btrfs property set -ts /path/to/snapshot ro (true|false)

https://btrfs.wiki.kernel.org/index.php/Incremental_Backup

btrfs subvolume snapshot -r /mnt/snapshots/@rootfs /mnt/snapshots/$(hostname)-$(date +%Y-%m-%d)

# WRONG: This pushes backups to the backup server. We must pull from the host # to the backup server!

btrfs send -p /home/BACKUP-date /home/BACKUP | \
  ssh root@backups.narf.rocks \
  btrfs receive /backup/hostname.narf.rocks-date --

# UNTESTED

btrfs receive /backup/$hostname-$date < \
  ssh root@$hostname \
  btrfs-send -p /backup/$hostname-$last_backup_date /backup/$hostname-$date