From: Mike Frysinger <vapier@gentoo.org>
Date: Sun, 7 Apr 2013 21:40:44 +0000 (-0400)
Subject: custom-chroot: overhaul to clean up and add read-only chroot support
X-Git-Url: https://git.wh0rd.org/?a=commitdiff_plain;h=35fd42a7cb626bb70a33b3b1250e2006bdf518d9;p=home.git

custom-chroot: overhaul to clean up and add read-only chroot support
---

diff --git a/.bin/custom-chroot b/.bin/custom-chroot
index 878a8ff..a32a75f 100755
--- a/.bin/custom-chroot
+++ b/.bin/custom-chroot
@@ -1,102 +1,137 @@
 #!/bin/bash -e
 
-[[ -w / ]] || exec sudo env HOME="$HOME" "$0" "$@"
+bootstrap() {
+	[[ -w / ]] || exec sudo env -uUNSHARE HOME="$HOME" "$0" "$@"
 
-if [[ -z ${UNSHARE} ]] ; then
-	mount_args=
-	if type -P unshare >&/dev/null ; then
-		UNSHARE=true exec unshare -m -- "$0" "$@"
+	if [[ -z ${UNSHARE} ]] ; then
+		mount_args=
+		if type -P unshare >&/dev/null ; then
+			UNSHARE=true exec unshare -m -- "$0" "$@"
+		fi
+	else
+		mount_args='-n'
 	fi
-else
-	mount_args='-n'
-fi
-unset UNSHARE
-
-mounts="proc sys tmp dev dev/pts usr/portage usr/portage/distfiles usr/local/src"
-
-chroot=${0%/*}
-case ${chroot} in
-	.) chroot=${PWD} ;;
-	./*) chroot=${PWD}/${chroot#./} ;;
-esac
-cd "${chroot}"
-
-do_umount() {
-	local m mounts=$(mount | grep ${chroot} | awk '{print $3}' | tac)
-	for m in ${mounts} ; do
-		echo "unmounting ${m}"
-		umount "${m}"
-	done
-	if [[ -z ${mounts} ]] ; then
-		echo "nothing mounted in ${chroot}"
-	fi
-	exit 0
+	unset UNSHARE
 }
 
-while [[ -n $1 ]] ; do
-	case $1 in
-	-u) do_umount ;;
-	-m) mounts+=" $2"; shift ;;
-	-*) echo "unknown option $1"; exit 1 ;;
-	*)  break ;;
-	esac
-	shift
-done
-
 maybe_mount() {
 	local src=/$1 dst=${chroot}/${2:-$1}
 	[[ -d ${src} ]] || return 0
-	mkdir -p "${dst}"
+	if ! mkdir -p "${dst}" ; then
+		[[ -w ${chroot} ]] && exit 1 || return 0
+	fi
 	grep -sq "${dst}" /proc/mounts || mount ${mount_args} --bind "${src}" "${dst}"
 }
-for m in ${mounts} ; do
-	maybe_mount ${m}
-done
 
 get_type() {
 	case $(file "$1") in
-		*x86-64*)         echo x86_64;;
-		*"Intel 80386"*)  echo i386;;
-		*32-bit*PowerPC*) echo ppc;;
-		*64-bit*PowerPC*) echo ppc64;;
+	*x86-64*)         echo x86_64;;
+	*"Intel 80386"*)  echo i386;;
+	*32-bit*PowerPC*) echo ppc;;
+	*64-bit*PowerPC*) echo ppc64;;
+	*32-bit*S/390*)   echo s390;;
+	*64-bit*S/390*)   echo s390x;;
 	esac
 }
-bin_dst=$(get_type bin/bash)
-setarch=
-if [[ -n ${bin_dst} ]] && type -P setarch &>/dev/null ; then
-	setarch="setarch ${bin_dst}"
-fi
-
-if [[ ! -L etc/mtab ]] ; then
-	rm -f etc/mtab
-	ln -sf /proc/mounts etc/mtab
-fi
-etc="
-	hosts
-	locale.gen
-	localtime
-	resolv.conf
-"
-home="
-	.inputrc
-	.gdbinit
-	.gitconfig
-	.nanorc
-"
-for f in \
-	$(printf 'etc/%s ' ${etc}) \
-; do
-	if [ -e "/${f}" ] ; then
-		cp /${f} ${f}
+
+init_chroot() {
+	[[ -w . ]] || return 0
+
+	if [[ ! -L etc/mtab ]] ; then
+		rm -f etc/mtab
+		ln -sf /proc/mounts etc/mtab
+	fi
+	local f
+	local etc=(
+		hosts
+		locale.gen
+		localtime
+		resolv.conf
+	)
+	local home=(
+		.inputrc
+		.gdbinit
+		.gitconfig
+		.nanorc
+	)
+	for f in \
+		$(printf 'etc/%s ' "${etc[@]}") \
+	; do
+		if [ -e "/${f}" ] ; then
+			cp /${f} ${f}
+		fi
+	done
+	for f in "${home[@]}" ; do
+		cp "${HOME}/${f}" "root/${f}"
+	done
+}
+
+usage() {
+	cat <<-EOF
+	Usage: ${0##*/} [options] [program to run]
+
+	Sets up common mount points and then chroots in and runs a program.
+	If no program is specified, then launch a login shell.
+
+	Options:
+	  -u          Unmount all paths in the chroot
+	  -m <path>   Add path to mount list
+	  -d <dir>    Use <dir> as chroot (defaults to ${0%/*})
+	  -h          This help screen
+	EOF
+	exit
+}
+
+main() {
+	bootstrap "$@"
+
+	local mounts=( proc sys tmp dev dev/pts usr/portage usr/portage/distfiles usr/local/src )
+
+	local chroot=${0%/*}
+	case ${chroot} in
+	.) chroot=${PWD} ;;
+	./*) chroot=${PWD}/${chroot#./} ;;
+	esac
+
+	local cmd
+	while [[ -n $1 ]] ; do
+		case $1 in
+		-u) cmd='umount' ;;
+		-m) mounts+=( "$2" ); shift ;;
+		-d) chroot=$(realpath "$2"); shift ;;
+		-h) usage ;;
+		-*) echo "${0##*/}: unknown option $1"; exit 1 ;;
+		*)  break ;;
+		esac
+		shift
+	done
+	cd "${chroot}"
+
+	case ${cmd} in
+	umount) exec "${0%/*}/umount-tree" -y "${chroot}" ;;
+	esac
+
+	local m
+	for m in "${mounts[@]}" ; do
+		maybe_mount ${m}
+	done
+
+	init_chroot
+
+	local setarch
+	if type -P setarch &>/dev/null ; then
+		local bin_dst=$(get_type bin/bash)
+		if [[ -n ${bin_dst} ]] ; then
+			setarch="setarch ${bin_dst}"
+		fi
 	fi
-done
-for f in ${home} ; do
-	cp ~/${f} root/${f}
-done
-
-unset LS_COLORS # format changes over time
-[[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
-exec \
-	${setarch} \
-	chroot "${chroot}" \
-	"$@"
+
+	unset LS_COLORS # format changes over time
+	[[ $# -eq 0 ]] && set -- env HOME=/root /bin/bash -l
+	exec \
+		${setarch} \
+		chroot "${chroot}" \
+		"$@"
+}
+
+main "$@"