Creating Swapfile Btrfs

General system Newbie
1

  1. sudo btrfs subvolume create @swap

  2. sudo mkdir /swap

  3. sudo mount -o subvol=@swap /dev/XXX /swap ## replace XXX with your actual partition for example sda2, nvme0n1p2

  4. cd /swap

  5. sudo truncate -s 0 swapfile

  6. sudo chattr +C swapfile

  7. sudo btrfs property set swapfile compression none

  8. sudo dd if=/dev/zero of=swapfile bs=1M count=512 status=progress

  9. sudo chmod 600 swapfile

  10. sudo mkswap swapfile

  11. sudo swapon swapfile

  12. Now Edit the /etc/fstab and add the following two lines:

UUID=NNNN /swap btrfs subvol=@swap ## replace NNNN with the UUID of the partition where @swap resides

/swap/swapfile none swap defaults 0 0

I have been trying to follow the guide above but it seems I am doing something wrong, as far as I see I created the @swap subvolume and its inside / Once I get to the 3rd command its not working the way it is probably supposed to or I am doing something wrong.

nvme0n1 is the drive/partition? I have eos installed on, when I run ls in my root directory after I create the btrfs @swap subvolume I get:

bin   dev  home  lib64	opt   root  sbin  @swap  sys  usr
boot  etc  lib	 mnt	proc  run   srv   swap	 tmp  var

Is @swap supposed to be there?

lsblk:

seb@PrimeCore/ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda           8:0    0 465.8G  0 disk
├─sda1        8:1    0     1K  0 part
└─sda5        8:5    0 465.8G  0 part
sdb           8:16   0 223.6G  0 disk
├─sdb1        8:17   0   500M  0 part
└─sdb2        8:18   0 223.1G  0 part
sdc           8:32   0   1.8T  0 disk
└─sdc1        8:33   0   1.8T  0 part /mnt/diamond-drive
sdd           8:48   0   3.6T  0 disk
└─sdd1        8:49   0   3.6T  0 part /mnt/titan-drive
nvme0n1     259:0    0 931.5G  0 disk
├─nvme0n1p1 259:1    0   300M  0 part /boot/efi
├─nvme0n1p2 259:2    0 922.4G  0 part /var/log
│                                     /home
│                                     /var/cache
│                                     /
└─nvme0n1p3 259:3    0   8.8G  0 part

I tried running the 3rd command from the guide and tried different partitions I dont know what I am doing wrong here…

sudo mount -o subvol=@swap /dev/nvme0n1p2 /swap
mount: /swap: mount(2) system call failed: No such file or directory.
       dmesg(1) may have more information after failed mount system call.              

sudo mount -o subvol=@swap /dev/nvme0n1 /swap
mount: /swap: /dev/nvme0n1 already mounted or mount point busy.
       dmesg(1) may have more information after failed mount system call.

Is this maybe not the best guide or am I more likely doing something wrong?

2

This is the wrong “root”.

That command needs to be run in the root of your btrfs partition which you may not have mounted.

You can mount it like this:

sudo mkdir /mnt/btrfs
sudo mount /dev/nvme0n1p2 /mnt/btrfs -o subvolid=5
3

I dont quite understand this, this is really confusing, once I mount it do I just do cd /mnt/btrfs then create the swap subvolume there?

4

One word is being used for two different things.

The “root” of your filesystem(aka /) is mounted on a subvolume not the “root” of the btrfs partition.

Those instructions want you to create a subvolume at the root of the partition.

Yes. That is correct.

5

sudo mount -o subvol=@swap /dev/nvme0n1 /swap

then I run this while still in the /mnt/btrfs directory? then just continue with the rest of the steps?

6

You can run that command from anywhere.

The rest of the steps should work now.

8 
seb@PrimeCore/swap sudo btrfs property set swapfile compression none swapfile compression none
ERROR: failed to set compression for swapfile: Invalid argument
9

did you double copy/paste there? There is too much command.

10 
1. sudo btrfs property set swapfile compression none
ERROR: failed to set compression for swapfile: Invalid argument

Sorry it just does that in my terminal, something wrong with the terminal due to zsh, I dont know why it does that but the command was entered properly

11

Its actually something to do with alacritty, I switched to konsole and tried the command in that, here is what I get:

seb@PrimeCore~ cd /swap
 seb@PrimeCore/swap sudo btrfs property set ./swapfile compression none
[sudo] password for seb: 
ERROR: failed to set compression for ./swapfile: Invalid argument
 seb@PrimeCore/swap
12

Either type out the command, or paste it in a text editor and edit it before pasting it in the terminal emulator.

13

I think this is actually a btrfs issue/change.

After disabling CoW, the compression property is no longer available.

14

It looks like this step is no longer needed.

btrfs now disables compression when CoW is disabled.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0e852ab8974cd2b5946766b2d9baf82c78ace03d

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