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PANIC(8S)                                                            PANIC(8S)



NAME
       panic - what happens when the system crashes

DESCRIPTION
       This  section explains what happens when the system crashes and how you
       can analyze crash dumps.

       When the system crashes voluntarily, it displays a message of the form

              panic: why i gave up the ghost

       on the console, takes a dump on a mass  storage  peripheral,  and  then
       invokes  an  automatic  reboot  procedure  as  described  in reboot(8).
       Unless some unexpected inconsistency is encountered in the state of the
       file  systems due to hardware or software failure, the system will then
       resume multiuser operations.

       The system has a large number of internal consistency checks; if one of
       these  fails,  it will panic with a very short message indicating which
       one failed.

       When the system crashes it writes (or at least attempts  to  write)  an
       image  of memory into the back end of the primary swap area.  After the
       system is rebooted, you can run the program savecore(8) to  preserve  a
       copy  of  this  core  image and kernel namelist for later perusal.  See
       savecore(8) for details.

       To analyze a dump you should begin by running adb(1) with the  -k  flag
       on the core dump, as described in

       The most common cause of system failures is hardware failure, which can
       reflect itself in different ways.

       See DIAGNOSTICS for some messages that you  may  encounter,  with  some
       hints  as  to causes.  In each case there is a possibility that a hard-
       ware or software error produced the message in some unexpected way.

FILES
       /vmunix             the system kernel
       /etc/rc.local       script run when the local system starts up

SEE ALSO
       adb(1), old-analyze(8), reboot(8) sa(8), savecore(8)

DIAGNOSTICS
       IO err in push
       hard IO err in swap
                   The system encountered an error trying to write to the pag-
                   ing device or an error in reading critical information from
                   a disk drive.  You should fix your disk if it is broken  or
                   unreliable.
       timeout table overflow
                   This  really  should  not  be  a  panic, but until the data
                   structure is fixed, involved, running out of entries causes
                   a  crash.  If this happens, you should make the timeout ta-
                   ble bigger by changing the value of ncallout in the param.c
                   file, and then rebuild your system.
       trap  type type, pid process-id, pc = program-counter, sr = status-reg-
       ister, context context-number
                   A unexpected trap has occurred within the  system;  typical
                   trap types are:
                   o  Bus error
                   o  Address error
                   o  Illegal instruction
                   o  Divide by zero
                   o  Chk instruction
                   o  Trapv instruction
                   o  Privilege violation
                   o  Trace
                   o  1010 emulator trap
                   o  1111 emulator trap
                   o  Stack format error
                   o  Uninitialized interrupt
                   o  Spurious interrupt

                   The favorite trap types in system crashes are ``Bus error''
                   or ``Address error'', indicating  a  wild  reference.   The
                   process-id  is the ID of the process running at the time of
                   the fault, program-counter is the hexadecimal value of  the
                   program  counter,  status-register is the hexadecimal value
                   of the status register, and context-number is  the  context
                   that the process was running in.  These problems tend to be
                   easy to track down if they are kernel bugs since  the  pro-
                   cessor stops cold, but random flakiness seems to cause this
                   sometimes.

       init died   The system initialization process has exited.  This is  bad
                   news, as no new users will then be able to log in.  Reboot-
                   ing is the only fix, so the system just does it right away.



                               25 September 1987                     PANIC(8S)