1#!/bin/sh
 2# Enter a kiss chroot
 3
 4log() {
 5    printf '\033[32m->\033[m %s.\n' "$*"
 6}
 7
 8die() {
 9    log "$*" >&2
10    exit 1
11}
12
13run() {
14    printf '%s\n' "$*"
15    "$@" || return "${_ret:=0}"
16}
17
18clean() {
19    {
20        run umount "$1/dev/shm" 2>/dev/null
21        run umount "$1/dev/pts"
22        run umount "$1/dev"
23        run umount "$1/proc"
24        run umount "$1/run"
25        run umount "$1/sys/firmware/efi/efivars" 2>/dev/null
26        run umount "$1/sys"
27        run umount "$1/tmp"
28        run umount "$1/etc/resolv.conf"
29    }
30}
31
32mounted() {
33    # This is a pure shell mountpoint implementation. We're dealing
34    # with basic (and fixed/known) input so this doesn't need to
35    # handle more complex cases.
36    [ -e "$1" ]         || return 1
37    [ -e /proc/mounts ] || return 1
38
39    while read -r _ target _; do
40        [ "$target" = "$1" ] && return 0
41    done < /proc/mounts
42
43    return 1
44}
45
46mmount() {
47    dest=$1
48    shift
49    mounted "$dest" || run mount "$@" "$dest"
50}
51
52main() {
53    # Ensure input does not end in '/'.
54    set -- "${1%"${1##*[!/]}"}"
55
56    [ "$1" ]           || die Need a path to the chroot
57    [ -d "$1" ]        || die Given path does not exist
58    [ "$(id -u)" = 0 ] || die Script needs to be run as root
59
60    # Intended behaviour.
61    # shellcheck disable=SC2064
62    #trap "clean ${1%"${1##*[!/]}"}" EXIT INT
63
64    {
65        mmount "$1/dev"     -o bind /dev
66        mmount "$1/dev/pts" -o bind /dev/pts
67        mmount "$1/dev/shm" -t tmpfs shmfs 2>/dev/null
68        mmount "$1/proc"    -t proc  proc
69        mmount "$1/run"     -t tmpfs tmpfs
70        mmount "$1/sys"     -t sysfs sys
71        mmount "$1/sys/firmware/efi/efivars" -t efivarfs efivarfs 2>/dev/null
72        mmount "$1/tmp"     -o mode=1777,nosuid,nodev -t tmpfs tmpfs
73
74        touch  "$1/etc/resolv.conf"
75        mmount "$1/etc/resolv.conf" -o bind /etc/resolv.conf
76    }
77
78}
79
80# unmount if 2nd arg passed
81[ $2 ] && { clean ${1%"${1##*[!/]}"}; exit 0; }
82main "$1"