[gPXE] FW: environment variable expansion in 'filename'?

[Miller, Shao]

Hey again Jarrod,

I'm forwarding this on to the gPXE list.

gPXE actually does support conditionals right now, though they're extremely icky.  See "crazy scripting library" thread[1] or "fall-back filename" thread[2].  However, there doesn't seem to be much interest, much time, much support, much discussion, or some combination thereof for a couple of [relatively] recent proposals to enhance gPXE's scripting/CLI system[3].

- Shao Miller

[1] http://etherboot.org/pipermail/gpxe/2010-March/000646.html
[2] http://etherboot.org/pipermail/gpxe/2010-April/000846.html
[3] http://etherboot.org/pipermail/gpxe-devel/2010-March/000102.html

________________________________________
From: Jarrod Johnson [mailto:jarrod.b.johnson at gmail.com] 
Sent: Thursday, May 20, 2010 14:19
To: Miller, Shao
Subject: Re: [gPXE] environment variable expansion in 'filename'?

So, currently, that's how it goes and I used fixed-address declarations so looking up the 'best' next-server isn't too hard.  Without fixed-address, things start getting tricky based on what I'm trying to do.  While still possible for me to externally coordinate what network the booting device will land in, it would be much simpler for my purposes to inherit 'next-server' from the 'subnet {}' portion of dhcp, but I need to specify per-node paths at a host declaration level.  Things get hypothetically trickier if netboot with DHCPv6 comes into life following the rule in DHCPv6 where DUID is constant regardless of interface when I'm dealing with multihomed devices.  There I might have a single host declaration that has to describe two network relationships, but that's all theoretical.

On a related note, is it horribly objectionable or a bad idea for expand_command  from exec.c to be called from boot_next_server_and_filename from autoboot.c?  Failing that I'll contemplate an embedded script, but lack of conditionals is gPXE scripting could prove to be a touchy thing.