[gPXE] fall-back filename

[Miller, Shao]

Good day Alex,

In regards to booting a fall-back URI in case DHCP does not provide a
boot filename option:

Yes, it can currently be done in a very ugly fashion using gPXE's
current scripting system.  It does, however, depend on the 'dhcp'
command not failing.  If your 'dhcp' command is guaranteed to work, but
possibly not return a boot filename, then this is fine.

There has been discussion regarding scripting amongst the gPXE
developers' e-mail mailing-list, but the discussion is slow-going and
none of the patches submitted there have been agreed upon by all, and so
have not been committed to gPXE's official codebase.  Maybe some day...

In the meanwhile, you could have a look at including "lib.gpxe"[1] at
the top of your script, then using the '${if1}', '${if2}', '${if3}' and
'${cond}' items to accomplish your conditional choice.

Sorry.

- Shao Miller

[1] http://etherboot.org/pipermail/gpxe/2010-March/000646.html  In
particular, the attachment[2]
[2]
http://etherboot.org/pipermail/gpxe/attachments/20100317/99a626bd/attach
ment.obj