crash(8v)crash(8v)Namecrash - what happens when the system crashes
This section explains what happens when the system crashes and shows
how to analyze crash dumps.
When the system crashes voluntarily it prints a message on the console
in the form:
The system takes a dump on a mass storage peripheral device, and then
invokes an automatic reboot procedure as described in Unless there is
some unexpected inconsistency in the state of the file systems due to
hardware or software failure, the system then resumes multi-user opera‐
tions. If auto-reboot is disabled on the front panel of the machine,
the system halts at this point.
The system has a large number of internal consistency checks; if one of
these fails, it prints a short message indicating which one failed.
The most common cause of system failures is hardware failure. In all
cases there is the possibility that hardware or software error produced
the message in some unexpected way. These messages are the ones you
are likely to encounter:
IO err in push
hard IO err in swap
The system encountered an error when trying to write to the pag‐
ing device or an error in reading critical information from a
disk drive. Fix your disk if it is broken or unreliable.
timeout table overflow
Due to the current data structure, running out of entries causes
a crash. If this happens, make the timeout table bigger.
KSP not valid
CHM? in kernel
These indicate either a problem in the system or failing hard‐
ware. If SBI faults recur, check out the hardware or call field
service. Run the processor microdiagnostics to determine if the
problem is caused by an unreliable processor.
machine check %x:
machine dependent machine-check information
Call field service.
trap type %d, code=%d, pc=%x
An unexpected trap has occurred within the system; the trap
0 reserved addressing fault
1 privileged instruction fault
2 reserved operand fault
3 bpt instruction fault
4 xfc instruction fault
5 system call trap
6 arithmetic trap
7 ast delivery trap
8 segmentation fault
9 protection fault
10 trace trap
11 compatibility mode fault
12 page fault
13 page table fault
The most common traps in system crashes are trap types 8 and 9,
indicating a wild reference. The code is the referenced
address, and the pc at the time of the fault is printed. These
problems tend to be easy to track down if they are kernel prob‐
lems because the processor stops, but there are random occur‐
rences with unpredictable causes.
The system initialization process has exited. The only solution
is the automatic reboot procedure described in Until this is
done, no new users can log in.
When the system crashes, it attempts to write an image of memory into
the back end of the primary swap area. After the system is rebooted,
the program runs and preserves a copy of this core image and the cur‐
rent system in a specified directory for later access. See for
To analyze a dump, you should begin by running with the flag on the
core dump. Normally, the command provides a stack trace from the point
of the crash and this should provide a clue as to what went wrong.
See Alsoadb(1), reboot(8), savecore(8)