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I am on Ubuntu 12.04, Thinkpad Edge 13, encrypted home. A message in the System Monitor tells me that swap is "not available". I can get it back using the swapon option in gparted (I thought I could also do sudo swapon -a in a terminal, but that does not work). The problem is that I have to swapon after every reboot. How can I switch it back on so it stays on even after a reboot?

my fstab:

# # <file system> <mount point> <type> <options> <dump> <pass> 
proc /proc proc nodev,noexec,nosuid 0 0 
# / was on /dev/sda5 during installation 
UUID=47641b93-9d12-4e6a-b803-dde28f0e5725 / ext4 errors=remount-ro 0 1
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Can you post your /etc/fstab? –  cadadr Oct 12 '12 at 10:58
    
# /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/sda5 during installation UUID=47641b93-9d12-4e6a-b803-dde28f0e5725 / ext4 errors=remount-ro 0 1 –  geoffrey Oct 12 '12 at 13:37
    
You realise the two UUIDs you posted above are actually different? There's a "-8" missing after the "4aa8" block in the swapon response (and I suppose in fstab as well). –  user148539 Apr 11 '13 at 13:02

2 Answers 2

up vote 8 down vote accepted

You have no configuration for swap in /etc/fstab. Add following line to that file:

UUID=<uuid> none   swap    sw    0       0   

You have to replace <uuid> with the uuid of your swap partition. To do that, run sudo blkid

$ sudo blkid
/dev/sda1: LABEL="System Reserved" UUID="88A0D0A1A0D09752" TYPE="ntfs" 
/dev/sda2: UUID="0620D9F920D9EFA3" TYPE="ntfs" 
/dev/sda5: UUID="c282b418-2045-4852-8789-88a44360a0bb" TYPE="ext4" 
/dev/sda6: UUID="f99c6a0c-790a-45ca-a1a9-8874f5a2999b" TYPE="ext4" 
/dev/sda7: UUID="4cc2e909-ebd1-4c72-abee-aa32035bf330" TYPE="swap"

This is a list of my partitions, and as you see, /dev/sda7 is my swap partition. So you can copy the value of UUID corresponding to your swap, omitting the quotes, and use it for your fstab file.

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It worked. Thanks!! –  geoffrey Oct 12 '12 at 19:13
    
You're welcome :)) –  cadadr Oct 12 '12 at 19:15

After the upgrade to 12.04, certain little anomalies occurred. I was unaware my swap partition wasn't working until I tried to open a large file in Gimp.

blkid shows:

/dev/sdb6: UUID="3e0550cf-4a55-4aa8-80fa-24103c1b25a7" TYPE="swap" 

but it is not active according to System Monitor. The UUID was definitely right but no go ... not sure how I got to this command:

blkid -p /dev/mapper/foo-swap_1
error: /dev/mapper/foo-swap_1: No such file or directory

File manager showed me a 0 byte icon, filename control, -- so what was supposed to be written there? By what?

sudo swapon --all --verbose yielded
swapon: cannot find the device for UUID=3e0550cf-4a55-4aa80fa-24103c1b25a7

I edited the /etc/fstab file adding

/dev/sdb6   none    swap    sw  0   0

Reboot and System Monitor shows it active.

This was the first site I found for help; in my case, the UUID did not work even though it was in fstab, so there is something missing 'in the middle'. This may help someone, who knows.

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