Generating swap file on btrfs filesystem

When getting an invalid argument error when doing swapon /swapfile (for instance) it might be due to the underlying filesystem being btrfs. In this case you need to do the following steps:

# truncate -s 0 swapfile
# chattr +C swapfile
# fallocate -l 2G swapfile
# chmod 0600 swapfile
# mkswap swapfile
# swapon swapfile

Since version 6.1 of the btrfs tooling it’s possible to create the swapfile in a single command (except the activation):

# btrfs filesystem mkswapfile --size 2G swapfile
# swapon swapfile

All commands need root permissions (so either with root account or via sudo)