Swap not working on clean 14.04 install using encrypted home
Known Bug
There is a bug (see below) that overwrites the UUID
for the partition as soon as data is written to it. Therefore, you cannot use the UUID
to reference the partition to use for encrypted swap.
These days, swap space is hardly ever used. On my machine, swap is only used when I open my 40th tab. When I have no swap, suddenly my computer starts lagging and the browser closes itself. Or in the case of the Chromium
browser, a lot of tabs will suddenly 'die'.
For this reason, referencing /dev/disk/by-uuid/
in your /etc/crypttab
might seem to be working for a while, but as soon as your swap space is actually used, it will overwrite the UUID
because the entire partition is used for encrypted data storage.
Easy Fix
The easy fix is to reference the swap partition by device in your /etc/crypttab
, e.g.:
cryptswap1 /dev/sda5 /dev/urandom swap,cipher=aes-cbc-essiv:sha256
Warning: this is probably safe on a laptop (I use it like this), but if you are on a desktop with swappable drives or have other reasons for changing the drive/partition layout, you don't want to do this, as a normal storage partition might suddenly be used for swap.
Note: You need to reboot for this change to take effect, because only when booting will /dev/mapper/cryptswap1
be created.
Proper Fix
The proper way to fix this is to make sure the part of the raw partition that stores the UUID
is not overwritten by encrypted swap data, so it will still be there on reboot. However, I'm not sure where the UUID
is written and how much bytes it takes up. You could, at your own risk, test it like so:
cryptswap1 UUID=abe3c568-c8fd-4dfb-b8e9-0520d442dd61 /dev/urandom swap,offset=36,cipher=aes-cbc-essiv:sha256
Note the offset=36
.
Please if you have an Ubuntu One account log in and go to Bug #1310058 on Launchpad and choose (or click here): "This bug affects me too" so the bug will gain 'popularity' and is more prone to get fixed.
Update 2014-10-27
I also stumbled upon this. Not verified by me. It looks like offset
trick with more verbosity and comments about rebuilding a broken swap.
https://bugs.launchpad.net/ubuntu/+source/ecryptfs-utils/+bug/1310058/comments/22
I was having the same exact problem in Ubuntu 14.04 and came across this thread; this link that mutant provided worked well for me. I used the /dev/disk/by-id
reference rather than the /dev/sdXY, as that reference is not always pointing to the same physical partition. My /etc/crypttab
ended up like:
cryptswap1 /dev/disk/by-id/wwn-0x500...-part6 /dev/urandom swap, cipher=aes-cbc-essiv:sha256
Just use an unencrypted swap
... and keep /home encrypted
I tried a couple of the other solutions suggested here. Even though they kept working after a hot reboot, eventually they all failed after a shutdown and cold restart.
This tells us we are actually dealing with a double bug:
- The UUID of the swap drive gets overridden by the encryption system, and
- There is a timeout issue during booting.
These thoughts are also reflected in the comments to the pertaining bug filed at Launchpad. However, with the pending move from Upstart to systemd, little is done to resolve the bug on current LTS systems.
At this point, the following thoughts crossed my mind:
- During system installation, I asked to only encrypt my
\home
partition, nothing else. - The risks involved with not having an encrypted swap partition are rather limited.
- It is up to Canonical to clean up their act. I will waste no more time with this.
So, here is my solution to restore the swap as a normal, unencrypted swap without having to reinstall the whole operating system.
- If you have not done so already, install
blkid
:$ sudo apt-get install blkid
- Edit
/etc/crypttab
and delete the wholecryptswap1
line:$ sudo nano /etc/crypttab
- Start GParted from the system Settings menu.
- You will see a partition with an exclamation mark. This should be the faulty swap partition.
Carefully select it and reformat it to a
linux-swap
partition. After having applied this operation, you are informed about the new UUID of the restored normal swap partition. You are offered an opportunity to save this information. If you do not, know that you can always retrieve the new UUID from the command line withblkid
:$ sudo blkid
Now, it is time to restore
/etc/fstab
to its old glory:$ sudo nano /etc/fstab
- Remove the entire line containing a reference to
/dev/mapper/cryptswap1
. - Uncomment the old
swap
line by removing the hash#
in front ofUUID=...
. - Now, replace the old UUID with the new one obtained earlier.
- Write the file out by hitting Ctrl+O and exit
nano
with Ctrl+X.
- Remove the entire line containing a reference to
- Once done all that, you can already start using the new unencrypted swap with:
$ sudo swapon -a
- This solution survives both hot reboots and shutdown with cold restart.