[Crash-utility] question on some command params

[Dave Anderson]

Jun Koi wrote:
> Hi,
> 
> I found below cmdline params having no documentation anywhere, so
> could somebody explain their meaning?
> 
> - memory_module
> - no_modules
> - no_ikconfig
> - no_namelist_gzip
> - no_kmem_cache
> - kmem_cache_delay
> - readnow
> - buildinfo
> - zero_excluded
> 
> 
> Many thanks,
> J

They're all essentially debug flags for use on kernels/dumpfiles
that for some reason or other would not initialize properly.

memory_module: if /dev/mem or /dev/crash do not suffice you could
   force-feed one or the other for live system analysys.

no_modules: if the module initialization code cause crash to
   during initialization, skip it with --no_modules.

no_ikconfig: if the reading of the in-kernel config data causes
   an initialization-time failure, skip it with --no_ikconfig

no_namelist_gzip: completely obsolete

no_kmem_cache: if the kmem slab cache initialization causes an
   initialization-time failure, skip it with --no_kmem_cache

kmem_cache_delay: if the kmem slab cache initialization causes an
   initialization-time failure, it can alternatively be delayed
   until the first command that accesses the kmem_cache is run

readnow: useless now, but there was a very short period of time
   where gcc was creating debuginfo vmlinux files that required
   --readnow in order to gather all of the debug data at initialization
   time.

buildinfo: dumps information about who/where/when/gcc w/respect to
   the crash utility itself.

zero_excluded: if a page was excluded by diskdump or makedumpfile,
   it normally returns a failure if the page is accessed.  If you
   want it to just return a page of zeroes, use --zero_excluded.

In any case, if you find that you need to use any of the flags above,
then it's indicative of (1) a crash utility bug, or (2) a corrupted vmcore.
In either situation, it's best to find and fix the underlying problem
instead of working around it.  Using the flags above is only a stop-gap
measure, and should not be "depended upon".

Dave