Ubuntu – Swap vanished after reboot

encryptionformatswap

I have installed Kubuntu 14.04 with an encrypted home directory. Although I had swap set up during the install, the swap space was not there after installing. This has happened to many people, there seems to be a bug somewhere. I googled and found a solution to this
here.

I followed the steps there, leaving out the ones that had to do with resume, because that is disabled on my install anyway. So I essentially did:

sudo swapoff -a (turns off swap)
comment existing swap configuration in /etc/crypttab
comment existing swap configuration in /etc/fstab
re-format swap partition with gparted as linux-swap
sudo mkswap /dev/sdXX 
sudo swapon /dev/sdXX 
sudo ecryptfs-setup-swap

Then I had a working swap and was happy, until I rebooted my laptop and was back to square one.
Looking at the partition with gparted, it says file system unknown for the (former) swap partition, and needless to say I don't have any swap space available.

So, now my question is: Why did the file system formatting (as linux-swap) not survive the reboot? Is there anything I can do about that?

If I do blkid, the swap partition does not show up at all, so my problem seems to be different from this question.

Edit: Still working on it, so I did the above procedure again, after which /etc/crypttab looks like this:

cryptswap1 UUID=xxxx /dev/urandom swap,cipher=aes-cbc-essiv:sha256

plus some lines that are commented out. And /etc/fstab contains this line:

/dev/mapper/cryptswap1 none swap sw 0 0

Both new lines however look exactly the same (apart from the UUID) as what was generated the last two times. So I don't have great hopes that it will stay when I reboot.
Gparted now shows the partition I am using as linux-swap. (Before rebooting)
Also blkid gives this line:

/dev/sda7: UUID="xxxx" TYPE="swap"

I tested the swap and it works, i.e. I started a program that used a lot of memory and checked how much was loaded into swap in the system monitor.

Edit2: Turns out that 3 is not the magic number that fixes this issue. The content of the two files is unchanged, blkid does not show the line with /dev/sda7 anymore and gparted shows the swap partition as "unknown".

Any suggestions the output of what I could look at or what else I could try are really welcome. My workaround at the moment is to just not reboot, but sometimes when there is an update, my laptop really wants to reboot.

Edit3: Is there really nothing else one could try to fix this? Any commands I could try? Any output I could look at?

Best Answer

This is not happening in the reboot. After you finish your setup (running ecryptfs-setup-swap), go back to gparted and reload the table & open a terminal and run: sudo fdisk -l /dev/sda. You gonna find that partition still having Id 83 Linux Swap and became in Unknown format.

Why is that?! It became an encrypted partition already.

In /etc/fstab:

  • Old swap partition was commented.

  • New mapped one inserted:

    /dev/mapper/cryptswap1 none swap sw 0 0

This is fine.

In /etc/crypttab:

  • A new line added to map the swap:

    cryptswap1 UUID=xxxx /dev/urandom swap,cipher=aes-cbc-essiv:sha256

But there is something wrong here, Does an encrypted partition have a UUID (non-encrypted)?!!!

  1. So set the dev path directly as this example:

    cryptswap1 /dev/sdXX /dev/urandom swap,cipher=aes-cbc-essiv:sha256

  2. Reboot then the Swap will be on.

BTW, This should be reported as a bug. ecryptfs-setup-swap should use device path instead of uuid.

Update: I could find same answered question which include the bug report too.

It contains the canonical answer by adding an offset= in the crypttab options.

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