Talk:Swap

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Swapfile on BTRFS

Disabling Copy-on-write and compression need to be done in one step on the freshly created file:

'$ sudo chattr +C +m /@swapfile/swapfile

If assigning these attributes in two steps, the second will be rejected.

If creating the subvolume as described - $ sudo btrfs subvolume create /@swapfile - it becomes a sub-subvolume of the actually mounted root /@ - this can be shown by: $ sudo btrfs subvolume list -p /

Today I was restoring a snapshot, TimeShift saved my actual system as a snapshot, and included the /@swapfile subvolume, because that was created as a child-subvolume of /@ - I found not quickly a way to move it out of the snapshot. Addition: When booted externally from Manjaro installation boot media, I could move a subvolume from /run/media/{user}/{mnt-dir}/timeshift.../@/@bsvtest upwards to /run/media/{user}/{mnt-dir}/@bsvtest using root permissions. Yet since the original filesystem root, parent to /@, becomes inaccessible when /@ is mounted to "/", the @swapfile subvolume must be mounted to a directory via /etc/fstab - I named it /@swapfile - see below. The option compress=no is ignored (perhaps because /@ is already mounted with compress=zstd), so chattr +C +m is mandatory.

Before I found the way to move it, I had deleted the swapfile subvolume in .../timeshift.../@/@swapfile (first learned the ID via $ sudo btrfs subvolume list / - then had it deleted by $ sudo btrfs subvolume delete -i {nnn} /) and created the subvolume again as child of parent volume ID 5 - booted from the Manjaro installation media, then mounted my root filesystem in the file manager (XFCE - thunar), where it listed the subvolumes @ @home @cache @log - There I created the subvolume in that path shown in the file manager's address line

'$ sudo btrfs subvolume create /run/media/{user}/{mnt-dir}/@swapfile

And I added actually two lines to /etc/fstab - first one copied from the /@ entry with option compression=no

'UUID=nnn-nnn-nnn-nnn-nnn /@swapfile btrfs subvol=/@swapfile,defaults,discard=async,ssd,compress=no 0 0

and a second for /@swapfile/swapfile as described here in the wiki. Then I followed the described creation procedure for /@swapfile/swapfile once more.