.bin/custom-chroot

   1 #!/bin/bash -e
   2
   3 bootstrap() {
   4         [[ $(id -u) -eq 0 ]] || exec sudo env -uUNSHARE HOME="$HOME" "$0" "$@"
   5
   6         if [[ -z ${UNSHARE} ]] ; then
   7                 mount_args=
   8                 if type -P unshare >&/dev/null ; then
   9                         uargs=( -m )
  10                         unshare -u -- true >&/dev/null && uargs+=( -u )
  11                         unshare -i -- true >&/dev/null && uargs+=( -i )
  12                         unshare -p -- true >&/dev/null && uargs+=( -p -f --mount-proc )
  13                         UNSHARE=true exec unshare "${uargs[@]}" -- "$0" "$@"
  14                 fi
  15         else
  16                 mount_args='-n'
  17         fi
  18         unset UNSHARE
  19 }
  20
  21 maybe_mount() {
  22         local src=/$1 dst=${chroot}/${2:-$1}
  23         [[ -d ${src} ]] || return 0
  24         if ! mkdir -p "${dst}" ; then
  25                 [[ -w ${chroot} ]] && exit 1 || return 0
  26         fi
  27         grep -sq "${dst}" /proc/mounts || mount ${mount_args} --bind "${src}" "${dst}"
  28 }
  29
  30 get_type() {
  31         case $(file "$1") in
  32         *x86-64*)         echo x86_64;;
  33         *"Intel 80386"*)  echo i386;;
  34         *32-bit*PowerPC*) echo ppc;;
  35         *64-bit*PowerPC*) echo ppc64;;
  36         *32-bit*S/390*)   echo s390;;
  37         *64-bit*S/390*)   echo s390x;;
  38         esac
  39 }
  40
  41 init_chroot() {
  42         [[ -w . ]] || return 0
  43
  44         if [[ ! -L etc/mtab ]] ; then
  45                 ln -sfT /proc/mounts etc/mtab
  46         fi
  47         local f dst
  48         local etc=(
  49                 hosts
  50                 locale.gen
  51                 localtime
  52                 resolv.conf
  53         )
  54         local home=(
  55                 .inputrc
  56                 .gdbinit
  57                 .gitconfig
  58                 .nanorc
  59         )
  60         for f in \
  61                 $(printf 'etc/%s ' "${etc[@]}") \
  62         ; do
  63                 if [[ -e /${f} ]] ; then
  64                         cp "/${f}" "${f}"
  65                 fi
  66         done
  67         for f in "${home[@]}" ; do
  68                 df="root/${f}"
  69                 f="${HOME}/${f}"
  70                 if [[ -e ${f} ]] ; then
  71                         cp "${f}" "${df}"
  72                 fi
  73         done
  74
  75         f="${HOME}/.profile.d/aliases.sh"
  76         if [[ -e ${f} ]] ; then
  77                 cat "${f}" > root/.bash_profile
  78         fi
  79 }
  80
  81 usage() {
  82         cat <<-EOF
  83         Usage: ${0##*/} [options] [program to run]
  84
  85         Sets up common mount points and then chroots in and runs a program.
  86         If no program is specified, then launch a login shell.
  87
  88         Options:
  89           -u          Unmount all paths in the chroot
  90           -m <path>   Add path to mount list
  91           -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
  92           -h          This help screen
  93         EOF
  94         exit
  95 }
  96
  97 main() {
  98         bootstrap "$@"
  99
 100         local mounts=( proc sys tmp dev dev/pts dev/shm run usr/portage usr/portage/distfiles usr/local/src )
 101
 102         local chroot=${0%/*}
 103         case ${chroot} in
 104         .) chroot=${PWD} ;;
 105         ./*) chroot=${PWD}/${chroot#./} ;;
 106         esac
 107
 108         local cmd
 109         while [[ -n $1 ]] ; do
 110                 case $1 in
 111                 -u) cmd='umount' ;;
 112                 -m) mounts+=( "$2" ); shift ;;
 113                 -d) chroot=$(realpath "$2"); shift ;;
 114                 --help|-h) usage ;;
 115                 -*) echo "${0##*/}: unknown option $1"; exit 1 ;;
 116                 *)  break ;;
 117                 esac
 118                 shift
 119         done
 120         cd "${chroot}"
 121
 122         case ${cmd} in
 123         umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
 124         esac
 125
 126         local m
 127         for m in "${mounts[@]}" ; do
 128                 maybe_mount ${m}
 129         done
 130
 131         init_chroot
 132
 133         local setarch
 134         if type -P setarch &>/dev/null ; then
 135                 local bin_dst=$(get_type bin/bash)
 136                 if [[ -n ${bin_dst} ]] ; then
 137                         setarch="setarch ${bin_dst}"
 138                 fi
 139         fi
 140
 141         # Doubtful these settings we want to leak into the chroot.
 142         unset ROOT PORTAGE_CONFIGROOT LD_LIBRARY_PATH
 143         unset LS_COLORS # format changes over time
 144         [[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
 145         exec \
 146                 ${setarch} \
 147                 chroot "${chroot}" \
 148                 "$@"
 149 }
 150
 151 main "$@"