savecore(8) - NetBSD Manual Pages

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SAVECORE(8)             NetBSD System Manager's Manual             SAVECORE(8)


NAME

     savecore - save a core dump of the operating system


SYNOPSIS

     savecore -c
     savecore [-fvz] [-N system] directory


DESCRIPTION

     When the NetBSD kernel encounters a fatal error, the panic(9) routine ar-
     ranges for a snapshot of the contents of physical memory to be written
     into a dump area, typically in the swap partition.

     Upon a subsequent reboot, savecore is typically run out of rc(8), before
     swapping is enabled, to copy the kernel and the saved memory image into
     directory, and enters a reboot message and information about the core
     dump into the system log.

     The kernel and core file can then be analyzed using various tools, in-
     cluding dmesg(8), fstat(1), gdb(1), iostat(8), netstat(1), ps(1), and
     pstat(8), to attempt to deduce the cause of the crash.

     Crashes are usually the result of kernel bugs; if this is suspected, a
     full bug report should be filed using send-pr(1), containing as much in-
     formation as possible about the circumstances of the crash.  Since crash
     dumps are typically very large and may contain whatever (potentially con-
     fidential) information was in memory at the time of the crash, do NOT in-
     clude a copy of the crash dump file in the bug report; instead, save it
     somewhere in the event that a NetBSD developer wants to examine it.

     The options are as follows:

     -c         Only clears the dump without saving it, so that future invoca-
                tions of savecore will ignore it.

     -f         Forces a dump to be taken even if the dump doesn't appear cor-
                rect or there is insufficient disk space.

     -N         Use system as the kernel instead of the default ``/netbsd''.

     -v         Prints out some additional debugging information.

     -z         Compresses the core dump and kernel (see compress(1)).

     savecore checks the core dump in various ways to make sure that it is
     current and that it corresponds to the currently running system.  If it
     passes these checks, it saves the core image in directory/netbsd.#.core
     and the system in directory/netbsd.# (or in directory/netbsd.#.core.Z and
     directory/netbsd.#.Z, respectively, if the -z option is used).  The ``#''
     is the number from the first line of the file directory/bounds, and it is
     incremented and stored back into the file each time savecore successfully
     runs.

     savecore also checks the available disk space before attempting to make
     the copies.  If there is insufficient disk space in the filesystem con-
     taining directory, or if the file directory/minfree exists and the number
     of free kilobytes (for non-superusers) in the filesystem after the copies
     were made would be less than the number in the first line of this file,
     the copies are not attempted.

     If savecore successfully copies the kernel and the core dump, the core
     dump is cleared so that future invocations of savecore will ignore it.

     savecore is meant to be called near the end of the initialization file
     /etc/rc (see rc(8)).


FILES

     /netbsd    current kernel


BUGS

     The minfree code does not consider the effect of compression.


SEE ALSO

     compress(1), dmesg(8), fstat(1), gdb(1), iostat(8), netstat(1), ps(1),
     pstat(8), panic(9), rc(8), send-pr(1), syslogd(8)


HISTORY

     The savecore command appeared in 4.1BSD.

4th Berkeley Distribution        June 5, 1993                                2