From a7491e13497b24d20517535ae7c767c7f32c40a1 Mon Sep 17 00:00:00 2001
From: Jesse Hathaway <jesse@mbuki-mvuki.org>
Date: Tue, 23 Oct 2007 16:56:43 -0400
Subject: add exposedroot option which exposes the root fs as ro

This option allows you to expose the root read only.  Using
this option a person could upgrade the root filesystem or
add packages without requiring the user to reboot. The root
filesystem could be kept on an nfs volume or some other
persistent medium. Multiple clients could then be booted off
the same root fs. I used LTSP as a template to determine which
directories to make rw.
---
 helpers/lh_chroot_hacks | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

(limited to 'helpers/lh_chroot_hacks')

diff --git a/helpers/lh_chroot_hacks b/helpers/lh_chroot_hacks
index da2be1723..6eaef4f04 100755
--- a/helpers/lh_chroot_hacks
+++ b/helpers/lh_chroot_hacks
@@ -111,5 +111,44 @@ then
 	chown -R --quiet 999:999 chroot/home/${LH_USERNAME}
 fi
 
+if [ "${LH_EXPOSED_ROOT}" = "enabled" ]
+then
+	# Make sure RW dirs exist so that the initramfs script has
+	# a directory in which to bind the tmpfs filesystems
+	COW_DIRS='/tmp /var/tmp /var/lock /var/run /var/lib/live /var/log
+		/var/spool /home /live'
+	for DIR in ${COW_DIRS}; do
+		mkdir -p chroot${DIR}
+	done
+
+	# Config files which need to be RW
+	CONFIG_FILES='/etc/hostname /etc/hosts /etc/resolv.conf /etc/fstab
+		/etc/live.conf /etc/network/interfaces /etc/X11/xorg.conf
+		/etc/udev/rules.d/z25_persistent-net.rules
+		/etc/udev/rules.d/z25_persistent-cd.rules'
+
+	# Where we will store RW config files
+	RW_DIR='/var/lib/live'
+
+	for FILE_PATH in ${CONFIG_FILES}
+	do
+		# Touch files in case they don't yet exist
+		FILE_DIR=$(dirname ${FILE_PATH})
+		mkdir -p chroot${FILE_DIR}
+		touch chroot${FILE_PATH}
+		FILE_NAME=$(basename ${FILE_PATH})
+		mkdir -p chroot${RW_DIR}${FILE_DIR}
+		mv chroot${FILE_PATH} chroot${RW_DIR}${FILE_DIR}
+		# Create a symbolic link to RW config file
+		RELATIVE_PATH=$(echo ${FILE_DIR}|sed 's/[^\/]\+/../g; s/^\///g')
+		ln -s ${RELATIVE_PATH}${RW_DIR}${FILE_PATH} chroot${FILE_PATH}
+	done
+
+	# Mount doesn't write to a symlink so use /proc/mounts instead,
+	# see debian bug #154438 for more info
+	rm chroot/etc/mtab
+	ln -s /proc/mounts chroot/etc/mtab
+fi
+
 # Creating stage file
 Create_stagefile .stage/chroot_hacks
-- 
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