Below is an elaborate example of an /etc/fstab file, providing everything what is needed to properly bring up a system that is using the default partitioning scheme in combination with the default Btrfs filesystem layout:
/ btrfs noatime,subvol=rootvol 0 0 /home btrfs noatime,subvol=homevol 0 0 /var/swap btrfs noatime,subvol=swapvol 0 0 /var/swap/swapfile none swap sw 0 0
To improve performance, most users would want to add the
noatime mount option, which results in a faster system since access times aren't registered (those are not needed generally anyway). This is also recommended for solid state drive (SSD) users, who may also enable the
discard mount option (ext4 and btrfs only for now) which makes the
TRIM command work.
And this is what the /etc/fstab file would have to look like following the examples given in the instructions, if the main partition has been encrypted with LUKS:
/dev/mapper/main_crypt / btrfs noatime,subvol=rootvol 0 0 /dev/mapper/main_crypt /home btrfs noatime,subvol=homevol 0 0 /dev/mapper/main_crypt /var/swap btrfs noatime,subvol=swapvol 0 0 /var/swap/swapfile none swap sw 0 0
Double-check the /mnt/gentoo/etc/fstab file, save and quit to continue.