Linux 核心紀錄檔——dmesg

有時Linux系統或者系統上執行的mysqld或者其它進程，會發生一些莫名其妙的問題，比如突然掛掉了，比如突然重新啟動等等。在軟體上找不到問題所在，此時我們應該懷疑硬體或者核心的問題，此時我們就可以使用 dmesg 來檢視：

NAME
      dmesg - print or control the kernel ring buffer

SYNOPSIS
      dmesg [-c] [-r] [-n level] [-s bufsize]

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

      The  program  helps users to print out their bootup messages.  Instead of copying the messages by hand, the user need
      only:
              dmesg > boot.messages
      and mail the boot.messages file to whoever can debug their problem.

OPTIONS
      -c    Clear the ring buffer contents after printing.

      -r    Print the raw message buffer, i.e., don’t strip the log level prefixes.

      -s bufsize
              Use a buffer of size bufsize 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.

      -n level
              Set the level at which logging of messages is done to the console.  For example, -n 1 prevents  all  messages,
              except 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.

              When both options are used, only the last option on the command line will have an effect.

SEE ALSO
      syslogd(8)

直接執行：dmesg 或者 dmesg > dmg.txt 就可以獲得硬體資訊和核心啟動時的資訊。

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