swap problem (swapon: cannot find the device for ...)

[andres.ordonez]

Hi, I recently added the system monitor applet to one of my panels and realised that the swap space is never used. I read the Swap FAQ in the community documentation but couldn't solve the problem.

andres@andres-laptop:~$ cat /proc/sys/vm/swappiness
60

(some appications open)
andres@andres-laptop:~$ free
total used free shared buffers cached
Mem: 3018928 1234988 1783940 0 32364 387884
-/+ buffers/cache: 814740 2204188
Swap: 0 0 0

(many applications open)
andres@andres-laptop:~$ free
total used free shared buffers cached
Mem: 3018928 2994644 24284 0 7408 341180
-/+ buffers/cache: 2646056 372872
Swap: 0 0 0

andres@andres-laptop:~$ sudo fdisk -l

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xc17b6006

Device Boot Start End Blocks Id System
/dev/sda1 1 1275 10240000 27 Unknown
/dev/sda2 * 1275 8924 61439996 7 HPFS/NTFS
/dev/sda3 8925 30401 172514002+ 5 Extended
/dev/sda5 8925 9653 5855661 82 Linux swap / Solaris
/dev/sda6 9654 30401 166658278+ 83 Linux

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x4db9b9e8

Device Boot Start End Blocks Id System
/dev/sdc1 1 121602 976760536 7 HPFS/NTFS


andres@andres-laptop:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
# /dev/sda6
UUID=e154ab05-4256-43fe-ba99-47f94b7f32b7 / ext3 relatime,errors=remount-ro 0 1
# /dev/sda5
UUID=b3790e73-7855-4797-862f-ad8b8a30dcfd none swap sw 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec,utf8 0 0
andres@andres-laptop:~$ sudo swapoff -a
andres@andres-laptop:~$ sudo /sbin/mkswap /dev/sda5
Setting up swapspace version 1, size = 5855656 KiB
no label, UUID=5372e6d3-3e16-4fdf-9902-4eb4fbe3b3d5
andres@andres-laptop:~$ sudo swapon -a
swapon: cannot find the device for UUID=b3790e73-7855-4797-862f-ad8b8a30dcfd

I guess the last line says sums up the problem.

Any help would be very appreciated.

[dabl]

Open a terminal, and paste in this command:

sudo blkid -c /dev/null -o list

and post back with the output.

[dabl]

OK, as you can see, /etc/fstab has a UUID for swap, but the blkid output shows a different UUID.

Open your text editor with root privileges, open /etc/fstab, and carefully replace the UUID number with the correct one from the blkid output. You can copy and paste from the terminal output, but be careful not to include the quote marks in the /etc/fstab line. Don't forget to do File > Save before you exit gedit.

Then issue

sudo mount -a

to mount it, and then you can check it with

sudo mount

, and it should be mounted correctly.

[andres.ordonez]

well I don't really understand the output of mount so here it is:

andres@andres-laptop:~$ sudo mount -a
[1]+ Done sudo gedit /etc/fstab
andres@andres-laptop:~$ sudo mount
/dev/sda6 on / type ext3 (rw,relatime,errors=remount-ro,commit=0)
proc on /proc type proc (rw)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/andres/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=andres)
/dev/sdc1 on /media/TOSHIBA EXT type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096,default_ permissions)

is it ok now?

[andres.ordonez]

I don't think it's ok, the swap space is still 0% in use

[hawkmage]

Why are you concerned that Swap is not being used? Are you running out of physical memory?

Like dabl asked what do you get when you run the command:

sudo blkid -c /dev/null -o list

[andres.ordonez]

Well I posted the output of "sudo blkid -c /dev/null -o list" before, but since I posted it twice by mistake I reported one of the posts for the moderator to delete it, but it seems like both were deleted, anyway here's the output:

andres@andres-laptop:~$ sudo blkid -c /dev/null -o list
device fs_type label mount point UUID
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
/dev/sda1 vfat PQSERVICE (not mounted) EAEE-EB49
/dev/sda2 ntfs ACER (not mounted) 3A240EDB240E99D1
/dev/sda5 swap (not mounted) 4d85d9bf-0085-45fd-96c3-986843bce895
/dev/sda6 ext3 / e154ab05-4256-43fe-ba99-47f94b7f32b7
/dev/sdc1 ntfs TOSHIBA EXT /media/TOSHIBA EXT AEDC9232DC91F535

andres@andres-laptop:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
# /dev/sda6
UUID=e154ab05-4256-43fe-ba99-47f94b7f32b7 / ext3 relatime,errors=remount-ro 0 1
# /dev/sda5
UUID=4d85d9bf-0085-45fd-96c3-986843bce895 none swap sw 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec,utf8 0 0

I don't think I'm running out of physical memory but I'd like to solve it anyway (I'm on vacation hehe)

[dabl]

Hmmm -- where did that second post go?

well I don't really understand the
is it ok now?

Nope.


The UUID of the partition that you are using for swap, apparently /dev/sda5, must be the UUID that is used in the /etc/fstab file to mount it.

The /etc/fstab file that you listed looks right.

Try again in the terminal

sudo mount -a

and then post the output of

sudo mount

[andres.ordonez]

andres@andres-laptop:~$ sudo mount
/dev/sda6 on / type ext3 (rw,relatime,errors=remount-ro,commit=0)
proc on /proc type proc (rw)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/andres/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=andres)
/dev/sdc1 on /media/TOSHIBA EXT type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096,default_ permissions)

[dabl]

Hmmmmmm -- I'm confused!

Can you remove that Toshiba thingy, please? Then, since the UUID of /dev/sda5 has changed twice already, let's have one more look at the output of

sudo blkid -c /dev/null -o list

(just to make sure it hasn't changed again)