Просмотр сообщений операционной системы при загрузке и настройке
root@OrangePI:~# dmesg
Просмотр сообщений об ошибках
root@OrangePI:~# dmesg | grep error
Просмотр состояния сетевых адаптеров
root@OrangePI:~# dmesg | grep -i Eth
[ 0.658813] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 8.811157] [RDAWLAN_ERR]:<wland_bus_start,104>: nvram:get a random ether address
или так:
root@OrangePI:~# dmesg | grep eth
[ 8.811157] [RDAWLAN_ERR]:<wland_bus_start,104>: nvram:get a random ether address
Просмотр количества доступной в системе памяти:
root@OrangePI:~# dmesg | grep Memory
[ 0.000000] Memory policy: ECC disabled, Data cache writeback
[ 0.000000] Memory: 236MB = 236MB total
[ 0.000000] Memory: 230948k/230948k available, 10716k reserved, 0K highmem

root@OrangePI:~# dmesg —help

dmesg [options]

-C, —clear clear the kernel ring buffer
-c, —read-clear read and clear all messages
-D, —console-off disable printing messages to console
-E, —console-on enable printing messages to console
-F, —file <file> use the file instead of the kernel log buffer
-f, —facility <list> restrict output to defined facilities
-H, —human human readable output
-k, —kernel display kernel messages
-L, —color[=<when>] colorize messages (auto, always or never)
-l, —level <list> restrict output to defined levels
-n, —console-level <level> set level of messages printed to console
-P, —nopager do not pipe output into a pager
-r, —raw print the raw message buffer
-S, —syslog force to use syslog(2) rather than /dev/kmsg
-s, —buffer-size <size> buffer size to query the kernel ring buffer
-u, —userspace display userspace messages
-w, —follow wait for new messages
-x, —decode decode facility and level to readable string
-d, —show-delta show time delta between printed messages
-e, —reltime show local time and time delta in readable format
-T, —ctime show human readable timestamp
-t, —notime don’t print messages timestamp
—time-format <format> show time stamp using format:
Suspending/resume will make ctime and iso timestamps inaccurate.

-h, —help display this help and exit
-V, —version output version information and exit

Supported log facilities:
kern — kernel messages
user — random user-level messages
mail — mail system
daemon — system daemons
auth — security/authorization messages
syslog — messages generated internally by syslogd
lpr — line printer subsystem
news — network news subsystem

Supported log levels (priorities):
emerg — system is unusable
alert — action must be taken immediately
crit — critical conditions
err — error conditions
warn — warning conditions
notice — normal but significant condition
info — informational
debug — debug-level messages


root@OrangePI:~# man dmesg
DMESG(1) User Commands DMESG(1)

dmesg — print or control the kernel ring buffer

dmesg [options]

dmesg —clear
dmesg —read-clear [options]
dmesg —console-level level
dmesg —console-on
dmesg —console-off

dmesg is used to examine or control the kernel ring buffer.

The default action is to read all messages from the kernel ring buffer.

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 after first printing its contents.

-D, —console-off
Disable the printing of messages to the console.

-d, —show-delta
Display the timestamp and the 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.

-e, —reltime
Display the local time and the delta in human-readable format.

-F, —file file
Read the messages from the given file.

-f, —facility list
Restrict output to the given (comma-separated) list of facili‐
ties. For example:

dmesg —facility=daemon

will print messages from system daemons only. For all supported
facilities see the —help output.

-H, —human
Enable human-readable output. See also —color, —reltime and

-h, —help
Display help text and exit.

-k, —kernel
Print kernel messages.

-L, —color[=when]
Colorize important messages (enabled by default). The optional
argument when can be auto, never or always. If the when argu‐
ment is omitted, it defaults to auto.

-l, —level list
Restrict output to the given (comma-separated) list of levels.
For example:

dmesg —level=err,warn

will print error and warning messages only. For all supported
levels see the —help output.

-n, —console-level level
Set the level at which printing of messages is done to the con‐
sole. The level is a level number or abbreviation of the level
name. For all supported levels see the —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 sys‐
logd(8) can still be used to control exactly where kernel mes‐
sages appear. When the -n option is used, dmesg will not print
or clear the kernel ring buffer.

-P, —nopager
Do not pipe output into a pager. A pager is enabled by default
for —human output.

-r, —raw
Print the raw message buffer, i.e. do not strip the log-level

Note that the real raw format depends on the method how dmesg(1)
reads kernel messages. The /dev/kmsg device uses a different
format than syslog(2). For backward compatibility, dmesg(1)
returns data always in the syslog(2) format. It is possible to
read the real raw data from /dev/kmsg by, for example, the com‐
mand ‘dd if=/dev/kmsg iflag=nonblock’.

-S, —syslog
Force dmesg to use the syslog(2) kernel interface to read kernel
messages. The default is to use /dev/kmsg rather than syslog(2)
since kernel 3.5.0.

-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.

Be aware that the timestamp could be inaccurate! The time
source used for the logs is not updated after system SUS‐

-t, —notime
Do not print kernel’s timestamps.

-u, —userspace
Print userspace messages.

-V, —version
Display version information and exit.

-w, —follow
Wait for new messages. This feature is supported only on sys‐
tems with a readable /dev/kmsg (since kernel 3.5.0).

-x, —decode
Decode facility and level (priority) numbers to human-readable

—time-format format
Print timestamps using the given format, which can be ctime,
reltime, delta or iso. The first three formats are aliases of
the time-format-specific options. The iso format is a dmesg
implementation of the ISO-8601 timestamp format. The purpose of
this format is to make the comparing of timestamps between two
systems, and any other parsing, easy. The definition of the iso
timestamp is: YYYY-MM-DD<T>HH:MM:SS,<microseconds><-+><timezone
offset from UTC>.

The iso format has the same issue as ctime: the time may be
inaccurate when a system is suspended and resumed.

Implicit coloring can be disabled by an empty file /etc/terminal-col‐
ors.d/dmesg.disable. See terminal-colors.d(5) for more details about
colorization configuration.

The logical color names supported by dmesg are:

subsys The message sub-system prefix (e.g. «ACPI:»).

time The message timestamp.

alert The text of the message with the alert log priority.

crit The text of the message with the critical log priority.

err The text of the message with the error log priority.

warn The text of the message with the warning log priority.

The text of the message that inform about segmentation fault.

syslogd(8) terminal-colors.d(5)

Karel Zak ⟨kzak@redhat.com⟩

dmesg was originally written by Theodore Ts’o ⟨tytso@athena.mit.edu⟩

The dmesg command is part of the util-linux package and is available
from Linux Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-

util-linux July 2012 DMESG(1)