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When I installed Ubuntu, I setup an encrypted home partition. Now I have come to an issue where I am running out of memory because I haven't setup swap. How can I setup an encrypted swap file?

A couple of times while booting I've seen some reference to cryptswap. I've also got these lines contained in /etc/fstab

# swap was on /dev/sda6 during installation
#UUID=1ba8a53b-1842-4de7-8e38-2d6c79f3a1ab none            swap    sw              0       0
/dev/mapper/cryptswap1 none swap sw 0 0
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In newer ubuntu-versions (tested 14.10). You have to run /etc/init.d/cryptdisks-early reload @Adam Ryczkowski could you post your startup script? – Jan B Jan 23 '15 at 13:02
up vote 14 down vote accepted

Thanks to this guide I have setup an encrypted swap file (can't be used for hiberation).

  1. Firstly create an appropriately sized (I used 8GB) file to store the swap data.

    truncate -s 4GB /cryptswap

  2. Generate the swap using mkswap.

    mkswap /cryptswap

  3. Install a necessary package. apt-get install cryptsetup

  4. Add the following to /etc/fstab

    /dev/mapper/cryptswap none swap sw 0 0

  5. Add the following to /etc/crypttab

    cryptswap /cryptswap /dev/urandom swap

  6. Activate the new encrypted swap file.

    /etc/init.d/cryptdisks reload

    swapon -a

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This encrypted swap is the only secure option for hibernation. With a little change to /etc/crypttab and a startup script (to ask user for mount password) – Adam Ryczkowski Feb 5 '14 at 15:23
@AdamRyczkowski if you're around, another user was asking for that startup script, if you made one. See comment on the question. – muru Jan 23 '15 at 21:20
@muru On Ubuntu 14.04 there is no need for such script. If I recall correctly, the early booting scripts parse the /etc/crypttab for a line like cryptswap /dev/sda5 none luks and asks the user for a password autmatically – Adam Ryczkowski Jan 24 '15 at 10:39
Instead of truncate use fallocate to allocate inode to file; the mkswap step is useless as it is overwritten later when encrypted swap is setup. – solsTiCe May 28 '15 at 9:49

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