[uml-user] UML newbie - "nslookup and networking" problems resolved with SKA

[Simon W. <si...@zy...>]

Hi,

been lurking on IRC etc trying to get my first UML instances up and stable.

Was running Debian testing on host, with the various Debian UML packages 
loaded from the other versions, and the Debian stable file system from the 
usermodelinux.org site.

Had a lot of problems getting networking working, and stable, despite 
considerable firewall, and some bridging experience.

With a vanilla 2.4.27 Debian kernel, and;

Linux version 2.4.26-3um (root@mizar) (gcc version 3.3.4 (Debian 1:3.3.4-11)) 
#2 Wed Sep 8 18:07:31 PDT 2004

I failed to get a stable networking setup - problem was that the UML instance 
would hang (or sometimes just the networking, until the tuntap uinterface was 
taken out of the bridge, reset, and brought up again). This would happen 
frequently, and everytime "nslookup" was run in the UML. 

Running "strace nslookup" in the UML worked fine, running strace against the 
UML produce 69MB of indecipherable loopings and a UML so slow I wasn't sure 
if it had hung or not <sigh>.

Anyway it seems that switching to a host kernel 2.4.25 with the SKA patch in 
(as per one of the Debian stable UML "HOWTO"'s) solved the problem. I assume 
some sort of race condition, that the SKA patch addresses.

Seems at least with that combination the SKA patch is mandatory for stability 
of the UML. However it isn't clear to me that the SKA patch is "mandatory" 
from my initial reading of the documentation - desirable yes - but it looks 
to me like it is mandatory.

I was also a bit disappointed some of the documentation was so "dated", lots 
of it, much of it very good, but contradictory due to age, and a lot refers 
to old stuff that is of little current interest.

I don't know enough yet to write new documentation, but I'd happily put in a 
little time to "tidy up" some of the existing documentation.