.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}" "${df}"
  72                 fi
  73         done
  74
  75         if [[ ! -d root/.git ]] ; then
  76                 f="${HOME}/.profile.d/aliases.sh"
  77                 if [[ -e ${f} ]] ; then
  78                         cat "${f}" > root/.bash_profile
  79                 fi
  80         fi
  81 }
  82
  83 usage() {
  84         cat <<-EOF
  85         Usage: ${0##*/} [options] [program to run]
  86
  87         Sets up common mount points and then chroots in and runs a program.
  88         If no program is specified, then launch a login shell.
  89
  90         Options:
  91           -u          Unmount all paths in the chroot
  92           -m <path>   Add path to mount list
  93           -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
  94           -h          This help screen
  95         EOF
  96         exit
  97 }
  98
  99 main() {
 100         bootstrap "$@"
 101
 102         local mounts=( proc sys tmp dev dev/pts dev/shm run usr/portage usr/portage/distfiles usr/local/src )
 103
 104         local chroot=${0%/*}
 105         case ${chroot} in
 106         .) chroot=${PWD} ;;
 107         ./*) chroot=${PWD}/${chroot#./} ;;
 108         esac
 109
 110         local cmd
 111         while [[ -n $1 ]] ; do
 112                 case $1 in
 113                 -u) cmd='umount' ;;
 114                 -m) mounts+=( "$2" ); shift ;;
 115                 -d) chroot=$(realpath "$2"); shift ;;
 116                 --help|-h) usage ;;
 117                 -*) echo "${0##*/}: unknown option $1"; exit 1 ;;
 118                 *)  break ;;
 119                 esac
 120                 shift
 121         done
 122         cd "${chroot}"
 123
 124         case ${cmd} in
 125         umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
 126         esac
 127
 128         local m
 129         for m in "${mounts[@]}" ; do
 130                 maybe_mount ${m}
 131         done
 132
 133         init_chroot
 134
 135         local setarch
 136         if type -P setarch &>/dev/null ; then
 137                 local bin_dst=$(get_type bin/bash)
 138                 if [[ -n ${bin_dst} ]] ; then
 139                         setarch="setarch ${bin_dst}"
 140                 fi
 141         fi
 142
 143         # Doubtful these settings we want to leak into the chroot.
 144         unset ROOT PORTAGE_CONFIGROOT LD_LIBRARY_PATH
 145         unset LS_COLORS # format changes over time
 146         [[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
 147         exec \
 148                 ${setarch} \
 149                 chroot "${chroot}" \
 150                 "$@"
 151 }
 152
 153 main "$@"