I had swap from a swapfile working for quite some time, but for some reason it stopped working.
sudo fallocate -l 4G /home/.swap/swapfile sudo chmod 600 /home/.swap/swapfile sudo mkswap /home/.swap/swapfile # /etc/fstab /home/.swap/swapfile swap swap defaults 0 0 sudo swapon -a swapon: /home/.swap/swapfile: swapon failed: Invalid argument
I'm running the newest version of Fedora, so is it maybe possible something has changed with an update or what could be the reason?
If you're using btrfs it's important that you create your swapfile without copy-on-write.
Since btrfs version 6.1, a swapfile can be created correctly with this command:
btrfs filesystem mkswapfile --size 2G /path/swapfile For older btrfs versions, you need to create the swapfile like below, where notably the chattr +C disables copy-on-write. It's important to set this attribute before writing anything to the file:
truncate -s 0 /path/swapfile chattr +C /path/swapfile fallocate -l 2G /path/swapfile chmod 0600 /path/swapfile mkswap /path/swapfile Activate it:
swapon /path/swapfile Add it to /etc/fstab with this entry:
/path/swapfile none swap defaults 0 0 I found it documented in the fine material.
sudo blkid) or manipulating a symlink (check ls -l /swapfile). Please try replacing
fallocate -l 4G /home/.swap/swapfile with
dd if=/dev/zero of=/home/.swap/swapfile bs=1M count=4096 Quoting from swapon(8):
Files with holes
The swap file implementation in the kernel expects to be able to write to the file directly, without the assistance of the filesystem. This is a problem on files with holes or on copy-on-write files on filesystems like Btrfs.
Commands like cp(1) or truncate(1) create files with holes. These files will be rejected by swapon.
Preallocated files created by fallocate(1) may be interpreted as files with holes too depending of the filesystem. Preallocated swap files are supported on XFS since Linux 4.18.
The most portable solution to create a swap file is to use dd(1) and
/dev/zero.
The italicized note seems to explain everything. Unfortunately, even with verbose output, swapon doesn't mention the cause (files with holes) of failure.
Quite old question but I just ran into the same problem an nothing that was discussed here worked for me, but i found this in the btrfs filesystem manpage :
mkswapfile [-s size] file Create a new file that's suitable and formatted as a swapfile. Default size is 2GiB, fixed page size 4KiB, minimum size is 40KiB. A swapfile must be created in a specific way: NOCOW and preallocated. Subvolume containing a swapfile cannot be snapshotted and blocks of an activated swapfile cannot be balanced. Swapfile creation can be achieved by standalone commands too. Activation needs to be done by com‐ mand swapon(8). See also command btrfs inspect-internal map-swapfile and the Swapfile feature de‐ scription. NOTE: The command is a simplified version of 'mkswap', if you want to set label, page size, or other parameters please use 'mkswap' proper. Options -s|--size SIZE Create swapfile of a given size SIZE (accepting k/m/g/e/p suffix). -U|--uuid UUID specify UUID to use, or a special value: clear (all zeros), random, time (time-based ran‐ dom) So i did this :
sudo btrfs filesystem mkswapfile --size 12g --uuid clear /swapfile/path
And it worked perfectly
Obviously your filesystem must be btrfs, which is the default in Fedora if I'm not mistaken
Please, check the updated BTRFS filesystem documentation for new kernels (> v.6.1): https://btrfs.readthedocs.io/en/latest/Swapfile.html
It should help you to solve all the problems with making a swapfile on BTRFS.
My setup: Debian 12, kernel v.6.1, btrfs, dm-crypt, SSD
# btrfs filesystem mkswapfile --size 2G swapfile # swapon swapfile As other have noted there is a btrfs variant of creating a swapfile:
sudo btrfs filesystem mkswapfile --size 12g --uuid clear /swapfile/path However, even with this when you go to swapon /swapfile/path you will get the same Invalid argument error. The reason is because in some btrfs configurations you are using more than one device, such as with a Just a Bunch of Disks (JBoD) setup.
My strategy was to allocate a large swapfile on a btrfs volume that was backed by many separate disks. This doesn't seem to be possible using this simple configuration. Instead I am investigating safely resizing each btrfs partition so that each disk has a spare 16GB that can be used as a dedicated swap partition.
swaponprogram, but it can provide more information in its log.sudo.swap. You can write pretty much anything there.swapon: swapfile has holesand the answer below worked.