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 [-fvz] [-N system] [-Z level] directory
     savecore -c [-v] [-N system]
     savecore -n [-v] [-N system]


DESCRIPTION

     When the NetBSD kernel encounters a fatal error, the panic(9) routine
     arranges 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,
     including 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
     information as possible about the circumstances of the crash.  Since
     crash dumps are typically very large and may contain whatever (poten-
     tially confidential) information was in memory at the time of the crash,
     do NOT include 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         Check whether a dump is present without taking further action.
                The command exits with zero status if a dump is present, or
                with non-zero status otherwise.

     -N         Use system as the kernel instead of the default (returned by
                getbootfile(3)).  Note that getbootfile(3) uses secure_path(3)
                to check that kernel file is ``secure'' and will default to
                /netbsd if the check fails.

     -v         Prints out some additional debugging information.

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

     -Z level   Set the compression level for -z to level.  Defaults to 1 (the
                fastest compression mode).  Refer to gzip(1) for more informa-
                tion regarding the compression level.

     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.gz
     and directory/netbsd.#.gz, 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 suc-
     cessfully runs.

     savecore also checks the available disk space before attempting to make
     the copies.  If there is insufficient disk space in the file system con-
     taining directory, or if the file directory/minfree exists and the number
     of free kilobytes (for non-superusers) in the file system 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.


SEE ALSO

     fstat(1), gdb(1), gzip(1), netstat(1), ps(1), send-pr(1), secure_path(3),
     dmesg(8), iostat(8), pstat(8), rc(8), syslogd(8), panic(9)


HISTORY

     The savecore command appeared in 4.1BSD.


BUGS

     The minfree code does not consider the effect of compression.

NetBSD 5.2.2                   October 16, 2004                   NetBSD 5.2.2