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. If a directory is not specified, then
/var/crash is used.
The kernel and core file can then be analyzed using various tools, including
crash(8),
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 hardware faults or kernel bugs. If a kernel
bug is suspected, a full bug report should be filed at
http://www.netbsd.org/, or
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 (potentially
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
invocations of savecore will ignore it.
-
-
- -f
- Forces a dump to be taken even if the dump doesn't appear
correct 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
information 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
successfully runs.
savecore also checks the available disk space before
attempting to make the copies. If there is insufficient disk space in the file
system containing
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),
crash(8),
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.