[mythtv-users] Best options/howto for diskless frontends

[Raymond Wagner]

On 10/24/2012 15:46, Michael Drons wrote:
> My only requirement is that the frontends boot quickly.  The gentoo FE
> boot from power on to mythtv ready in about 45 seconds with no
> hibernation or sleep configured.
>
> A nice to have would be for the frontends to share the nfs partition
> (currently have 3 diskless fe).  My current setup takes a lot of disk as
> each FE has its own root nfs mount point.

I have a fairly unorthodox configuration. I have all my frontends 
booting Gentoo over iSCSI. The backing store are volumes stored on ZFS 
on my FreeBSD file server. I have one generic Gentoo install that I 
periodically chroot into and update. After updating, all of the 
individual frontends get shut down, new base images are cloned off that 
generic volume, and the frontends boot into them. On the first boot, 
they rsync their own custom overlay and reboot.

The generic Gentoo volume is nothing more than the manual install 
directions, starting from a stage3 tarball. I do need a custom initrd, 
with a handful of iSCSI libraries and helper applications, to mount and 
pivot into the iSCSI volume. Since all the frontends are clones off the 
master, they only store changes from the master (typically logs and 
themecache), and thus only amount to a few hundred MB before they get 
refreshed. Since they are independent volumes, I can store as many old 
copies as I want, meaning all I need to do to rollback is select one of 
the old images through the PXELinux menu. As far as Linux is concerned, 
you're just using a normal partition on a normal disk, so there is no 
need for shared read-only mounts or funky union/aufs overlays.

I can't claim it's a fast boot. As with any network boot, you're going 
to have a good 15-20 seconds just waiting for the PXE boot rom to 
initialize and do it's thing. Once you get past that, my kernel plus 
embedded initrd is only 5.5MB, so your boot speed depends on the type of 
storage you have on the file server.