Installation working but confusing information

[Worzel]

Intended set-up was @/boot/efi and @/ (btrfs) as a learning exercise, admittedly years too late!
I have no problems using the system and updates etc all run ok. Then I read about merging @/home into @/ but

partition manager doesn't show @/home, which I took as meaning installation was just efi + root

However ... lsblk doesn't show @/ and /etc/fstab shows both ?


As said, everything seems to work but the above have me confused (nothing new there)!!

[Snowhog]

Normal (re: non-btrfs specific commands) won't show the btrfs volumes/subvolumes. That's by design.

In a konsole you can type: sudo btrfs subvolume list /

See also: https://www.thegeekdiary.com/btrfs-c...s-file-system/

[claydoh]

"@" indicates btrfs file system volumes, not physical drive partitions. And mounts (things in fstab, for example) are not necessarily physical devices (which is what lsblk shows, and what partition manager ....manages) . Not sure how to define what a volume means tbh, other than they don't necessarily have a set size (other than the size of the partition they reside in), while physical partitions do.

Use the mount command to view vastly more confusing info on all the things actually mounted, most of which are not physical devices at all.

[jlittle]

Use the mount command to view vastly more confusing info on all the things actually mounted, most of which are not physical devices at all.

For a somewhat less confusing list, one can use

findmnt --real --types nosquashfs

(nosquashfs is to suppress snap mounts; not necessary if you've got rid of snaps.)

[claydoh]

For a somewhat less confusing list, one can use

That's no fun But noted, and an alias created

[Worzel]

So I ran it and it seems I have a working system but apparently without root!!


Downloaded Neon installation to usb and went through to partitioning which showed my ssd with /boot/efi and / only. Why /home appears instead I have no idea but assume a technical faux pas ( cock-up ) has been made somewhere.

I assume simplest solution is to re-install but do it correctly?

[claydoh]

So I ran it and it seems I have a working system but apparently without root!!

Um.... / /dev/sda2 [/@] btrfs <-----this is your root ("/")

There is nothing wrong with your system . Both /@ and /@home are subvolumes that are sharing the available space on your BTRFS partition (/dev/sda2)
Confusing and complex a bit, for sure, but you do not need to reinstall or anything.

[oshunluvr]

To add to what's been said re. btrfs, if you do a "df" to see your volume sizes, you will see that your root and home file systems have exactly the same "Filesystem" location (in your case /dev/sda2) and size-used-free amounts. This is how btrfs works using subvolumes.

Breaking it down a bit:
/dev/sda is your first hard drive
/dev/sda2 is the second partition on the first hard drive
/dev/sda2 contains a btrfs filesystem
@ and @home are btrfs subvolumes that exist on the file system that resides on /dev/sda2

You access these subvolumes separately by virtue of the fact that they (the subvolumes) are mounted in the same way a file system is. So @ is mounted at / and @home is mounted at /home, and you never really "see" the subvolume names themselves except in /etc/fstab where the mount information is stored.

A btrfs file system segregates data in the same way using two separate file systems does, except since the subvolumes reside in a single file system so all free space is shared across all the subvolumes - which explains why / and /home show the same exact sizes.

You can, and will probably want to, access the subvolumes directly so you can make snapshots and backups of them. To do this you must mount the "root" btrfs file system. To do this, create a mount point and mount the whole file system rather than a subvolume, like this:

sudo mkdir /mnt/subvols
sudo mount /dev/sda2 /mnt/subvols
ls /mnt/subvols

The results from the "ls" command will be:

@ @home
You can now make a snapshot of the root subvolume like so:

sudo btrfs su sn /mnt/subvols/@ /mnt/subvols/@snap1

Now "ls /mnt/subvols" will reveal:

@ @home @snap1

I suggest do some reading about btrfs and how (and why) to make snapshots and backups of your subvolumes. They can be a life saver.

[Worzel]

Will do, and thanks