Re: [PATCH] pypxeboot bootloader

[Stephen Childs <Stephen.Childs@cs.tcd.ie>]

Tim Deegan wrote:
> First impressions: this looks really useful but has a few rough edges
> that need to be knocked off.  (I haven't had a chance to try this on a
> real machine yet.)

I absolutely agree, this was the first working version and I was aware 
there were nasties in it.

>> +for line in udhcplines:
>> +    s = line.strip()
>> +    f = s.split()
>> +
>> +    if s[0]=='{' and s[-1]=='}':
>> +        dhcpinfo=eval(s, {"__builtins__" : {}})
>> +        for k in dhcpinfo:
>> +            dhcpinfo[k]=dhcpinfo[k].strip()
> 
> Executing the results of programs scares me.  Could you just parse it?

Yes quite. Sorry that was cut-and-paste code so I didn't think about it 
enough. Will rewrite.

>> +ipaddr=dhcpinfo['ip']
>> +ipaddrlist=ipaddr.split('.')
>> +hexip=commands.getstatusoutput("/usr/bin/gethostip -x "+ipaddr)[1]
> This requires syslinux to be installed on the Xen host, and isn't 
> hard to do by hand: "%2.2x%2.2x%2.2x%2.2x" % tuple(map (int, ipaddrlist))
> (I'm sure more heavyweight python hackers can correct my style.)

Yes of course I'll change that.

>> +tmpdir="/var/lib/xen/"
>> +
>> +os.chdir(tmpdir)
>> +commandstr="tftp -c get "+servaddr+":pxelinux.cfg/"+hexip
>> +#print "running command "+commandstr
>> +getpxeres=commands.getstatusoutput(commandstr)
> 
> You'll need to be more careful with temporary file names -- here at
> least the filename is unique to the guest (we hope!) but for the kernel
> etc., two boots could clash.  Also, you don't seem to remove the
> downloaded config files.

Yes that all needs tidying up. Unfortunately the version of tftp I was 
using didn't actually support "get <remote-file> <local-file>" as 
advertised which I was initially going to use. I'll have to download to 
the filename supplied by the server then move to a tmpfile.

On the subject of removing files yes of course I'll remove the config 
files. Comparing with pygrub, that seems to leave kernels and initrds 
clogging up /var/lib/xen, and I suppose I'll end up doing the same. I 
suppose you could set up tmpwatch to clean it up, but it still seems a bit 
messy.

Expect a new patch soon ...

Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs