Generic

BTRFS Support

1. Grow FS via systemd on boot and disable access times:

   Add x-systemd.growfs and noatime to /etc/fstab.

   Example:

   /dev/mapper/dmroot  /    ext4  defaults,discard,noatime,x-systemd.growfs  1  1
   /dev/xvdb           /rw  auto  noauto,defaults,discard,noatime,x-systemd.growfs    1  2

   Qubes has a built-in mechanism for resizing the FS on boot but it is limited to ext4.

   Note

   When converting to BTRFS, also replace ext4 by btrfs.

2. (Re)mount FS with discard=async:

   Create /etc/systemd/system/qubes-btrfs-remount@.service:

   [Unit]
   Description=Set custom mount options on BTRFS
   After=%i.mount
   Requisite=%i.mount
   ConditionKernelVersion=>=5.6
   
   [Service]
   ExecCondition=findmnt -t btrfs /%I
   ExecStart=mount -o remount,discard=async /%I
   
   [Install]
   WantedBy=multi-user.target
   

   Enable for /:

   systemctl enable qubes-btrfs-remount@-.service
   

   Enable for /rw/:

   systemctl enable qubes-btrfs-remount@rw.service