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savecore(8)
NAME
savecore - Copies a core dump from swap partitions to a file
SYNOPSIS
/sbin/savecore [-efnpPstv] directory
/sbin/savecore [-d header-dev [-d header-dev]] \ directory
/sbin/savecore -c
/sbin/savecore -T devno:devpath
OPTIONS
-c (clear)
Clears any core dumps from the swap partitions without saving the dump.
As nothing is saved, there is no need to specify the directory in which
to save the core file. Only The -d and -v flags can be used in
combination with the -c flag. See also the -P (print) option.
-d header-dev (device)
The -d flag causes the savecore command to look for the dump header in
the partition specified by header-dev. This flag is useful when the dump
header is stored in a partition other than those partitions searched by
default. Normally just the primary swap partition is searched. You may
want savecore to search elsewhere if you expect the dump header to be in
a different location, for example:
1.
You changed the way that swap partitions are assigned in /etc/fstab,
/sbin/swapdefault, and/or /etc/sysconfigtab, but, at the time of the
crash, you had yet to force the swapper to conform to the settings.
2.
You crashed running with root on one drive, but have rebooted and are
running savecore with root on another drive with different swap
partition assignments. (Note that in this case savecore will also copy
the wrong vmunix to directory/vmunix.n, and you will need to replace it
with a copy of the correct vmunix file from the root that crashed.)
3.
The primary swap device had soft failed before the crash (possibly
causing the crash), and the dump code placed the header on the first
working swap device, which will not be the primary swap.
Note
There is a defunct kernel variable called dumpdev, which
specifies the dev_t of a partition in which savecore should look
for a header by default. Use of the dumpdev variable should be
avoided, and you should verify that it is not set. Should
dumpdev be set to a partition other than primary swap, you might
forget to change that setting if you later change its use to a
file system instead of swap space. If this happens, and there is
a system crash, the dump will write on the data partiton,
destroying your data.
The header-dev is interpreted relative to the current directory at the
time that savecore is invoked. Since disk partitions are usually found
in /dev or in subdirectories thereof, you must supply the full pathname
of the partition, such as:
/dev/disk/disk0h
It is meaningful to specify this flag up to two times. The first time
that it is specified, it is used instead of the dumpdev setting found via
getsysinfo(GSI_DUMPDEV). The second time that it is specified, it is
used in place of the primary swap partition. Note that the specification
must be separated from the flag (or flags) by whitespace.
-e (error logs)
Specify the -e flag to save only the kernel message buffer and binary
event log buffers from the dump. Other information in the crash dump,
such as the copy of physical memory, is not saved.
-f (force)
Specify the -f flag to copy the dump even if there appears to be
insufficient storage space on the specified filesystem to save both the
dump and the copy of vmunix file. Although space may appear to be
insufficient, there might be enough because you run savecore as root
(superuser). This enables the savecore program to use space normally
reserved to help control fragmentation. Also, if the specified directory
contains a minfree file (see below) estimates of available space may be
very conservative.
It may be that the dump fits in the available space, but the copy of
vmunix does not. You can recover from this by running /usr/bin/crashdc
manually and specifying the actual location of the vmunix file.
If the dump itself will not fit, then only the portion of the dump that
fits in the space available is copied. Such a truncated dump may work
if it is not a compressed dump, but truncation of a compressed dumps will
render it useless.
-n (no clear)
Specify the -n flag to prevent the savecore program from clearing the
dump header out of the partitions in which it was found (after saving the
dump, and/or message buffer and binary event log). This is intended as a
debugging flag but it could allow you to run savecore once with the -e
and -n flags, and then with the -s flag and a different directory.
-p (print)
The -p option is used when debugging the dump system. It produces
printouts of interest only to a savecore/dumpsys developer.
-P (print)
The '-P' option searches for a crash dump and, if found, will display its
dumpinfo header. The dump header structure is defined in
/usr/include/sys/sysinfo.h. No directory need be specified since nothing
is saved. The savecore utility then exits, leaving any existing crash
dump intact. See also the -c (clear) option.
-s (simple)
Specify the -s flag to prevent the savecore program from saving the
message buffer and binary event log, and prevent copying of the vmunix
file.
-t (tell)
Specify the -t flag to produce an exit value of 4 when no dump is found.
Normally, not finding a dump is not considered an error, and the default
exit value is 0. It is also 0 when a dump is saved successfully.
Scripts such as /sbin/init.d/savecore depend upon this behavior. You may
want to write scripts which need to distinguish between finding and not
finding a dump and the -t flag can be used in such scripts.
-T devno:devpath (translate)
This option supplies translations from the kernel dev_t device numbers to
file system device paths. Any number of translations may be specified and
each must be preceded by the '-T' option. This option is only required
when the saved device number(s) do not match the file system devices on
which the crash dump was written. For example, The following option:
-T 0x13007f3:/dev/disk/dsk0b
maps device number x13007f3 to disk partition /dev/disk/dsk0b.
-v (verbose)
Specify the -v flag to display messages about the operation of savecore.
DESCRIPTION
The savecore command is usually invoked automatically during system
startup. It determines whether a crash dump has been made, and if there is
enough file system space to save it (see the following information about
minfree). If you specify the -f flag, savecore copies the dump even if
there seems to be insufficient file space. If space is insufficient, only
a portion of the dump is saved into the crash dump file but note that
truncated compressed dumps will not be usable. Information is stored in the
/var/adm/crash directory by default.
The crash dump contains the copy of a selected portion of physical memory
(or all of physical memory in the case of a full crash dump) as of the time
of the crash. The savecore command saves this information in the file
vmzcore.n if the dump is in the compressed from, or in the file vmcore.n if
in the non-compressed form. The command also copies the kernel executable
image, usually /vmunix, (or whatever UNIX image filename was recorded as
the name of the booted file) to the /var/adm/crash/vmunix.n file. You
analyze the vmzcore.n (or vmcore.n) and vmunix.n files to determine the
cause of the crash. (See the Kernel Debugging manual for information about
analyzing crash dump files.)
Note
In the case of a boot linked kernel, which has no image file to
copy, the linker will be invoked to create one from suitable
modules.
In the dump filename, the variable n indicates the sequential number of the
crash. For the first crash, savecore creates the files vmunix.0 and
vmzcore.0 (or vmcore.0). It then creates a file named directory/bounds
and initializes the file with the value 1. For each succeeding crash, the
savecore command uses the value in the directory/bounds file and then
increments that value.
The file directory/minfree specifies the minimum number of kilobytes that
must be left on the filesystem containing directory after savecore copies
the crash dump. By default, this file does not exist, indicating that the
minimum is zero. To specify a minimum, create the file and store the
number of kilobytes you want reserved in it. You can override the setting
in directory/minfree using the -f flag.
In addition to saving the crash dump, the savecore command writes a reboot
message to the /var/adm/syslog/auth.log file. If the system crashed as a
result of a panic, savecore includes the panic string in that log file. You
can cause savecore to write the message to another file by modifying the
auth facility entry in the /etc/syslog.conf file. See the syslogd(8)
reference page for information about modifying /etc/syslog.conf.
The savecore command also attempts to save the kernel message buffer and
binary event log buffers from the dump. The kernel message buffer is saved
in the /var/adm/crash/msgbuf.savecore file, by default. The binary event
log buffer is saved in the /var/adm/crash/binlogdumpfile file by default.
When the syslog and binlog daemons are initialized later during system
startup, they check for the saved buffer files. The daemons process and
delete the files.
You can change the location to which savecore writes the kernel message
buffer and binary event log. To change the location for saving the kernel
message buffer, modify the msgbuf.err entry in the /etc/syslog.conf file.
To change the location for saving the binary event log, modify the dumpfile
entry in the /etc/binlog.conf file. If you remove either the msgbuf.err or
dumpfile entry from the configuration files, savecore does not save the
corresponding buffer. For most entries, the /etc/syslog.conf and
/etc/binlog.conf files allow you to forward messages to another system.
However, you cannot specify a forwarding address in the msgbuf.err and
dumpfile entries. For more information, see syslogd(8) and binlogd(8).
The default location for saving crash dump files is /var/adm/crash. To
modify the default location, issue the following command:
> /usr/sbin/rcmgr set SAVECORE_DIR <directory>
The default behavior of savecore is to return to single-user mode if it is
unable to save a core dump because of insufficient filesystem space. This
feature can be disabled as follows:
/usr/sbin/rcmgr set SAVECORE_FLAGS M
FILES
/sbin/savecore
Specifies the executable file.
directory/bounds
Specifies the number of the filename for the next dump.
directory/minfree
Specifies the minimum number of kilobytes to be left after crash
dump files are written.
/etc/syslog.conf
System logging configuration file.
/etc/binlog.conf
Binary logging configuration file.
/var/adm/crash
Default location of the dump file and the vmunix.n copy.
/var/adm/crash/msgbuf.savecore
The default location of the file in which the crashed system's
kernel message buffer is saved.
/var/adm/crash/binlogdumpfile
The default location of the file in which the crashed system's
binary event log buffer is saved.
RELATED INFORMATION
Commands: dumpsys(8), expand_dump(8) rcmgr(8)
Daemons: binlogd(8), syslogd(8)
Kernel Debugging, System Administration
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