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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, 2015 at 13:02

2 Answers 2

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Thanks to this guide I set up an encrypted swap file (can't be used for hibernation). On Debian based distributions, you will need the cryptsetup package for these instructions.

  1. Firstly create an appropriately sized file (here 4 gigabytes) to store the swap data:

    fallocate -l 4G /cryptswap
    
  2. Add the following to /etc/crypttab:

    cryptswap /cryptswap /dev/urandom swap
    
  3. Activate the newly created encrypted drive:

    service cryptdisks reload
    
  4. Add the following to /etc/fstab:

    /dev/mapper/cryptswap none swap sw 0 0
    
  5. Activate the new swap file:

    swapon -a
    
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  • 2
    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) Feb 5, 2014 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, 2015 at 21:20
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    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, 2015 at 9:49
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    Nice summary. However, anyone wanting to read more will find that your link "this guide" is dead. Jul 28, 2016 at 20:06
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    Just a note: I had to reboot the system before the /dev/mapper/cryptswap volume appeared.
    – HRJ
    Dec 1, 2016 at 6:30
6

Skip the reboot:

sudo cryptdisks_start cryptswap

where cryptswap is the name in /etc/crypttab

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  • 2
    I don't understand how that addresses the question. Could you please explain? As far as I understand it, OP wants to know how to set up (encrypted) swap space properly. Your answer just describes how to start a previously defined encrypted volume but not how to use it for swapping. -1 Mar 6, 2017 at 22:10
  • rise, o ancient thread. Friendly is trying to address what HRJ mentioned as a comment added to the OP. Namely, "I had to reboot the system before /dev/mapper/cryptswap volume appeared." This handy cryptdisks_start swap0 (in my case) saved me from having to reboot. noice.
    – fbicknel
    Sep 28, 2021 at 20:58

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