.bin/custom-chroot

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