[Crash-utility] determining a "valid" vmcore

[Dave Anderson]

Andrew Hecox wrote:
> hello,
> 
> I'm looking at a customer issue where diskdumpmsg is unable to read a
> vmcore file. It is not clear if this a problem with the vmcore file or
> diskdumpmsg. I can load the vmcore with crash and in my naive usage of
> it, can see no problems. However, I'm new to the tool so that doesn't
> give me a lot of confidence. 
> 
> Does anyone have any suggestions on how or if I can use crash to help
> determine if there's corruption in the vmcore file? Or any other way of
> approaching the problem? 
> 
> Thanks much,
> 
> Andrew
> 

I'm not sure what you expect the crash utility to do -- if it comes
up to a prompt with no error or warning messages, it means that the
ELF header contains what appears to be valid usable information,
and that the minimum kernel memory contents required to set up the
crash utility's notion of the running system are all in place.  That's
not to say that there is no chance that the vmcore contains some
corruption that was not recognized.

With respect to diskdumpmsg, as I understand it, it was fairly recently
changed from a perl script to a C file so that it could be run
earlier in time so as to be able to use the swap partition.  Looking
at main() in the diskdumpmsg.c file (version 1.4.1-2), there are numerous
error types and associated error messages.  What do you mean when you
say that "diskdumpmsg is unable to read a vmcore file"?

Dave