.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 is_mounted() {
  24         local dst=$1
  25         grep -sq "${dst}" /proc/mounts
  26 }
  27
  28 maybe_mount() {
  29         local src=/$1 dst=${chroot}/${2:-$1}
  30         [[ -d ${src} ]] || return 0
  31         if ! mkdir -p "${dst}" ; then
  32                 [[ -w ${chroot} ]] && exit 1 || return 0
  33         fi
  34         is_mounted "${dst}" || mount ${mount_args} --bind "${src}" "${dst}"
  35 }
  36
  37 get_type() {
  38         case $(file "$1") in
  39         *x86-64*)         echo x86_64;;
  40         *"Intel 80386"*)  echo i386;;
  41         *32-bit*PowerPC*) echo ppc;;
  42         *64-bit*PowerPC*) echo ppc64;;
  43         *32-bit*S/390*)   echo s390;;
  44         *64-bit*S/390*)   echo s390x;;
  45         *64-bit*MIPS*)    echo mips64;;
  46         *32-bit*MIPS*N32*)echo mips64;;
  47         *32-bit*MIPS*)    echo mips;;
  48         *32-bit*PA-RISC*) echo parisc;;
  49         *64-bit*PA-RISC*) echo parisc64;;
  50         *32-bit*SPARC*)   echo sparc;;
  51         *64-bit*SPARC*)   echo sparc64;;
  52         esac
  53 }
  54
  55 init_chroot() {
  56         [[ -w . ]] || return 0
  57
  58         if [[ ! -L etc/mtab ]] ; then
  59                 ln -sfT /proc/mounts etc/mtab
  60         fi
  61         local f dst
  62         local etc=(
  63                 hosts
  64                 locale.gen
  65                 localtime
  66                 resolv.conf
  67         )
  68         local home=(
  69                 .inputrc
  70                 .gdbinit
  71                 .gitconfig
  72                 .nanorc
  73         )
  74         for f in \
  75                 $(printf 'etc/%s ' "${etc[@]}") \
  76         ; do
  77                 if [[ -e /${f} ]] ; then
  78                         cp "/${f}" "${f}"
  79                 fi
  80         done
  81         for f in "${home[@]}" ; do
  82                 df="root/${f}"
  83                 f="${HOME}/${f}"
  84                 if [[ -e ${f} ]] ; then
  85                         cp "${f}" "${df}"
  86                 fi
  87         done
  88
  89         if [[ ! -d root/.git ]] ; then
  90                 f="${HOME}/.profile.d/aliases.sh"
  91                 if [[ -e ${f} ]] ; then
  92                         cat "${f}" > root/.bash_profile
  93                 fi
  94         fi
  95 }
  96
  97 usage() {
  98         cat <<-EOF
  99         Usage: ${0##*/} [options] [program to run]
 100
 101         Sets up common mount points and then chroots in and runs a program.
 102         If no program is specified, then launch a login shell.
 103
 104         Options:
 105           -u          Unmount all paths in the chroot
 106           -m <path>   Add path to mount list
 107           -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
 108           -h          This help screen
 109         EOF
 110         exit
 111 }
 112
 113 main() {
 114         bootstrap "$@"
 115
 116         local mounts=( proc sys tmp dev dev/shm run usr/portage usr/portage/distfiles usr/local/src )
 117
 118         local chroot=${0%/*}
 119         case ${chroot} in
 120         .) chroot=${PWD} ;;
 121         ./*) chroot=${PWD}/${chroot#./} ;;
 122         esac
 123
 124         local cmd
 125         while [[ -n $1 ]] ; do
 126                 case $1 in
 127                 -u) cmd='umount' ;;
 128                 -m) mounts+=( "$2" ); shift ;;
 129                 -d) chroot=$(realpath "$2"); shift ;;
 130                 --help|-h) usage ;;
 131                 -*) echo "${0##*/}: unknown option $1"; exit 1 ;;
 132                 *)  break ;;
 133                 esac
 134                 shift
 135         done
 136         cd "${chroot}"
 137
 138         case ${cmd} in
 139         umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
 140         esac
 141
 142         local m
 143         for m in "${mounts[@]}" ; do
 144                 maybe_mount "${m}"
 145         done
 146         # Handle special mounts that we don't want to just bind mount.
 147         if ! is_mounted "${chroot}/dev/pts" ; then
 148                 mount -t devpts devpts "${chroot}/dev/pts" \
 149                         -o nosuid,noexec,newinstance,ptmxmode=0666,mode=0620,gid=5
 150         fi
 151
 152         init_chroot
 153
 154         local setarch
 155         if type -P setarch &>/dev/null ; then
 156                 local bin_dst=$(get_type bin/bash)
 157                 if [[ -n ${bin_dst} ]] ; then
 158                         setarch="setarch ${bin_dst}"
 159                 fi
 160         fi
 161
 162         # Doubtful these settings we want to leak into the chroot.
 163         unset ROOT PORTAGE_CONFIGROOT LD_LIBRARY_PATH
 164         unset LS_COLORS # format changes over time
 165         [[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
 166         exec \
 167                 ${setarch} \
 168                 chroot "${chroot}" \
 169                 "$@"
 170 }
 171
 172 main "$@"