Starting FAI off a running system

[Holger Parplies]

Hi,

Toomas Tamm wrote on 2011-10-11 19:27:30 +0300 [Starting FAI off a running system]:
> I have a host which has a very old version of Linux installed on the
> hard disk. I also have a bootable USB stick which contains FAI and can
> install a newer version of Debian on other hosts. The motherboard on
> that old machine does not seem to be able to boot neither off the
> network nor off that USB stick.
> 
> Assuming I can mount the filesystem on the FAI USB stick under the
> already-installed system, is it possible to start FAI and reinstall the
> system? Any hints at how to do that?

you could do a 'dirinstall', but that would mean installing onto new
partitions and keeping the old ones around (at least until the new system is
running). What I do in similar cases is:

* Copy the install kernel (e.g. /srv/tftp/fai/vmlinuz-install) and the
  corresponding initrd from the FAI server to the client.
* Add an entry to the LILO or GRUB configuration to boot that kernel with
  the same command line arguments you would find in the file created by
  'fai-chboot' for that host in /srv/tftp/fai/pxelinux.cfg - I tend to name
  the entry "Fully Automatic Installation" :).
  You'd need to adapt this to using the USB stick as root rather than the
  $NFSROOT if that's what you want to use.
* Reboot the host and select the new entry when convenient.
* Hope the installation succeeds or aborts prior to task_partition :-).

You can do much the same for a 'sysinfo' if you want to do a non-destructive
test first.

If the installation does fail before making the new system bootable, you're
probably stuck to connecting a CDROM drive and booting a rescue system :-(.
It *has* happened to me at least once (which was my fault, not FAI's), but
mostly, it just works as intended.

Hope that helps.

Regards,
Holger