.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                         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                 ln -sfT /proc/mounts etc/mtab
  42         fi
  43         local f dst
  44         local etc=(
  45                 hosts
  46                 locale.gen
  47                 localtime
  48                 resolv.conf
  49         )
  50         local home=(
  51                 .inputrc
  52                 .gdbinit
  53                 .gitconfig
  54                 .nanorc
  55         )
  56         for f in \
  57                 $(printf 'etc/%s ' "${etc[@]}") \
  58         ; do
  59                 if [[ -e /${f} ]] ; then
  60                         cp "/${f}" "${f}"
  61                 fi
  62         done
  63         for f in "${home[@]}" ; do
  64                 df="root/${f}"
  65                 f="${HOME}/${f}"
  66                 if [[ -e ${f} ]] ; then
  67                         cp "${f}" "${df}"
  68                 fi
  69         done
  70
  71         f="${HOME}/.profile.d/aliases.sh"
  72         if [[ -e ${f} ]] ; then
  73                 cat "${f}" > root/.bash_profile
  74         fi
  75 }
  76
  77 usage() {
  78         cat <<-EOF
  79         Usage: ${0##*/} [options] [program to run]
  80
  81         Sets up common mount points and then chroots in and runs a program.
  82         If no program is specified, then launch a login shell.
  83
  84         Options:
  85           -u          Unmount all paths in the chroot
  86           -m <path>   Add path to mount list
  87           -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
  88           -h          This help screen
  89         EOF
  90         exit
  91 }
  92
  93 main() {
  94         bootstrap "$@"
  95
  96         local mounts=( proc sys tmp dev dev/pts dev/shm usr/portage usr/portage/distfiles usr/local/src )
  97
  98         local chroot=${0%/*}
  99         case ${chroot} in
 100         .) chroot=${PWD} ;;
 101         ./*) chroot=${PWD}/${chroot#./} ;;
 102         esac
 103
 104         local cmd
 105         while [[ -n $1 ]] ; do
 106                 case $1 in
 107                 -u) cmd='umount' ;;
 108                 -m) mounts+=( "$2" ); shift ;;
 109                 -d) chroot=$(realpath "$2"); shift ;;
 110                 -h) usage ;;
 111                 -*) echo "${0##*/}: unknown option $1"; exit 1 ;;
 112                 *)  break ;;
 113                 esac
 114                 shift
 115         done
 116         cd "${chroot}"
 117
 118         case ${cmd} in
 119         umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
 120         esac
 121
 122         local m
 123         for m in "${mounts[@]}" ; do
 124                 maybe_mount ${m}
 125         done
 126
 127         init_chroot
 128
 129         local setarch
 130         if type -P setarch &>/dev/null ; then
 131                 local bin_dst=$(get_type bin/bash)
 132                 if [[ -n ${bin_dst} ]] ; then
 133                         setarch="setarch ${bin_dst}"
 134                 fi
 135         fi
 136
 137         unset LS_COLORS # format changes over time
 138         [[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
 139         exec \
 140                 ${setarch} \
 141                 chroot "${chroot}" \
 142                 "$@"
 143 }
 144
 145 main "$@"