dmesg (1)
NAME
dmesg - print or control the kernel ring bufferSYNOPSIS
dmesg [options]dmesg --clear
dmesg --read-clear [options]
dmesg --console-level level
dmesg --console-on
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=daemonwill 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,warnwill 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 <kzak@redhat.com> Theodore Ts'o <tytso@athena.mit.edu>
AVAILABILITY
The dmesg command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.