This week-end, I've completely rewritten the patch I wrote a week ago
to dump kernel messages to a floppy disk. Based on a comment from Pavel
Machek, I've removed the kernel panic message (which is nearly useless,
and available in kernel messages buffer), and replaced it with kernel
messages buffer. That's now 16 kbytes of last kernel messages that can
be dumped to a diskette. Gilbert Ramirez also asked me to allow a dump
onto a FAT filesystem. Pavel thought this might be very dangerous because
people could believe this won't destroy their data. I agree with this, but
this can be useful and people ask for it... so I've implemented it as an
option (at compile time), with lots of warnings.
Now there are two cases in which you can get a dump :
- by pressing SysRQ-D
- by waiting for a kernel panic. In this case, the kernel waits during
panic_timeout for an eventual SysRQ, and then switches to real mode
and dumps the messages. After that, it can automatically reboot.
There are more combinations which can be used, you should take a look
at the patch and/or the doc. I've written a page which goes to
Documentation/kmsgdump.txt, and some little help for the compilation
options (This feature can be enabled or disabled with make menuconfig,
just after SysRQ).
Well, this time I won't send the patch uuencoded here, because if everyone
does this, the LKML will grow quickly :-)
You can retrieve it from :
http://www-miaif.lip6.fr/willy/pub/linux-patches/kmsgdump/
Ah, last note: it's for x86 architecture only :-(
If someone is interested in porting it to other architectures, that would
be interesting, IMO.
Well, please tell me what you think of it. Is it as bad as the first one,
or does it begin to be useful ? If this is the case, I'll add runtime
configuration options to it (not very difficult now).
Have a nice week,
Willy
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