.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 ${UNSHARE} ]] ; then
   7                 mount_args=
   8                 if type -P unshare >&/dev/null ; then
   9                         test_arg() { unshare "$@" -- true >&/dev/null && uargs+=( "$@" ) || :; }
  10                         uargs=( -m )
  11                         test_arg -u
  12                         test_arg -i
  13                         test_arg -p -f --mount-proc
  14                         test_arg --propagation=private
  15                         UNSHARE=true exec unshare "${uargs[@]}" -- "$0" "$@"
  16                 fi
  17         else
  18                 mount_args='-n'
  19         fi
  20         unset UNSHARE
  21 }
  22
  23 maybe_mount() {
  24         local src=/$1 dst=${chroot}/${2:-$1}
  25         [[ -d ${src} ]] || return 0
  26         if ! mkdir -p "${dst}" ; then
  27                 [[ -w ${chroot} ]] && exit 1 || return 0
  28         fi
  29         grep -sq "${dst}" /proc/mounts || mount ${mount_args} --bind "${src}" "${dst}"
  30 }
  31
  32 get_type() {
  33         case $(file "$1") in
  34         *x86-64*)         echo x86_64;;
  35         *"Intel 80386"*)  echo i386;;
  36         *32-bit*PowerPC*) echo ppc;;
  37         *64-bit*PowerPC*) echo ppc64;;
  38         *32-bit*S/390*)   echo s390;;
  39         *64-bit*S/390*)   echo s390x;;
  40         *64-bit*MIPS*)    echo mips64;;
  41         *32-bit*MIPS*N32*)echo mips64;;
  42         *32-bit*MIPS*)    echo mips;;
  43         *32-bit*PA-RISC*) echo parisc;;
  44         *64-bit*PA-RISC*) echo parisc64;;
  45         *32-bit*SPARC*)   echo sparc;;
  46         *64-bit*SPARC*)   echo sparc64;;
  47         esac
  48 }
  49
  50 init_chroot() {
  51         [[ -w . ]] || return 0
  52
  53         if [[ ! -L etc/mtab ]] ; then
  54                 ln -sfT /proc/mounts etc/mtab
  55         fi
  56         local f dst
  57         local etc=(
  58                 hosts
  59                 locale.gen
  60                 localtime
  61                 resolv.conf
  62         )
  63         local home=(
  64                 .inputrc
  65                 .gdbinit
  66                 .gitconfig
  67                 .nanorc
  68         )
  69         for f in \
  70                 $(printf 'etc/%s ' "${etc[@]}") \
  71         ; do
  72                 if [[ -e /${f} ]] ; then
  73                         cp "/${f}" "${f}"
  74                 fi
  75         done
  76         for f in "${home[@]}" ; do
  77                 df="root/${f}"
  78                 f="${HOME}/${f}"
  79                 if [[ -e ${f} ]] ; then
  80                         cp "${f}" "${df}"
  81                 fi
  82         done
  83
  84         if [[ ! -d root/.git ]] ; then
  85                 f="${HOME}/.profile.d/aliases.sh"
  86                 if [[ -e ${f} ]] ; then
  87                         cat "${f}" > root/.bash_profile
  88                 fi
  89         fi
  90 }
  91
  92 usage() {
  93         cat <<-EOF
  94         Usage: ${0##*/} [options] [program to run]
  95
  96         Sets up common mount points and then chroots in and runs a program.
  97         If no program is specified, then launch a login shell.
  98
  99         Options:
 100           -u          Unmount all paths in the chroot
 101           -m <path>   Add path to mount list
 102           -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
 103           -h          This help screen
 104         EOF
 105         exit
 106 }
 107
 108 main() {
 109         bootstrap "$@"
 110
 111         local mounts=( proc sys tmp dev dev/pts dev/shm run usr/portage usr/portage/distfiles usr/local/src )
 112
 113         local chroot=${0%/*}
 114         case ${chroot} in
 115         .) chroot=${PWD} ;;
 116         ./*) chroot=${PWD}/${chroot#./} ;;
 117         esac
 118
 119         local cmd
 120         while [[ -n $1 ]] ; do
 121                 case $1 in
 122                 -u) cmd='umount' ;;
 123                 -m) mounts+=( "$2" ); shift ;;
 124                 -d) chroot=$(realpath "$2"); shift ;;
 125                 --help|-h) usage ;;
 126                 -*) echo "${0##*/}: unknown option $1"; exit 1 ;;
 127                 *)  break ;;
 128                 esac
 129                 shift
 130         done
 131         cd "${chroot}"
 132
 133         case ${cmd} in
 134         umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
 135         esac
 136
 137         local m
 138         for m in "${mounts[@]}" ; do
 139                 maybe_mount ${m}
 140         done
 141
 142         init_chroot
 143
 144         local setarch
 145         if type -P setarch &>/dev/null ; then
 146                 local bin_dst=$(get_type bin/bash)
 147                 if [[ -n ${bin_dst} ]] ; then
 148                         setarch="setarch ${bin_dst}"
 149                 fi
 150         fi
 151
 152         # Doubtful these settings we want to leak into the chroot.
 153         unset ROOT PORTAGE_CONFIGROOT LD_LIBRARY_PATH
 154         unset LS_COLORS # format changes over time
 155         [[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
 156         exec \
 157                 ${setarch} \
 158                 chroot "${chroot}" \
 159                 "$@"
 160 }
 161
 162 main "$@"