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dmesg(8) [bsd man page]

DMESG(8)						      System Manager's Manual							  DMESG(8)

dmesg - collect system diagnostic messages to form error log SYNOPSIS
/sbin/dmesg [ - ] DESCRIPTION
N.B.: Dmesg is obsoleted by syslogd(8) for maintenance of the system error log. Dmesg looks in a system buffer for recently printed diagnostic messages and prints them on the standard output. The messages are those printed or logged by the system when errors occur. If the - flag is given, then dmesg computes (incrementally) the new messages since the last time it was run and places these on the standard output. FILES
/usr/adm/msgbuf scratch file for memory of - option SEE ALSO
syslogd(8) 4th Berkeley Distribution November 17, 1996 DMESG(8)

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DMESG(1)							   User Commands							  DMESG(1)

dmesg - print or control the kernel ring buffer SYNOPSIS
dmesg [options] dmesg --clear dmesg --read-clear [options] dmesg --console-level level dmesg --console-on dmesg --console-off DESCRIPTION
dmesg is used to examine or control the kernel ring buffer. The default action is to read all messages from kernel ring buffer. OPTIONS
The --clear, --read-clear, --console-on, --console-off and --console-level options are mutually exclusive. -C, --clear Clear the ring buffer. -c, --read-clear Clear the ring buffer contents after printing. -D, --console-off Disable printing messages to the console. -d, --show-delta Display the timestamp and time delta spent between messages. If used together with --notime then only the time delta without the timestamp is printed. -E, --console-on Enable printing messages to the console. -f, --facility list Restrict output to defined (comma separated) list of facilities. For example dmesg --facility=daemon will print messages from system daemons only. For all supported facilities see dmesg --help output. -h, --help Print a help text and exit. -k, --kernel Print kernel messages. -l, --level list Restrict output to defined (comma separated) list of levels. For example dmesg --level=err,warn will print error and warning messages only. For all supported levels see dmesg --help output. -n, --console-level level Set the level at which logging of messages is done to the console. The level is a level number or abbreviation of the level name. For all supported levels see dmesg --help output. For example, -n 1 or -n alert prevents all messages, except emergency (panic) messages, from appearing on the console. All levels of messages are still written to /proc/kmsg, so syslogd(8) can still be used to control exactly where kernel messages appear. When the -n option is used, dmesg will not print or clear the kernel ring buffer. -r, --raw Print the raw message buffer, i.e., don't strip the log level prefixes. -s, --buffer-size size Use a buffer of size to query the kernel ring buffer. This is 16392 by default. (The default kernel syslog buffer size was 4096 at first, 8192 since 1.3.54, 16384 since 2.1.113.) If you have set the kernel buffer to be larger than the default then this option can be used to view the entire buffer. -T, --ctime Print human readable timestamps. The timestamp could be inaccurate! The time source used for the logs is not updated after system SUSPEND/RESUME. -t, --notime Don't print kernel's timestampts. -u, --userspace Print userspace messages. -V, --version Output version information and exit. -x, --decode Decode facility and level (priority) number to human readable prefixes. SEE ALSO
syslogd(8) AUTHORS
Karel Zak <> Theodore Ts'o <> AVAILABILITY
The dmesg command is part of the util-linux package and is available from util-linux July 2011 DMESG(1)
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