#!/bin/sh
#
# References:
#
# "Cohabiting FreeBSD and Gentoo Linux on a Common ZFS Volume"
# https://ericmccorkleblog.wordpress.com/2016/11/15/cohabiting-freebsd-and-gentoo-linux-on-a-common-zfs-volume/
#
# "ZFS Datasets for NixOS"
# https://grahamc.com/blog/nixos-on-zfs
#
# The collective wisdom of libera #zfs.

set -e

POOL=tank
VDEV=/dev/nvme0n1p5
# The OS you are installing first and the root dataset.
OS=gentoo
MOUNT_TARGET=/mnt

if [ "$OS" = freebsd ]; then
    mkdir -p /tmp/bsdinstall_etc
    FSTAB=/tmp/bsdinstall_etc/fstab
else
    FSTAB=/tmp/fstab
fi

# On systems using dkms, you may not want to make /var exec=off.

# NAME                      MOUNTPOINT  COMPRESS    SETUID  EXEC  XATTR   ACLTYPE  DEDUP
FILESYSTEMS='
freebsd                       legacy      lz4         on      on    on     nfsv4    off
freebsd/home                  legacy      lz4         on      on    on     nfsv4    off
freebsd/obj                   legacy      lz4         on      on    on     nfsv4    off
freebsd/tmp                   legacy      lz4         off     on    on     nfsv4    off
freebsd/usr                   legacy      lz4         on      on    on     nfsv4    off
freebsd/usr/include           legacy      zstd        off     off   on     nfsv4    off
freebsd/usr/lib               legacy      lz4         off     on    on     nfsv4    off
freebsd/usr/lib32             legacy      lz4         off     on    on     nfsv4    off
freebsd/usr/libdata           legacy      zstd        off     on    on     nfsv4    off
freebsd/usr/local             legacy      lz4         on      on    on     nfsv4    off
freebsd/usr/local/etc         legacy      zstd        off     on    on     nfsv4    off
freebsd/usr/local/include     legacy      zstd        off     off   on     nfsv4    off
freebsd/usr/local/lib         legacy      lz4         off     on    on     nfsv4    off
freebsd/usr/local/lib32       legacy      lz4         off     on    on     nfsv4    off
freebsd/usr/local/libdata     legacy      zstd        off     on    on     nfsv4    off
freebsd/usr/local/share       legacy      zstd        off     on    on     nfsv4    off
freebsd/usr/local/share/info  legacy      lz4         off     off   on     nfsv4    off
freebsd/usr/local/share/man   legacy      lz4         off     off   on     nfsv4    off
freebsd/usr/ports             legacy      lz4         off     on    on     nfsv4    off
freebsd/usr/share             legacy      zstd        off     on    on     nfsv4    off
freebsd/usr/share/info        legacy      lz4         off     off   on     nfsv4    off
freebsd/usr/share/man         legacy      lz4         off     off   on     nfsv4    off
freebsd/usr/src               legacy      zstd        off     off   on     nfsv4    off
freebsd/var                   legacy      lz4         off     off   on     nfsv4    off
freebsd/var/db                legacy      lz4         off     off   on     nfsv4    off
freebsd/var/db/pkg            legacy      lz4         off     off   on     nfsv4    off
freebsd/var/empty             legacy      lz4         off     off   on     nfsv4    off
freebsd/var/log               legacy      zstd        off     off   on     nfsv4    off
freebsd/var/mail              legacy      zstd        off     off   on     nfsv4    off
freebsd/var/tmp               legacy      lz4         off     off   on     nfsv4    off
gentoo                        legacy      lz4         on      on    sa     posix    off
gentoo/home                   legacy      lz4         on      on    sa     posix    off
gentoo__usr__include          legacy      zstd        off     off   sa     posix    off
gentoo__usr__share            legacy      zstd        off     off   sa     posix    off
gentoo__usr__share/info       legacy      lz4         off     off   sa     posix    off
gentoo__usr__share/man        legacy      lz4         off     off   sa     posix    off
gentoo/tmp                    legacy      lz4         off     on    sa     posix    off
gentoo/var                    legacy      lz4         off     off   sa     posix    off
gentoo/var/db                 legacy      lz4         off     off   sa     posix    off
gentoo/var/empty              legacy      lz4         off     off   sa     posix    off
gentoo/var/log                legacy      zstd        off     off   sa     posix    off
gentoo/var/tmp                legacy      lz4         off     on    sa     posix    off
nixos                         legacy      lz4         on      on    sa     posix    off
nixos/home                    legacy      lz4         on      on    sa     posix    off
nixos/nix                     legacy      lz4         off     off   sa     posix    off
nixos/nix/store               legacy      lz4         on      on    sa     posix    skein
nixos/tmp                     legacy      lz4         off     on    sa     posix    off
nixos/var                     legacy      lz4         off     off   sa     posix    off
nixos/var/db                  legacy      lz4         off     off   sa     posix    off
nixos/var/empty               legacy      lz4         off     off   sa     posix    off
nixos/var/log                 legacy      zstd        off     off   sa     posix    off
nixos/var/tmp                 legacy      lz4         off     off   sa     posix    off
'

umount --recursive $MOUNT_TARGET >/dev/null 2>&1 || :
zpool destroy $POOL >/dev/null 2>&1 || :

# ashift=13 for 8k blocks, use ashift=12 for 4k blocks
#
# Samsung SSDs use physical 8k blocks.
#
# It's ok to use 8k blocks on 4k block devices, but it will use more space for
# small files.
zpool create -f -m legacy -O atime=off -o ashift=13 -o autotrim=on -O checksum=skein $POOL $VDEV

(
    # OS being installed must come first.
    echo "$FILESYSTEMS" | grep    "^$OS" | grep -v '^$'
    echo "$FILESYSTEMS" | grep -v "^$OS" | grep -v '^$'
) | while read -r fs; do
    set -- $fs
    fs=$1 mp=$2 comp=$3 suid=$4 exec=$5 xattr=$6 acltype=$7 dedup=$8

    mnt=${fs#$OS}
    mnt=$(echo "$mnt" | sed 's,__,/,g')
    mnt=$MOUNT_TARGET/${mnt#/}

    zfs create -o mountpoint=$mp -o compression=$comp -o setuid=$suid -o exec=$exec \
        -o xattr=$xattr -o acltype=$acltype -o dedup=$dedup $POOL/$fs

    mkdir -p $mnt

    mount -t zfs $POOL/$fs $mnt

    sys_mnt=${mnt#/mnt}

    echo "$POOL/$fs $sys_mnt zfs rw 0 0" >> $FSTAB
done

echo "proc /proc procfs rw 0 0" >> $FSTAB

zpool set bootfs=$POOL/freebsd $POOL