genfstab

#!/bin/sh
#
# Chimera Linux fstab(5) generator, mostly compatible with arch genfstab
#
# Copyright 2023-2024 q66 <q66@chimera-linux.org>
#
# License: BSD-2-Clause
#

readonly PROGNAME=$(basename "$0")

msg() {
    printf "\033[1m$@\n\033[m"
}

die() {
    msg "ERROR: $@"
    exit 1
}

usage() {
    cat << EOF
Usage: $PROGNAME [opts] root

Options:
  -p      Do not include pseudo-filesystems (default).
  -P      Do include pseudo-filesystems.
  -L      Use labels for identifiers (-t LABEL).
  -U      Use UUIDs for identifiers (-t UUID).
  -t TAG  Use TAG for identifiers (LABEL, UUID, PARTLABEL, PARTUUID).
  -h      Print this message.
EOF
    exit ${1:=1}
}

INC_PSEUDOFS=0
IDTAG=

while getopts "pPLUt:h" opt; do
    case "$opt" in
        p) INC_PSEUDOFS=0 ;;
        P) INC_PSEUDOFS=1 ;;
        L) IDTAG=LABEL ;;
        U) IDTAG=UUID ;;
        t) IDTAG=$(echo "${OPTARG}" | tr '[:lower:]' '[:upper:]') ;;
        h) usage 0 ;;
        *) usage 1 ;;
    esac
done

shift $((OPTIND - 1))

if ! command -v mountpoint > /dev/null 2>&1; then
    die "mountpoint must be present"
fi

if ! command -v findmnt > /dev/null 2>&1; then
    die "findmnt must be present"
fi

ROOT_PATH="$1"

[ -n "$ROOT_PATH" ] || die "no root given"
mountpoint -q "$ROOT_PATH" > /dev/null 2>&1 || die "root is not a mountpoint"

# make absolute and canonical once we know it exists
ROOT_PATH=$(realpath "$ROOT_PATH")

# find known pseudo-filesystems
PSEUDO_FS=$(findmnt --pseudo -Uno fstype | sort | uniq | tr '\n' ' ')

# known filesystems with fsck
FSCK_FS="cramfs exfat ext2 ext3 ext4 jfs minix msdos reiserfs vfat xfs"

is_pseudo() {
    for pfs in $PSEUDO_FS; do
        if [ "$1" = "$pfs" ]; then
            return 0
        fi
    done
    return 1
}

is_fsck() {
    for fsn in $FSCK_FS; do
        if [ "$fstype" = "$fsn" ]; then
            return 0
        fi
    done
    return 1
}

dm_name() {
    read dmn < "/sys/class/block/${1#/dev/}/dm/name"
    if [ -n "$dmn" ]; then
        echo "/dev/mapper/$dmn"
    fi
}

src_name() {
    name=
    if [ -n "$IDTAG" ]; then
        name=$(lsblk -nro $IDTAG "$1" 2>/dev/null)
    fi
    if [ -n "$name" ]; then
        echo "${IDTAG}=${name}"
    else
        echo "$1"
    fi
}

clean_opts() {
    OLD_IFS=$IFS
    IFS=,
    first=1
    for opt in $1; do
        case $opt in
            relatime) continue ;; # the default
            seclabel) continue ;; # may not be supported by target kernel
        esac
        if [ "$fstype" = "f2fs" ]; then
            # kconfig options
            case "$opt" in
                noacl|acl|nouser_xattr|user_xattr) continue ;;
            esac
        fi
        [ -n "$first" ] || printf ","
        first=
        printf "%s" "$opt"
    done
    IFS=$OLD_IFS
}

# dump the mounts for the given root
findmnt -Rcenruv -o source,target,fstype,fsroot,options "$ROOT_PATH" | \
  while read -r source target fstype fsroot options; do
    # exclude pseudo-fs early on if requested
    if [ "$INC_PSEUDOFS" -eq 0 ] && is_pseudo "$fstype"; then
        continue
    fi

    # exclude zfs, should never be in fstab
    # also filter out other filesystems that should not be here
    case "$fstype" in
        zfs|autofs|fuseblk|binfmt_misc) continue ;;
    esac

    # get real target
    if [ "$ROOT_PATH" != "/" ]; then
        if [ "$target" = "$ROOT_PATH" ]; then
            target=/
        else
            target=${target#$ROOT_PATH}
        fi
    fi

    # always exclude filesystems under /run; they are post-boot
    case "$target" in
        /run/*) continue ;;
        /) pass=1 ;;
        *) pass=2 ;;
    esac

    # set pass=0 for filesystems without fsck
    if ! is_fsck "$fstype"; then
        pass=0
    fi

    # exclude bind-mounts; hard to get right, the user can set it up manually
    if [ "$fsroot" != "/" -a "$fstype" != "btrfs" ]; then
        continue
    fi

    # clean up options
    options=$(clean_opts "$options")

    source=$(src_name "$source")
    echo "$source $target $fstype $options 0 $pass"
done

# swaps
{
    # header
    read _
    # read the lines
    while read -r dev type _ _ prio; do
        opts=defaults
        if [ "$prio" -ge 0 ]; then
            opts="$opts,pri=$prio"
        fi
        # skip deleted by the kernel
        case "$dev" in
            *"(deleted)") continue ;;
            /dev/dm-*)
                dev=$(dm_name "$dev")
                if [ -z "$dev" ]; then
                    die "could not resolve device mapper name of $dev"
                fi
                ;;
            *)
                if [ -f "$dev" ]; then
                    if [ "$ROOT_PATH" != "/" ]; then
                        dev=${dev#$ROOT_PATH}
                    fi
                fi
        esac
        dev=$(src_name "$dev")
        echo "$dev none swap $opts 0 0"
    done
} < /proc/swaps