Linux 在启动期间更改默认控制台日志级别
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Change default console loglevel during boot up
提问by Ahmed A
I setup a CentOS 6.3 setup, on which the console loglevel is set to 4, and default log level is set to 4. I know I can change the default console log level using the following steps:
我设置了 CentOS 6.3 设置，其中控制台日志级别设置为 4，默认日志级别设置为 4。我知道我可以使用以下步骤更改默认控制台日志级别：
cat /proc/sys/kernel/printk
4 4 1 7
echo 5 > /proc/sys/kernel/printk
cat /proc/sys/kernel/printk
5 4 1 7
However, upon reboot, the console log level reverts back to the original value. Do I need to recompile the kernel, or is there a way I can get the changed value to be persistent across reboot.
但是，重新启动后，控制台日志级别将恢复为原始值。我是否需要重新编译内核，或者有什么方法可以使更改后的值在重新启动后保持不变。
采纳答案by sawdust
Do I need to recompile the kernel,
我需要重新编译内核吗，
No.
不。
or is there a way I can get the changed value to be persistent across reboot.
或者有什么方法可以使更改后的值在重新启动时保持不变。
Yes.
Use the kernel command line parameter loglevel:
是的。
使用内核命令行参数loglevel：
loglevel= All Kernel Messages with a loglevel smaller than the
console loglevel will be printed to the console. It can
also be changed with klogd or other programs. The
loglevels are defined as follows:
0 (KERN_EMERG) system is unusable
1 (KERN_ALERT) action must be taken immediately
2 (KERN_CRIT) critical conditions
3 (KERN_ERR) error conditions
4 (KERN_WARNING) warning conditions
5 (KERN_NOTICE) normal but significant condition
6 (KERN_INFO) informational
7 (KERN_DEBUG) debug-level messages
The entire list of parameters possible on the kernel command line are in the Linux/Documentation/kernel-parameters.txtfile in the source tree.
内核命令行上可能出现的整个参数列表都在Linux/Documentation/kernel-parameters.txt源代码树的文件中。
Depending on your bootloader (e.g. Grub or U-Boot), you will have to edit text to add this new parameter to the command line. Use cat /proc/cmdlineto view the kernel command line used for the previous boot.
根据您的引导加载程序（例如 Grub 或 U-Boot），您必须编辑文本以将此新参数添加到命令行。使用cat /proc/cmdline查看使用以前的引导内核的命令行。
Addendum
附录
To display everything, the number supplied for the loglevel parameter would have be be greater than KERN_DEBUG.
That is, you would have to specify loglevel=8.
Or simply use the ignore_loglevelparameter to display all kernel messages.
要显示所有内容，为 loglevel 参数提供的数字必须大于 KERN_DEBUG。
也就是说，您必须指定loglevel=8.
或者简单地使用该ignore_loglevel参数来显示所有内核消息。
