[Crash-utility] dmesg content from crash without debug symbols

[Dave Anderson]

----- Original Message -----
> Hello,
> 
> Is it possible to extract the content of the kernel buffer (result of
> the 'log' command) from a kernel dump without access to the kernel debug
> symbols ?
> 
> The intent is to be able to retrieve a minimal set of information from
> the dump on a system that doesn't have to possibility to install the
> namelist with debug symbols.
> 
> TIA,
> 
> Kind regards,
> 
> ...Louis
> --
> Louis Bouchard
> Backline Support Analyst
> Canonical Ltd
> Ubuntu support: http://landscape.canonical.com

Do you guys (Ubuntu) have makedumpfile as part of your kdump facility?
It does just that, using the debug/offset information contained in
the vmcoreinfo data:

 $ man makedumpfile
 ...
       --dump-dmesg
              This option  overrides  the  normal  behavior  of  makedumpfile.
              Instead  of  compressing  and  filtering  a  VMCORE  to  make it
              smaller, it simply extracts the dmesg  log  from  a  VMCORE  and
              writes it to the specified LOGFILE. If a VMCORE does not contain
              VMCOREINFO for dmesg, it is necessary to specfiy [-x VMLINUX] or
              [-i VMCOREINFO].

              Example:
              # makedumpfile --dump-dmesg /proc/vmcore dmesgfile
              # makedumpfile --dump-dmesg -x vmlinux /proc/vmcore dmesgfile
 ...

Dave