Making sense of a system coredump

lance.norskog lance at motcsd.csd.mot.com
Wed Jun 19 10:43:26 AEST 1991


This does not answer his problem, but does explain how to crash on 386 UNIX.
(I cannot afford SGI gear, alas.)

When Unix does a panic and saves all its RAM to disk, it dumps it into
the swap area.  

After it reboots, it asks you if you want to save the core dump.
If you save it to tape, you get a raw disk dump of the swap area.
You can then 'dd' the tape into a Unix file, and run
	/etc/crash -d /tmp/bigcore -n /unix

I took this question out of the system start-up, and just run
	/etc/crash -d /dev/swap
after the system startup script does its endless disk preening.

There's a trick here: the system startup scripts run one program
at a time.  With even a 4 megabyte system, it never really needs to
page any data out before that first console login prompt.  So, your
panic dump is still intact in /dev/swap.

You can verify this by running '/etc/swap -l'.

Lance Norskog



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