swap

[eddieg538]

When I installed 17.10 I noticed it didn't install a swap. Did Kubuntu get rid of swap or did this install incorrectly?

[Snowhog]

Unless you established/created a swap partition during installation, there wouldn’t be one.

[claydoh]

That depends on which install method was used - one of the automatic options, or manual mode. The automatic on should do so, while if you used manual partition setup, it wont - but if you had an existing swap already on the disk, it would be used automatically when the OS boots as Linux will use whatever swap it finds during startup.

How are you determining that you do not have a swap?

[eddieg538]

I remember when the installation showed it was formatting your disk, in previous installs, it showed sda1 and showed sda4 or 5 as swap but 17.10 did not and I used automatic mode.

[vinnywright]

what dose ,,,,

free -h

and

sudo parted -l

show ?

VINNY

[eddieg538]

free -h
total used free shared buff/cache available
Mem: 3.2G 948M 1.5G 24M 796M 2.1G
Swap: 2.0G 0B 2.0G

sudo parted -l
[sudo] password for ed:
Model: ATA MKNSSDRE1TB (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 1000GB 1000GB primary ext4 boot

[vinnywright]

free -h
total used free shared buff/cache available
Mem: 3.2G 948M 1.5G 24M 796M 2.1G
Swap: 2.0G 0B 2.0G

sudo parted -l
[sudo] password for ed:
Model: ATA MKNSSDRE1TB (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 1000GB 1000GB primary ext4 boot

strange "free" is showing swap ,,,,but parted shows no swap partition ?

what dose

swapon --show

tell ?

VINNY

[eddieg538]

swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 2G 0B -1

[oshunluvr]

swapon --show
NAME TYPE SIZE USED PRIO
/swapfile file 2G 0B -1

There's your answer: In the absence of an existing swap partition the installer is creating a swap file in it's place. This behavior began with 17.04.

Personally, I think the installer should give you the option or at least notification this is going to happen. Obviously, one can select manual partitioning and do this, but if you were unaware that a swap file was going to be used, you'd have to start all over again and re-install. Seems like an unnecessary burden when an option or notification could have been presented before installation is started.

Furthermore, what about COW filesystems like btrfs? I wonder if the installer is programmed to behave correctly in those situations.

[vinnywright]

There's your answer: In the absence of an existing swap partition the installer is creating a swap file in it's place. This behavior began with 17.04.

Personally, I think the installer should give you the option or at least notification this is going to happen. Obviously, one can select manual partitioning and do this, but if you were unaware that a swap file was going to be used, you'd have to start all over again and re-install. Seems like an unnecessary burden when an option or notification could have been presented before installation is started.

Furthermore, what about COW filesystems like btrfs? I wonder if the installer is programmed to behave correctly in those situations.

+1 ,,,I agree 100% on this ,,,in no way should a swap file be created without user intervention !

a warning that no swap was detected and an option to create a swap partition or file maybe , but this kind of decision should be up to the user and could be bad on some file systems .

FROM "man swapon"

You should not use swapon on a file with holes. This can be seen in the system log as

             swapon: swapfile has holes.

      The  swap  file implementation in the kernel expects to be able to write to the file directly, without the assis‐
      tance of the filesystem. This is a problem on preallocated files (e.g. fallocate(1)) on filesystems like XFS or
      ext4, and on copy-on-write filesystems like btrfs.

      It is recommended to use dd(1) and /dev/zero to avoid holes on XFS and ext4.

      swapon  may  not work correctly when using a swap file with some versions of btrfs. This is due to btrfs being a
      copy-on-write filesystem: the file location may not be static and corruption can result. Btrfs  actively  disal‐
      lows the use of swap files on its filesystems by refusing to map the file.

      One  possible  workaround is to map the swap file to a loopback device. This will allow the filesystem to deter‐
      mine the mapping properly but may come with a performance impact.

I think this is a bug in my opinion...that the installer should just do this with no user input !!

VINNY