Jun Koi wrote:
On Tue, Sep 23, 2008 at 12:49 AM, Dave Anderson <anderson@xxxxxxxxxx> wrote:
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.
Sorry for stupid question, but how to have /dev/crash device?
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".
That is more clear now for me. But how about the "-reloc" param?
Again, that was for a particular series of Fedora x86 kernels.
Here are the details:
http://people.redhat.com/anderson/crash.changelog.html#4_0_4_5
The Fedora kernel configuration was changed.
Besides, I also found some options not documented anywhere, like "-g".
That was put in some years ago to quickly determine whether a vmlinux
file was built with -g, and then bail out without running a session.
Way back then it was pretty much up to the user to re-compile his own
kernel with -g, i.e., prior to the distros providing debug-full vmlinux
files.
Dave
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