If you wish to
make a boot entry for the older kernel and initrd, you must use the symlinks for them,
vmlinuz.old and initrd.img.old.
If you use direct booting, you have to write out the exact kernel and initrd names:
linux /boot/vmlinuz-2.6.24-24-generic root=UUID= vb687f89-ggjd-6ach-7755-77241i4b4fk3 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
With symlinks, vmlinuz starts at root and points at vmlinuz-2.6.24-24-generic and initrd.img starts at root and points at initrd.img-2.6.24-24-generic, so you can write more simply,
linux /vmlinuz root=UUID= vb687f89-ggjd-6ach-7755-77241i4b4fk3 ro quiet splash
initrd /initrd.img
However, to simplify this when you are in an emergency trying to boot at the GRUB prompt (grub>), do it this way:
Suppose this OS is Kubuntu 9.10 in (hd0,8) = sda8. Then you'd have
menuentry “Kubuntu 9.10 on sda8, by symlinks” {
set root=(hd0,8)
linux /vmlinuz root=/dev/sda8 ro quiet splash
initrd /initrd.img
}
or even simpler, when you can't remember the kernel options "ro quiet splash":
menuentry “Kubuntu 9.10 on sda8, by symlinks” {
set root=(hd0,8)
linux /vmlinuz root=/dev/sda8
initrd /initrd.img
}
(ro = Read-Only and is the default. Thanks to dibl for this information.)
NOTE about the pathsNotice the paths to the symlinks start at root / (since the symlinks are stored under root /); whereas the paths to the actual kernel & initrd files start at /boot (since the kernel and initrd are stored under /boot)
Another Example
# Kubuntu 9.10 on sdb7 symlinks,
normal modemenuentry “Kubuntu 9.10 on sdb7, by symlinks” {
set root=(hd1,7)
linux /vmlinuz root=/dev/sdb7 ro quiet splash
initrd /initrd.img
}
This is normal mode.
If you want recovery mode (single user),
replace the kernel options “ro quiet splash” with “ro single” (without quotes)
>>>
Direct bootingIn direct booting, you use the actual kernel and initrd file names in the boot menuentry.
NOTE
If you use direct booting at the GRUB CLI, ie., at grub> prompt, you may use TAB completion to make your job easier.
For example,
grub>linux /boot/<Press TAB key now>
and you will get some choices, such as vmlinuz-2.6.24-24-generic
Example
# Kubuntu 8.04 on sdb3, direct booting
menuentry "Kubuntu 8.04 on sdb3, direct booting" {
set root=(hd1,3)
linux /boot/vmlinuz-2.6.24-24-generic root=UUID=db287e84-cbdd-4ca1-8745-85241a3b3fe2 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
}
>>>
Chainloader bootingWhen you boot an OS by chainloading, you use the chainloader command to pass control of the booting from your native GRUB to some other bootloader located in the MBR of a disk somewhere or in the
boot sector of a partition.
NOTE: For this to work, a bootloader must first be installed to the target MBR or a partition boot sector.
A Linux examplemenuentry “Kubuntu 9.10 on sdb7, by chainloader” {
set root=(hd1,7)
chainloader +1
}
"chainloader +1" says to go to sector 1 (of (hd1,7)) and turn control over to the bootloader found there.
For this example to work, a bootloader (e.g., GRUB 2) must be installed to the partition (hd1,7).
To install GRUB 2 to the boot sector of partition sdb7 (=(hd1,7)):
sudo grub-install /dev/sdb7
This is another way to write the same boot entry:
menuentry “Kubuntu 9.10 on sdb7, by chainloader” {
chainloader (hd1,7)+1
}
Another Linux example
menuentry “Drive sdc = hd2 by chainloader” {
chainloader (hd2)+1
}
If a bootloader (e.g., GRUB 2) has been installed to the Master Boot Record of drive sdc (= hd2), the menuentry will boot that hard drive by turning control over to the bootloader in its MBR.
For this example to work, a bootloader (e.g., GRUB 2) must be installed to the Master Boot Record of drive sdc (= hd2). To install GRUB 2 to the Master Boot Record of drive sdc:
sudo grub-install /dev/sdc
Example
Windows XP on sda1
menuentry “Windows XP on sda1, by chainloader” {
set root=(hd0,1)
chainloader +1
}
Dedicated GRUB 2 Partition: How To Build ItAgain, this is straightforward, much easier than in GRUB Legacy.
1 Create the GRUB 2 partition.
Create a partition to be used as your dedicated GRUB 2 partition and format it. I use GParted Live CD to do this. At that time, you may if you wish, again using GParted, set a Label on your partition; e.g., “GRUB2” (without the quotation marks) (in GParted, use Partition > Labels).
(Check the size of the /boot/grub folder to determine how big to make the partition. GRUB 2 files use just 572 KB (96 files, including 12 old ones) on my installation.)
2 Create grub.cfg.
In your home directory, create a text file called grub.cfg and build your custom boot menu for the dedicated GRUB 2 partition. (For a sample, see below.)
(To create the text file, two ways: (1) Right-click on your Desktop, Create New > Text File; or (2) open text editor Kate to an empty document by typing at Konsole kate and save it under the name grub.cfg in your home directory only! To do this as root, use kdesudo kate, but that is not necessary at this point.)
Caution: You may want to completely build your boot menu now and have it ready to go. To make your boot entries in your grub.cfg, see the subsection above "4 Ways To Boot an OS."
3 Install GRUB 2 to the MBR.
From your Kubuntu OS, install GRUB 2 to the Master Boot Record (of your first BIOS boot drive) using GRUB 2 files set up in your dedicated GRUB 2 partition.
Example
Suppose sdb1 is your dedicated GRUB 2 partition, and assume it is mounted as /media/sdb1 (or, if you set the label GRUB2 on sdb1, this might be /media/GRUB2). And suppose you wish to install GRUB 2 to the MBR of sda which is set in BIOS to be your first boot drive.
Do it this way:
sudo grub-install –root-directory=/media/sdb1 /dev/sda
See:
http://grub.enbug.org/FranklinPiat/grub-install.manpage(That will also build the directory /boot/grub for you in your GRUB 2 partition.)
4 As root, copy your grub.cfg from your home directory to the GRUB 2 partition under the folder /boot/grub. (To do this in GUI, open your file manager as root and work from there; e.g., kdesudo konqueror or kdesudo dolphin.)
5 Set the boot flag on your dedicated GRUB 2 partition and re-boot to test it.
Set the boot flag on the dedicated GRUB 2 partition:
Do that using GParted either from your OS (K > System > Partition editor) or from the GParted Live CD. If you do it using the GParted Live CD, you might go this way now:
After completing Step 4 (copying the grub.cfg file into the partition), put the GParted Live CD in the CD tray, let it be recognized, re-boot into GParted Live, set the boot flag on your dedicated GRUB 2 partition (Partition > Manage Flags), GParted > Quit, then double click GParted (large menu at top) to quit and re-boot, when prompted remove the GParted Live CD, and let the PC re-boot (and it will now be using your dedicated GRUB 2 partition), and see if it works.
CAUTION: Remember to keep Super Grub Disk live CD handy.
IMPORTANT NOTE ABOUT KERNEL UPDATES:
Using this method of building a dedicated GRUB 2 partition, YOU are in charge of the boot configuration file /boot/grub/grub.cfg that is located in the GRUB 2 partition. The stuff we talked about above--/etc/default/grub and the scripts /etc/grub.d and grub-mkconfig--does not apply. You must keep these two "shows" separate.
Edit the dedicated GRUB 2 file grub.cfg manually. If there ever is a problem, you may have to manually re-install GRUB 2 to the MBR (of the first BIOS boot drive) from the dedicated GRUB 2 partition.
Example Here's my dedicated GRUB 2 /boot/grub/grub.cfg:
# grub.cfg
# This is my custom boot menu, called /boot/grub/grub.cfg, located in my dedicated Grub 2 partition sda1.
# Set the timeout
set timeout=10
# Set the default boot entry.
set default=0
# Kubuntu 9.10 on sda8 by chainload
menuentry "Kubuntu 9.10 on sda8, by chainload" {
chainloader (hd0,8)+1
}
# Kubuntu 9.10 on sda8 by configfile
menuentry "Kubuntu 9.10 on sda8, by configfile" {
configfile (hd0,8)/boot/grub/cfg
}
# Kubuntu 9.10 on sda8 by symlink
menuentry "Kubuntu 9.10 on sda8, by symlink" {
set root=(hd0,8)
linux /vmlinuz root=/dev/sda8 ro quiet splash
initrd /initrd.img
}
# Kubuntu 8.04.3 on sda2, by configfile
menuentry "Kubuntu 8.04.3 on sda2, by configfile" {
configfile (hd0,2)/boot/grub.cfg
}
# sidux on sda3, by direct booting
menuentry "sidux on sda3" {
set root=(hd0,3)
linux /boot/vmlinuz-2.6.28-5.slh.3-sidux-686 root=UUID=306d94a5-107b-4c9e-ae03-a159e18dc1c7 ro quiet vga=791
initrd /boot/initrd.img-2.6.28-5.slh.3-sidux-686
}
GRUB 2 Flashdrive (USB flash drive)For the principles of installing GRUB 2, see the discussion under "Installing GRUB 2" and "The grub-install Command."
ExampleI used a 1 GB Kingston; the GRUB 2 files used just 51 MB.
Partition and format the flash drive as ext2 (using GParted Partition Editor). (You could also use FAT32 or ext3 or some other filesystem.)
Set the boot flag on the newly created partition (use GParted to do that: Partition > Manage Flags).
Exit GParted. Unplug the flashdrive, then plug it in.
In Kubuntu, to see how it is named, at Konsole run
sudo fdisk -lu
Output:
Disk /dev/sdb: 1031 MB, 1031798784 bytes
255 heads, 63 sectors/track, 125 cylinders, total 2015232 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x000f0fe1
Device Boot Start End Blocks Id System
/dev/sdb1 63 2008124 1004031 83 Linux
Konqueror (or Dolphin) indicated it is mounted as /media/disk.
=> So it is seen as sdb with the partition sdb1 mounted as /media/disk.
Install GRUB 2 to the flash drive. At Konsole:
sudo grub-install --root-directory=/media/disk /dev/sdb
Output:
Installation finished. No error reported.
This is the contents of the device map /media/disk/boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.
(hd0) /dev/sda
(hd1) /dev/sdb
(This is the device.map on the flash drive, /boot/grub/device.map. I will ignore this! Doesn't matter too much. You could edit it as root to read
(hd0) /dev/sda
as seen from the point of view of the flash drive when it is used as a boot drive.)
Let's move on, now ...
Check to see that /boot/grub is created and filled with GRUB 2 files.
Reboot, setting BIOS to boot from the flash drive (USB booting).
The next thing I saw on the screen was:
grub>
I used the GRUB 2 command ls to see my drives and partitions (on the PC):
grub>ls
Since the PC booted from the flash drive, it was seen as hd0 with partition (hd0,1). (The drive that the PC actually boots from is always seen during its booting session as hd0--this is a general fact.)
My regular HDD, normally seen as hd0 was now seen as hd1 and my Kubuntu 9.10 was in (hd1,8).
So, to boot into Kubuntu, I did
grub>chainloader (hd1,8)+1
grub>boot
NOTE:
Previously I had already installed GRUB 2 to the partition boot sector of Kubuntu in case I ever needed to chainload into it. (I used at Konsole in Kubuntu, sudo grub-install /dev/sda8, where sda8 is my Kubuntu partition when there is no other drive attached to the PC.) Had I not already done this, I could could NOT chainload into Kubuntu and would have to boot into Kubuntu in some other way, for example using symlinks:
grub>ls
would show me that Kubuntu is on (hd1,8) when booting from my GRUB 2 flash drive, and so to boot it, I'd do:
grub>set root=(hd1,8)
grub>linux /vmlinuz root=/dev/sda8
grub>initrd /initrd.img
grub>boot
Or, you could do this (if you remembered how!):
grub>set root=(hd1,8)
grub>linux /vmlinuz root=/dev/sda8 ro quite splash
grub>initrd /initrd.img
grub>boot
Thus, I booted into Kubuntu using the GRUB 2 flash drive.
Building a boot menu for the flash drive:
You can create a text file /boot/grub/grub.cfg for the flash drive exactly as demonstrated under building a Dedicated GRUB 2 Partition.
Technical Note: To do so, you will probably have to work as root, say by opening Konqueror or Dolphin as root (kdesudo konqueror), or by opening Kate as root (kdesudo kate). However, you do not necessarily need a grub.cfg on the flash drive. You can simply use it as I did to explore your drives and then boot into an OS. If you do build a grub.cfg for it, you might include the OS(s) on your hard drive(s), and use the GRUB 2 flash drive to boot in emergencies, as you would use Super Grub Disk. Just remember that from the point of view of the grub.cfg on your flash drive, the other drives in your PC are shifted by 1 since upon booting the flash drive, it will be seen as hd0. If adrian15 builds Super Grub Disk for GRUB 2 and includes his usbshift function, then the story changes--for the principle of "USB drive shifting," see my how on building a GRUB flash drive:
-- How To Make GRUB Thumb Drive
http://kubuntuforums.net/forums/index.php?topic=3081748.0[End of the flashdrive subsection]
Use of the Term "root"GRUB's Root Device, the Linux statement, root=UUID=, --root-directory=DIR INSTALL_DEVICE
Example
Consider this menuentry:
### BEGIN /etc/grub.d/10_Linux ###
menuentry "Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic" {
set root=(hd1,2)
linux /boot/vmlinuz-2.6.24-24-generic root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
}
The line
set root=(hd1,2)
sets the GRUB root device. The GRUB root device is the partition containing the kernel vmlinuz and initrd files. Thus, it is the partition containing the directory /boot. Also, since the GRUB boot files are contained in /boot/grub, the GRUB files are in that same /boot partition. Note this part of the linux line: root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44. The UUID corresponds to the partition containing the root filesystem (/) of the OS (in this case, Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic) That partition (identified by its UUID) is passed to the Linux kernel using root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 in the linux line.
So, the line "set root=(hd1,2)" is a message to GRUB 2; and "root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44" is a message to the Linux kernel.
Normally, for most users, the GRUB root partition (location of the kernel & initrd files) is the same as the root partition of the OS. In this case, the GRUB root device (partition) (hd1,2) would be the same as the root of the Kubuntu filesystem (and thus the UUID would be that of (hd1,2)). However, this need not be the case. If you have a separate /boot partition (separate from the root filesystem of the OS), then the
set root=(hdx,y)
statement and the
root=UUID=xxx
statement in the linux line will correspond to two different partitions.
Another use of the word "root" and setting a "root" for GRUB occurs in the statement
sudo grub-install --root-directory=DIR INSTALL_DEVICE; for example
sudo grub-install --root-directory=/media/sdb1 /dev/sda
where DIR is /media/sdb1 and INSTALL_DEVICE is /dev/sda (i.e., the MBR of drive sda). This directs GRUB to install GRUB images to INSTALL_DEVICE (using the files in the GRUB image directory /usr/lib/grub/i386-pc/ of the Kubuntu OS you are working in) under the directory DIR (instead of the root directory (/) of the OS) and then to install GRUB 2 to the MBR of drive sda using GRUB 2 files in /media/sdb1/boot/grub. The directory DIR specified in --root-directory=DIR becomes the GRUB root directory of this specific GRUB installation.
- - - - - - - - - - - - - - - - - - - -
Cheat Sheet
GRUB 2 Practical Reminders -- for those who know what they are doing
Files image:
/usr/lib/grub/i386-pc/boot/grub/grub.cfg Configuration file for the boot menu. Do NOT edit.
/etc/default/grub Default settings file (Timeout, Default OS, kernel options)
/etc/grub.d Folder of boot menu scripts:
00_header; 05_debian_theme: Background, text colors, themes
10_hurd Locates Hurd kernels; 10_linux Locates Linux kernels; 20_memtest86+
30_os-prober: Searches for Linux and other OS's on all partitions
40_custom: Template for custom boot menu entries
More: /boot/grub/device.map,
boot.img (MBR),
core.imgFixing Things, RescueCtrl+Alt+Del reboot PC; Super Grub Disk
New grub.cfg:
sudo grub-mkconfig -o /boot/grub/grub.cfgInstall, re-install GRUB 2:
sudo grub-install [INSTALL_DEVICE]
to MBR: sudo grub-install /dev/sdx; partition: sudo grub-install /dev/sdxn
If error: grub-install
--recheck /dev/sdx; sudo grub-install --recheck /dev/sdxn
Install GRUB 2 to MBR of sda using GRUB 2 in /dev/sdb1/boot/grub:
sudo grub-install –root-directory=/media/sdb1 /dev/sda
Install GRUB 2 to PC (/usr/lib/grub/i386-pc/): sudo apt-get install grub-pc
Live CD rescue: Re-install GRUB 2sudo mkdir /media/sda2 /media/dev
sudo mount /dev/sda2 /media/sda2
sudo mount --bind /dev /media/dev
Install GRUB 2 to MBR of sdb [or to partition sda2] using GRUB 2 files in sda2:
sudo grub-install --root-directory=/media/sda2 /dev/sdb [or /dev/sda2]
umount /media/sda2 /media/dev
Drives, partitions, information sudo fdisk -lu & grub>ls
Naming: (hdx,y) or sdzy: drive x starts at 0;
partitions y start at 1Konsole:
sudo fdisk -lu; df -hT; mounting: cat /etc/mtab; or: mount
UUIDs: sudo blkid; ls /dev/disk/by-uuid/ -alh
Kernel ver: uname -r; cat /proc/version; Linux ver: lsb_release -a
sudo grub-emu and then grub>lsGRUB devices/drives:
grub>ls; grub>ls -al directory
UUID of (hdx,y): grub>ls (hdx,y)
Finding: grub>search /boot/grub/grub.cfg; grub>search /boot/grub/boot.img
Syntax, booting choicesconfigfile: set root=(hdx,y) and configfile /boot/grub/grub.cfg; or:
configfile (hdx,y)/boot/grub/grub.cfg
symlinks: linux /vmlinuz root=UUID= xxx ro quiet splash; initrd /initrd.img
symlinks: linux /vmlinuz root=/dev/sdxn ro quiet splash
chainload: set root=(hdx,y) and chainloader +1; chainloader (hdx,y)+1
chainload a MBR: chainloader (hdx)+1
PermissionsExecutable: sudo chmod 744 /etc/grub.d/
file; Remove: sudo chmod -x /etc/grub.d/
fileRead only, everyone: sudo chmod 444 /etc/grub.d/
fileGUI: kdesudo konqueror (dolphin), rt-click on
file, Properties, Permissions
grub.cfg: sudo chmod +w /boot/grub/grub.cfg; sudo chmod -w /boot/grub/grub.cfg
Create a script called /etc/grub.d/NN_myscript
Empty text doc: kdesudo kate; File > Save As /etc/grub.d/NN_myscript
Type it (see template below).
Make executable: sudo chmod 744 /etc/grub.d/NN_myscript
or, sudo chmod +x /etc/grub.d/NN_myscript
GUI: kdesudo konqueror (dolphin), rt-click, Properties, Permissions
Make new grub.cfg: sudo grub-mkconfig -o /boot/grub/grub.cfg
>
Template, custom boot entry for file /etc/grub.d/NN_name
#!/bin/sh
echo "Adding name" >&2
cat << EOF
menuentry "name of OS boot entry" {
set root=(hdx,y)
linux /boot/vmlinuz-xyz root=UUID=xxx
initrd /boot/initrd.img-xyz
}
EOF
Edit a scriptGUI, kdesudo konqueror, rt-click on script file, Open With Kate/Kwrite.
CLI, kdesudo kate /etc/grub.d/
script_nameEdit the file, File>Save, Exit. New grub.cfg: sudo up-date grub; sudo grub-mkconfig
Flash drive /dev/sdc, sdc1 mounted at /media/disk; set boot flag; install GRUB 2:
sudo grub-install --root-directory=/media/disk /dev/sdc
Separate GRUB 2 partition: mounted at /media/sdb1; sda=MBR of 1st BIOS drive
sudo grub-install –root-directory=/media/sdb1 /dev/sda
Working as root (8.10+: kdesudo; 8.04: kdesu)
kdesudo kate /path-to-file; kdesudo konqueror (or dolphin)
Terminal as root: sudo –i; sudo su
GUI file manager, navigate to file, right-click on file, Actions, Edit as Root.
sudo [COMMAND]; sudo grub-install [INSTALL_DEVICE];
sudo grub-mkconfig -o /boot/grub/grub.cfg
[End of GRUB 2 Practical Reminders]
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Appendix: Techniques--- Installing Kubuntu--GRUB 2 placement
--- Working as root
--- Permissions: read, write, execute; change the execute bit
--- Chroot -- how to
See Part 3 of Commands at Konsole: Beginners: 3 parts
http://kubuntuforums.net/forums/index.php?topic=3091607.0= = = = = = = = = = = = = = = = = = = =
Installing Kubuntu--GRUB 2 placementLive CD method
The Live CD method of installing Kubuntu is easy, fast, and convenient because afterwards, you then have a Live CD to use for rescue and repair of your system.
Installing GRUB 2 filesGRUB 2 is standard on Kubuntu starting with 9.10. During its installation from the Live CD, you can specify if you want GRUB 2installed, and if so, where to put it. Here's how:
Start the Live CD installer.
Step: Disk Setup
"Specify Partitions Manually"
Step: Summary
Advanced button at lower right
Check or un-check to install GRUB 2 bootloader
Choose from the drop-down list where to install GRUB 2
sda = the MBR of drive sda
sda1 = the first partition of drive sda
sdb = the MBR of drive sdb
etc.
Caution:> If you install GRUB to a MBR (sda, sdb, sdc, etc.), it will overwrite any other bootloader already installed to that MBR, and the GRUB 2 from the OS you are currently installing will then control the boot menu you see when you boot up your PC. That is OK, just so you know.
> If you install GRUB 2 to the partition boot sector where you are currently installing the OS (e.g., sdan, for some n=1,2,3,4...), when you re-boot your PC, you will have to manually boot into your new OS you just installed. Do so using chainloader, as follows:
-- Re-boot
-- If you get some boot menu (from a prior Linux OS installation), press the "c" key to get a GRUB prompt, grub>. If you don't get a boot menu but only the GRUB prompt grub>, then that's OK, too.
-- Let's say your new Kubuntu OS was installed to sda9. That is the same as (hd0,9). Then
grub>chainloader (hd0,9)+1
grub>boot
and you will boot into your new OS.
Building new boot menus> In your new OS, you can build a full boot menu simply by doing sudo grub-mkconfig -o /boot/grub/grub.cfg.
> In your existing OSs, you can re-build boot menus to include the new OS the same way:
Konsole
sudo grub-mkconfig -o /boot/grub/grub.cfg
> Worst case, if for some reason that doesn't work, you can make a custom boot entry to include your new OS. See SECTION 4. To get the details of the menuentry for the new OS for the existing grub.cfg, you might have to boot into the new OS and copy details from its grub.cfg. Or, simply boot your new OS using symlinks or chainloader (from another OS's boot menu), for which you do not need any details specific to the new OS. See SECTION 4, "4 Ways to boot an OS."
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Working as rootOpening a text editor (e.g., Kate, Kwrite, etc.) to see the file and/or to edit it:
kdesudo kate path-to-file
Example: kdesudo kate /etc/fstab
Opening an empty text document as root:
kdesudo kate
(then File > Save As)
Opening a file manager as root:
in 8.10 and after: kdesudo konqueror (or dolphin)
in 8.04: kdesu konqueror (dolphin)
Opening a terminal as root:
sudo –i (to get a “root” terminal)
or:
sudo su
Your file manager may support this feature:
Open the file manager, navigate to the file, right-click on the file, Actions, Edit as Root.
At Konsole (BASH) command line: Use sudo.
Example: sudo fdisk -lu
To open a
graphical application (a text editor, a file manager), use either kdesudo or kdesu (see above).
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Permissions: read, write, execute; change the execute bitSee Part 2 of
Commands at Konsole: Beginners: 3 parts
http://kubuntuforums.net/forums/index.php?topic=3091607.0 Ownership and Permissions Use ls -l to see them; chown & chmod to change them.
See tuxfiles
http://www.tuxfiles.org/linuxhelp/filepermissions.html (symbolic mode)
Here's a brief reminder sheet for those who know this stuff:
Setting ownership and permissions in GUIOpen Konqueror or Dolphin as root (kdesudo konqueror), navigate to the file or directory, right-click, Properties, Permission, make changes, OK. In Konqueror/Dolphin, click the Advanced Permissions button to see all choices: owner, group, others and read, write, execute.
CLIowner--group--others
For each class: read, write, execute
ls -l: list files, use a long listing format => shows ownership and permissions
Permissions – numerical mode
There are 8 possibilities (2*2*2) for read (on or off) - write (on or off) - execute (on or off) permissions on a file or directory (2*2*2 = 8 ). The octal equivalents for these binary numbers are:
0: ---; 1: --x; 2: -w-; 3: -wx; 4: r--; 5: r-x; 6: rw-: 7: rwx
744: Owner can do anything, Group can only read, Others can only read
Permissions – symbolic mode
Suppose the file xyzfile is owned by root.
To make it executable for ALL users
sudo chmod +x xyzfile
To remove the execute permission from all users
sudo chmod -x xyzfile
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References and TutorialsNote:
Ubuntu versus Kubuntu tutorialsA GRUB 2 tutorial written for Ubuntu applies to Kubuntu. Watch for obvious differences in a few commands and OS tools. In Ubuntu you will see
gksudo gedit /boot/grub/grub.cfg
used for opening grub.cfg as root using text editor gedit.
In Kubuntu, you would use
kdesudo kate /boot/grub/grub.cfg.
In Kubuntu, you will probably use Konqueror or Dolphin as your file manager. Also, there are different package managers used in each OS, even within the same OS at times! I think you'll be able to sort it out, and you can always post questions under one of the regular Kubuntu forums.
>>> The GRUB commands are the same in both Ubuntu and Kubuntu and other Linus OSs.
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GRUB 2 Bugs and Questions“grub2” package in Ubuntu
https://launchpad.net/ubuntu/+source/grub2Bugs:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bugs?field.status:list=NEWQuestions, Open Questions
https://answers.launchpad.net/ubuntu/+source/grub2/+questions?field.status=OPEN- - - - -
GRUB Legacy-- How To GRUB Methods - Toolkit
http://kubuntuforums.net/forums/index.php?topic=3081671.0The Grub 2 Guide
(formerly Grub 2 Basics)by drs305
http://ubuntuforums.org/showthread.php?t=1195275Absolutely excellent treatment of editing the boot menu and some basic key concepts of Grub 2.
Grub 2 Title Tweaks, by drs305http://ubuntuforums.org/showthread.php?t=1287602Customizing the boot menu. Also by drs305. Editing grub.d scripts.
Grub 2 Manualhttp://grub.enbug.org/ManualWe hope this will be all you need, along with the man pages.
GNU GRUB 1.96/2http://members.iinet.net/%7Eherman546/p20.htmlLooks like an encyclopedic, comprehensive coverage.
GRUB 2 now default for new installations
https://lists.ubuntu.com/archives/ubuntu-devel-announce/2009-June/000573.htmlGrub 2 now default for Ubuntu 9.10
http://www.ubuntugeek.com/grub-2-now-default-for-ubuntu-910-karmic-koala.htmlGRUB 2 -- Ubuntu Wiki -- FrontPage
http://grub.enbug.org/GRUB 2 -- Ubuntu Wiki
https://wiki.ubuntu.com/Grub2FranklinPiat, Wiki -- good stuff
Grub v2 manual, Manpages
http://grub.enbug.org/FranklinPiat/GrubManualGRUB 2, official site
http://www.gnu.org/software/grub/grub-2.en.htmlGNU GRUB, main site, Legacy GRUB
http://www.gnu.org/software/grub/GRUB Wiki: grub.cfg
http://grub.enbug.org/grub.cfgGRUB 2 Commands, GRUB Wiki
http://grub.enbug.org/CommandListCompares GRUB Legacy to GRUB 2 commands.
GRUB 2: Live CD Install Guide
http://grub.enbug.org/Grub2LiveCdInstallGuideStartUp-Manager
https://help.ubuntu.com/community/StartUpManagerGRUB & GRUB 2 Boot Process
http://www.pixelbeat.org/docs/disk/Bootloader
http://en.wikipedia.org/wiki/Boot_loaderGNU GRUB
http://en.wikipedia.org/wiki/GRUBBoot Options
https://help.ubuntu.com/community/BootOptionsKernel Parameters
http://www.kernel.org/doc/Documentation/kernel-parameters.txtGrub Legacy
-- How To GRUB Methods - Toolkit
http://kubuntuforums.net/forums/index.php?topic=3081671.0GParted Live CD
http://gparted.sourceforge.net/livecd.phpFor partitioning, formatting your hard drive.
Super Grub Disk
http://www.supergrubdisk.org/Will boot you into your OS when you can't do it alone.
Arch Linux, ArchWiki GRUB 2
http://wiki.archlinux.org/index.php/GRUB2Experiences in the Community, Jaunty and GRUB2
http://flossexperiences.wordpress.com/2008/11/19/jaunty-and-grub2/GRUB 2 installation
http://www.techenclave.com/guides-and-tutorials/grub-2-installation-92883.htmlGRUB2 Theming
http://ubuntuforums.org/showthread.php?t=1182436KernelTeam/Grub2Testing
https://wiki.ubuntu.com/KernelTeam/Grub2TestingUsing UUID
https://help.ubuntu.com/community/UsingUUIDBIOS Boot Partition, and what does GRUB use it for?
http://grub.enbug.org/BIOS_Boot_PartitionGUID Partition Table
http://en.wikipedia.org/wiki/GUID_Partition_TableTechnical Note TN2166, Secrets of the GPT
http://developer.apple.com/mac/library/technotes/tn2006/tn2166.htmlHOWTO: Booting LiveCD ISOs from USB flash drive with Grub2, by JustRon.
http://ubuntuforums.org/showthread.php?t=1288604Booting LiveCD from HD ISO
http://ubuntuforums.org/showthread.php?t=1295506Boot an iso via Grub 2
http://michael-prokop.at/blog/2009/05/25/boot-an-iso-via-grub2/MultiBoot USB with Grub2 (boot directly from iso files)
http://www.panticz.de/MultiBootUSBGRUB Graphical Menu Development Journal
http://grub.gibibit.com/JournalDebian Wiki, GRUB, grub.cfg
http://wiki.debian.org/Grub/grub.cfg.manpageAs of 9-9-09, it doesn't exist.
Tweaking GRUB 2
http://www.drlock.com/blog/2008/07/11/tweaking-grub-2/GRUB 2 configuration, shirish
http://www.techenclave.com/guides-and-tutorials/grub-2-configuration-93512.htmlHow To Install GRUB 2 On Ubuntu 9.04
http://www.linuxtoday.com/news_story.php3?ltsn=2009-09-02-005-35-OS-HL-SM
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