#!/bin/sh

TODO: Das muss noch entwickelt geteset werden

# It is possible to use a swap file on btrfs, but there are some considerations that need taking care of.
# btrfs filesystem doesn't let to create snapshots if there is a working swap file on the subvolume. That means that it is highly recommended to place a swap file on a separate subvolume.
# Let's assume that the current swap is already off, the / is on /dev/sda1 and Ubuntu is installed with / on @ subvolume and /home is on @home subvolume.
#  Mount /dev/sda1 to /mnt.

   sudo mount /dev/sda1 /mnt

#    If you run ls /mnt, you'll see @, @home and other subvolumes that may be there.

 #   Create a new @swap subvolume.

    sudo btrfs sub create /mnt/@swap

#    Unmount /dev/sda1 from /mnt.

    sudo umount /mnt

#    Create /swap directory where we plan to mount the @swap subvolume.

    sudo mkdir /swap

#    Mount the @swap subvolume to /swap.

    sudo mount -o subvol=@swap /dev/sda1 /swap

#    Create the swap file.

    sudo touch /swap/swapfile

#    Set 600 permissions to the file.

    sudo chmod 600 /swap/swapfile

#    Disable COW for this file.

    sudo chattr +C /swap/swapfile

#    Set size of the swap file to 8G as an example.

    sudo dd if=/dev/zero of=/swap/swapfile bs=1M count=8192

#    Format the swapfile.

    sudo mkswap /swap/swapfile

#    Turn the swap file on.

    sudo swapon /swap/swapfile

# Now the new swap should be working.
#
# You also need to update /etc/fstab to mount all this on boot. Add there two lines:
# uuid from Dev
uuid=$(lsblk -n -o UUID /dev/sda1)
sudo echo "UUID=$uuid /swap btrfs subvol=@swap 0 0 /swap/swapfile none swap sw 0 0" >> /etc/fstab

# The UUID is the one of your /dev/sda1.