[X2go-dev] Suggestion: Make x2gothinclientsystem less invasive

Hi x2go folks,

I would like to suggest a solution to make x2gothinclientsystem less invasive.

Instead of mounting a ramdisk and removing/symlinking some files and directories (which might be a Debian packaging policy violation) it might be smarter to mount a read only root filesystem and transparently overlay it with a tempfs.

I can this be achieved?

a) Install aufs modules in the clients' chroot environment. Aufs modules are part of Squeeze's default kernel.

b) Add "aufs" to /etc/initramfs-tools/modules.

c) Set "BOOT=aufs" in /etc/initramfs-tools/initramfs.conf.

d) Add a "magic" script (see attachment) named "aufs" to /etc/initramfs-tools/scripts

e) Call update-initramfs -u inside the chroot.

The "aufs" script is based on Debian's /usr/share/initramfs-tools/scripts/nfs script.

The attached script provides a three layer file root filesystem.

ro nfsroot/master (generic thinclients' chroot) ro nfsroot/<ip-address> (individual thinclient's configuration overriding master) rw tempfs (simulates a fully rw root file system)

Pros:

• simple (to my mind)
• flexible
• less "hacky" (less/no conflicts with other packages)
• therefore more Debian compliant (to my mind)
• x2go related stuff currently stored in /ramdisk can go into /var/lib/x2go...

Cons:

• any?

Any feedback is appreciated.

Michael

-- EDV-Serviceteam Annika & Michael Hierweck GbR Egerstraße 53, 44225 Dortmund (Germany) http://www.edv-serviceteam.net

# NFS filesystem mounting -*- shell-script -*-

# FIXME This needs error checking

retry_nr=0

# parse nfs bootargs and mount nfs do_nfsmount() {

configure_networking

# get nfs root from dhcp
if [ "x${NFSROOT}" = "xauto" ]; then
	# check if server ip is part of dhcp root-path
	if [ "${ROOTPATH#*:}" = "${ROOTPATH}" ]; then
		NFSROOT=${ROOTSERVER}:${ROOTPATH}
	else
		NFSROOT=${ROOTPATH}
	fi

# nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
elif [ -n "${NFSROOT}" ]; then
	# nfs options are an optional arg
	if [ "${NFSROOT#*,}" != "${NFSROOT}" ]; then
		NFSOPTS="-o ${NFSROOT#*,}"
	fi
	NFSROOT=${NFSROOT%%,*}
	if [ "${NFSROOT#*:}" = "$NFSROOT" ]; then
		NFSROOT=${ROOTSERVER}:${NFSROOT}
	fi
fi

if [ -z "${NFSOPTS}" ]; then
	NFSOPTS="-o retrans=10"
fi

[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/nfs-premount"
run_scripts /scripts/nfs-premount
[ "$quiet" != "y" ] && log_end_msg

if [ ${readonly} = y ]; then
	roflag="-o ro"
else
	roflag="-o rw"
fi

mkdir -p /aufs-root
mkdir -p /aufs-conf
mkdir -p /aufs-temp

nfsmount -o nolock ${roflag} ${NFSOPTS} ${NFSROOT}/master /aufs-root
nfsmount -o nolock ${roflag} ${NFSOPTS} ${NFSROOT}/config/${IPV4ADDR} /aufs-conf

mount -t tmpfs tmpfs /aufs-temp

mount -t aufs -o dirs=/aufs-temp=rw:/aufs-conf=ro:/aufs-root=ro aufs ${rootmnt}

}

# NFS root mounting mountroot() { [ "$quiet" != "y" ] && log_begin_msg "Running /scripts/nfs-top" run_scripts /scripts/nfs-top [ "$quiet" != "y" ] && log_end_msg

modprobe nfs
# For DHCP
modprobe af_packet

wait_for_udev 10

# Default delay is around 180s
# FIXME: add usplash_write info
if [ -z "${ROOTDELAY}" ]; then
	delay=180
else
	delay=${ROOTDELAY}
fi

# loop until nfsmount succeds
while [ ${retry_nr} -lt ${delay} ] && [ ! -e ${rootmnt}${init} ]; do
	[ ${retry_nr} -gt 0 ] && \
	[ "$quiet" != "y" ] && log_begin_msg "Retrying nfs mount"
	do_nfsmount
	retry_nr=$(( ${retry_nr} + 1 ))
	[ ! -e ${rootmnt}${init} ] && /bin/sleep 1
	[ ${retry_nr} -gt 0 ] && [ "$quiet" != "y" ] && log_end_msg
done

[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/nfs-bottom"
run_scripts /scripts/nfs-bottom
[ "$quiet" != "y" ] && log_end_msg

}