How should I correctly set up my encrypted swap partition? How can I ensure that the setup persists?

I'm running 14.04 using encrypted home folder. I noticed that occasionally my machine would grind to a complete halt for a minute or so. I finally realized that my machine showed that it did not have any swap space set up and my memory was filling up and nothing could be swapped when this happened.

/dev/sda6 is the partition of interest in my case.

How I Made Swap Work Yesterday

I reformatted the swap partition to linux-swap format via gparted and put its UUID, obtained from blkid /dev/sda6, in the appropriate /etc/crypttab entry. I then rebooted the system. Swap file was available and working correctly.

How Swap Stopped Working Again


Steps I've taken to diagnose this situation, things I modified, etc.:

  • free -m shows 0MB total swap space available

    dmays@vipertooth:~$ free -m
                 total       used       free     shared    buffers     cached
    Mem:          5875       2238       3636        270         98       1007
    -/+ buffers/cache:       1133       4741
    Swap:            0          0          0
  • gparted shows the swap partition as "Unknown"

gparted screenshot -- /dev/sda6 is partition of interest

  • blkid /dev/sda6 returns exit code 2.

  • swapon -s shows only column headers

    dmays@vipertooth:~$ swapon -s
    Filename                Type        Size    Used    Priority
  • swapon -a fails with exit code 255

    dmays@vipertooth:~$ sudo swapon -a
    [sudo] password for dmays: 
    swapon: /dev/mapper/cryptswap1: stat failed: No such file or directory
  • modified /etc/crypttab from yesterday

    cryptswap1 UUID=4602a330-ead0-4198-be26-47a5b16666e1 /dev/urandom swap,cipher=aes-cbc-essiv:sha256
  • examined fstab -- it appears my /home may not be encrypted???

    # <file system> <mount point>   <type>  <options>       <dump>  <pass>
    # / was on /dev/sda5 during installation
    UUID=b09ec379-a94d-4905-b4ac-2f5c62b5605d /               ext4    errors=remount-ro 0       1
    # /home was on /dev/sda7 during installation
    UUID=d57bf732-77df-44fe-b547-d15a48dd1857 /home           ext4    defaults        0       2
    # swap was on /dev/sda6 during installation
    /dev/mapper/cryptswap1 none swap sw 0 0

This appears to be a known bug.

Credit to redsandro's answer on a duplicate question for info about the bug and a quick fix for it.

I implemented the "Easy Fix" as stated in the above answer and by user foenhn-2 in a comment to the bug report. Even though this fix is functional I may attempt to get the offset=X method to work in order to keep the swap partition's UUID intact.

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