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Planning for LTSP EPEL-6



Hi folks,

Joshua Trimm (FAS: enslaver) has joined the K12Linux project, and is currently working on formal integration of LTSP for EL-6.  It is our intent for EPEL-6 to eventually contain all components of LTSP.  After EPEL-6 is complete, Fedora may be considered.  I have largely moved on from this project, but I am helping the transition to new developers.  Joshua is doing at least EPEL-6 since his employer relies upon it.  In the long-term K12Linux needs more knowledgeable Fedora developers in order to be sustainable.

Packages
Certain: ltsp, ltspfs, ldm, mkdst, nbd, ltsp-client-kernel
Possibly: unionfs-fuse

NBD needs to be upgraded in EPEL-6
https://bugzilla.redhat.com/show_bug.cgi?id=695066#c3 
Prior versions of NBD lacked initscripts and standard port assignments, but this has changed with recent versions of NBD upstream.

https://bugzilla.redhat.com/show_bug.cgi?id=877518
A systemd unit file was proposed here.  We would need an equivalent sysvinit script for EPEL-6.

NBD Upgrade Risk Analysis
I believe we have a strong case for upgrading under any of the above scenarios.  Joshua will research the compatibility issue to better inform us of the actual extent of upgrade risk.

unionfs-fuse and dracut module
Currently LTSP clients netboot a dracut-network generated initrd which mounts a read-only NFS or NBD root filesystem and relies upon /etc/rwtab*.  In theory rwtab bind mounts copies of files and directories to the read-only filesystem to allow a stateless client to boot.  In practice rwtab has significant problems and was never well supported as most developers never test in readonly root stateless mode.  As an alternative, Joshua intends to try the fuse-based unionfs overlay to mimic the kernel-based unionfs overlay used by Debian LTSP.

http://podgorny.cz/moin/UnionFsFuse
http://pkgs.repoforge.org/fuse-unionfs/
Someone made packages, although it hasn't been tried yet.  It would theoretically require a dracut module to move /sysroot to another name, then mount the fuse overlay as /sysroot prior to mounting of any auxiliary filesystems (/proc?) and switch_root.  The "other name" may need to be protected from the deletion that occurs prior to switch_root.  Hopefully fuse will work as expected even after a switch_root.

LTSP Client Kernel
https://www.redhat.com/archives/epel-devel-list/2011-May/msg00059.html
LTSP for EPEL-6 will require a LTSP-only embedded kernel as proposed back in May 2011.  Please see this previous thread about why it would be safe for EPEL-6.

Warren Togami

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