[mythtv-users] Diskless Front End (again)

[Jeff Coffler]

I have netboot working successfully on FC6.

My server is an FC6 system, and my clients are FC6 systems as well.  The 
server and client run different kernel versions.

I need learn some things when looking at the Wiki on this stuff.  First, 
if you haven't looked at the Wiki, you MUST:

http://www.mythtv.org/wiki/index.php/Diskless_Frontend#Redhat_and_Fedora_Core

It's a fantastic starting point.

Second, system-config-netboot in FC6 works just fine for setting all 
this up, although the final environment does need a bit of tweaking.  
Lastly, there is some documentation available from RedHat on this:

http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/sysadmin-guide/

See chapters 3 and 4.

Now, the things I learned along the way:

1. IMPORTANT!  When you run system-config-netboot, it makes changes to 
the diskless boot root area.  For example, /etc/mtab is modified to be a 
symbolic link to /proc/mounts.  When you run system-config-netboot, it 
creates "marker" files to it knows it did this stuff.  But if you change 
things in the diskless boot root area "behind it's back", you can 
seriously confuse things.  End result: If you make changes to the "boot" 
system on the original hard drive, I've found it's best to blow away the 
root on your server and rsync it again.  (-del may work on the rsync; I 
haven't tried that.)

2. Follow the directions in the WIKI *exactly*.  If you're in trouble, 
blow away your root area and start all over again from scratch.  
Deviation will cause grief.  For example, I thought "Hey, I can just 
maintain hard links and save disk space!"  Nope; when I tried rsync to 
maintain hard links, errors followed.

3. After you get the root area rsync'ed, and you run 
system-config-netboot to create the boot images on your server, then you 
need to mount the boot image via loopback and make the following changes:

3a) Copy mount.nfs from <diskless-boot-root>/sbin/mount.nfs to 
<boot-image)/sbin/mount.nfs
3b) In the disklessrc file (in / of the diskless-boot-root image), do:
3b.1) Modify the mount of the .snapshot area to include -n (no write 
access to /etc),
3b.2) Add a line after that mount to remount the .snapshot area RW (not 
sure why it gets mounted RO, but it does)

After all that is done, umount the loopback image, recompress it, and 
copy it to the boot image on the server for the diskless system.

I found that 3a was in the Wiki link, as well as 3b.2, but 3b.1 wasn't 
there.

After doing all this, I got my FC6 system netbooting.  It's a good thing.

One other tidbit:

I use mythvideo, so I want video content mounted from the server.  I 
found that putting this in the snapshot's /etc/fstab file didn't work 
(again, no write access to /etc for the mtab tmp file).  So I don't do 
this, but instead modified /videos/addons (on the diskless boot system) 
to be a symbolic link to "/net/<server-name>/<export-path to addons 
directory on server>" (i.e. I get at it via automount).  This eliminates 
the problem for me, and allows me to use MythVideo properly on the 
diskless boot system.

Hope this helps.  If someone else gets this working successfully 
following my instructions, let me know, and I'll update the Wiki!

    -- Jeff