I am running a custom compiled 3.18.9 kernel and I am wondering about the best way to disable swap on the system. I also use init if it makes a difference.

Is it enough to comment or remove the swap line in /etc/fstab to prevent swap from working/mounting at boot or should I recompile the kernel without Support for paging of anonymous memory (swap) to be 100% sure it does not get enabled?

I run encrypted partitions and want to prevent accidental leakage to the hard disk. My system specifications are also great enough that I can survive in a swap-less environment.

  • Why isn't your swap encrypted? Apr 22 '15 at 18:46
  • @MichaelHampton I didn't see a need at the point in time until I realized what was eventually going to happen. Plus my system doesn't reach a point in any time that the swap was used, so I feel I am free to remove it.
    – user283167
    Apr 22 '15 at 19:09
  • I'd remove the feature from the kernel then. Otherwise someone can plug an USB-stick and start swapping to it again.
    – ott--
    Apr 22 '15 at 21:03
  • @ott Doesn't the user require super user access to use the swapon/swapoff executable? I might disable it again just in case, but I am uncertain a unprivileged user can create swap files.
    – user283167
    Apr 22 '15 at 21:32
  • Indeed, he needs super user access, which he could with an exploit e.g.. But are you watching your server 24/7?
    – ott--
    Apr 22 '15 at 21:44
  1. Identify configured swap devices and files with cat /proc/swaps.
  2. Turn off all swap devices and files with swapoff -a.
  3. Remove any matching reference found in /etc/fstab.
  4. Optional: Destroy any swap devices or files found in step 1 to prevent their reuse. Due to your concerns about leaking sensitive information, you may wish to consider performing some sort of secure wipe.

man swapoff

  • 2
    On some systems you must also rebuild the initrd archive, e.g. with dracut --regenerate-all --force or mkinitrd, or the system will not boot. Thanks to J.O. Aho and Carlos E.R. on alt.os.linux.suse.
    – Ant_222
    Dec 19 '18 at 9:06
  • Something along sudo sed -i '/\tswap\t/d' /etc/fstab to automate it. Jun 7 at 9:08

It used to be that only swap partitions in /etc/fstab were used automatically, however, systemd may be changing that slightly. You might need to do:

systemctl mask dev-sdXX.swap

(change sdXX) to your real formatted swap partition, which, begs the question of why you have a swap partition if you don't want it used...

If you are not using systemd, then, removing the swap entries from /etc/fstab should be sufficient (as far as I know).

Maybe the real solution is to get rid of the swap partitions, so they won't be used accidentally. To remove the swap partitions, I would use fdisk to change the partition type from swap to something else, and then reformat the partition or use: dd if=/dev/zero of=/dev/old-swap-partition in order to zero it out and prevent its use.

See also Set up use of swap partition with systemd.

  • 1
    I still use init via openRC, I purposefully purged systemd from the install. And as for the swap question, I was doing a regular install until I made the decision to use cryptsetup/luks to mount encrypted files formatted to ext4 over top of my filesystem. If you could be so kind to touch upon the way to disable swap when using init I would appreciate it.
    – user283167
    Apr 22 '15 at 19:14
  • Also, it could be systemctl mask swapfile.swap.
    – dess
    Jan 28 '20 at 15:49

If you are really sure you want to disable swapping (note: this is not recommended, even where you are pretty sure that physical RAM is more than enough), follow these steps:

  1. run swapoff -a: this will immediately disable swap
  2. remove any swap entry from /etc/fstab
  3. reboot the system. If the swap is gone, good. If, for some reason, it is still here, you had to remove the swap partition. Repeat steps 1 and 2 and, after that, use fdisk or parted to remove the (now unused) swap partition. Use great care here: removing the wrong partition will have disastrous effects!
  4. reboot
  • 1
    Why is it not recommended to disable swap even if you have enough ram?
    – Rolf
    May 6 '18 at 11:24
  • 1
    Because Linux proactively uses the swap partition to free more memory for caching. This can improve performance. Anyway, it is a tunable parameter. For more information, read here. Moreover, an improvvise surge in memory allocation in a swapless system can trigger the kernel OOM killer.
    – shodanshok
    May 6 '18 at 22:03
  • 3
    Thanks, this is reasonable. Nevertheless, I was thinking that if "enough ram" (eg: 8 or 16 GB) is full then it is likely some kind of exceptional situation (application with a memory leak or some other runaway issue, DDOS attack, etc.) in which case even swap would eventually be overwhelmed anyway. Maybe I'm not making a very convincing argument however this should not happen in light-ish desktop use.
    – Rolf
    May 8 '18 at 16:23
  • 1
    What about SSD drives wearing out due to use of swap? Jan 31 '20 at 2:46
  • @PeterMortensen while possible, it seems an highly unlikely outcome, especially if using a quality TLC drive.
    – shodanshok
    Jan 31 '20 at 6:44

On Raspbian 10 (Buster), the clean answer would be:

To disable it until the next reboot, as stated in */etc/fstab*:

sudo /sbin/dphys-swapfile swapoff

To disable swap on boot:

sudo systemctl disable dphys-swapfile

(It turns out I couldn't find that information anywhere...)

  • Thank you very much. could not work this out for the life of me
    – Erik K
    May 9 '20 at 18:44

On my Linux Mint box (version 19.3 (Tricia), based on Ubuntu 18.04 (Bionic Beaver)) without a swap partition or without any swap at all, systemctl reported that swapfile.swap failed during every start. It could be disabled with the command:

sudo systemctl disable swapfile.swap

The swapfile.swap is a 'special' part of systemd, which you can read about in man, using the man systemd.special command.


When I view the /etc/fstab file on Raspbian I see a comment saying

a swapfile is not a swap partition, no line here
  use dphys-swapfile swap[on|off] for that

But to completely disable the preconfigured swap file this works perfectly fine:

swapoff -a
chmod -x /etc/init.d/dphys-swapfile

This solution looks a bit quick and dirty to me, however, you can simply reenable it with:

chmod +x /etc/init.d/dphys-swapfile

I know this is probably not the right answer for THIS question, but to be complete: If you just want to prevent starting swapping on SOME devices at boot, without removing them from fstab, you can add noauto as a flag after sw (sw,noauto).

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