Sometimes mysqld or Linux systems, or other processes running on the system, it will be some strange problems, such as suddenly hung up, such as a sudden reboot and so on. Can not find the problem in the software, then we should suspect a hardware problem, or kernel, then we can use dmesg to see:
dmesg - print or control the kernel ring buffer
dmesg [-c] [-r] [-n level] [-s bufsize]
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
and mail the boot.messages file to whoever can debug their problem.
-c Clear the ring buffer contents after printing.
-r Print the raw message buffer, i.e., do not strip the log level prefixes.
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.
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.
Direct execution: dmesg or dmesg> dmg.txt Hardware information can be obtained and kernel startup.