How to stop kernel messages from flooding my console?

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本文介绍如何通过修改CentOS系统的/sysctl.conf文件来调整内核的日志级别，特别是kernel.printk参数的设置。文章还提供了如何使用sysctl命令在运行时更改这些设置的方法，并解释了不同日志级别所代表的意义。

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I suggest you alter your /etc/sysctl.conf. Specifcally, you want to tweak the kernel.printk line.

# Uncomment the following to stop low-level messages on console
kernel.printk = 3 4 1 3

I am not sure what the centos default settings are, but I seems likely that have things set more verbose then you need.

Also do see the shorewall section on logging. You don't have to use the LOG target for logging, you can use other tools, or adjust the log severity, and tweak things to control where you messages go.

To set the values at runtime, use sysctl. (I suppose one can write to /proc/sys/kernel/printkdirectly too and apparently you can also use dmesg -n CUR as described here)

Display:

# sysctl kernel.printk
kernel.printk = 2       4       1       7

The separators in the output are single tabs, btw.

Set. Here the separators are just spaces. Works as well.

# sysctl -w kernel.printk="2 4 1 7"
kernel.printk = 2 4 1 7
# sysctl kernel.printk
kernel.printk = 2       4       1       7

See man sysctl - "configure kernel parameters at runtime" for more.

Reminder of the severity levels and the four values of kernel.printk given by Brian above:

CUR = current severity level; only messages more important than this level are printed
DEF = default severity level assigned to messages with no level
MIN = minimum allowable CUR
BTDEF = boot-time default CUR

On my CentOS: 7 4 1 7

                     CUR  DEF  MIN  BTDEF
0 - emergency        x              x                        
1 - alert            x         x    x
2 - critical         x              x
3 - error            x              x
4 - warning          x    x         x
5 - notice           x              x
6 - informational    V              V
7 - debug

This is too noisy, I just want critical and up (no errors). Unlabeled messages should be regarded as warning, so DEF is good:

                     CUR  DEF  MIN  BTDEF
0 - emergency        x              x                        
1 - alert            x         x    x
2 - critical         x              x
3 - error            V              V
4 - warning               x         
5 - notice                           
6 - informational                   
7 - debug

Set to: 3 4 1 3