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Setting up Opt in BTRFS

Inspired from this excellent blog post.

Variables

DISK_BOOT_SIZE_MB=512
DISK_SWAP_SIZE_GB=4
DISK=/dev/vda

Wipe and Partition Disk

wipefs "${DISK}" -a -f
sgdisk --zap-all "${DISK}"
sgdisk --clear \
                --new=1:0:+"${DISK_BOOT_SIZE_MB}"MiB --typecode=1:ef00 --change-name=1:EFI \
                --new=2:0:+"${DISK_SWAP_SIZE_GB}"GiB --typecode=2:8200 --change-name=2:swap \
                --new=3:0:0 --typecode=3:8300 --change-name=3:pool0_0 \
                "${DISK}"

Create Encrypted Disk

cryptsetup --verify-passphrase -v luksFormat "${DISK}"3
cryptsetup open "${DISK}"3 pool0_0
mkswap "${DISK}"2
swapon "${DISK}"2
mkfs.btrfs /dev/mapper/pool0_0

Create BTRFS Subvolumes

mount -t btrfs /dev/mapper/pool0_0 /mnt
btrfs subvolume create /mnt/root
mkdir -p /mnt/home
btrfs subvolume create /mnt/home/active
btrfs subvolume create /mnt/home/snapshots
btrfs subvolume create /mnt/nix
btrfs subvolume create /mnt/persist
mkdir -p /mnt/var_local
btrfs subvolume create /mnt/var_local/active
btrfs subvolume create /mnt/var_local/snapshots
btrfs subvolume create /mnt/var_log

Take a readonly snapshot of the root subvolume, which gets rolled back to on every boot.

btrfs subvolume snapshot -r /mnt/root /mnt/root-blank

Mount Subvolumes and Partitions

umount /mnt
mount -o subvol=root,compress=zstd,noatime /dev/mapper/pool0_0 /mnt

mkdir -p /mnt/home
mount -o subvol=home/active,compress=zstd,noatime /dev/mapper/pool0_0 /mnt/home

mkdir -p /mnt/nix
mount -o subvol=nix,compress=zstd,noatime /dev/mapper/pool0_0 /mnt/nix

mkdir -p /mnt/persist
mount -o subvol=persist,compress=zstd,noatime /dev/mapper/pool0_0 /mnt/persist

mkdir -p /mnt/var/local
mount -o subvol=var_local,compress=zstd,noatime /dev/mapper/pool0_0 /mnt/var/local

mkdir -p /mnt/var/log
mount -o subvol=var_log,compress=zstd,noatime /dev/mapper/pool0_0 /mnt/var/log

mkdir -p /mnt/boot
mount -o defaults,nosuid,nodev,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro /dev/disk/by-partlabel/EFI /mnt/boot
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