What do the values in printk kernel parameter mean in linux?
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$ sysctl kernel.printk kernel.printk = 7 4 1 7
The text below says syslog but, most Linux systems now use rsyslog. The man page for syslog may not exist.
printk: The four values in printk denote: console_loglevel, default_message_loglevel, minimum_console_loglevel and default_console_loglevel respectively. These values influence printk() behavior when printing or logging error messages. See 'man 2 syslog' for more info on the different loglevels. - console_loglevel: messages with a higher priority than this will be printed to the console - default_message_loglevel: messages without an explicit priority will be printed with this priority
- minimum_console_loglevel: minimum (highest) value to which console_loglevel can be set - default_console_loglevel: default value for console_loglevel
In the example this equates to the following, which is the default setting on redhat.
console_loglevel = 7
default_message_loglevel = 4
minimum_console_loglevel = 1
default_console_loglevel = 7The numbers relate to the following:
Supported log levels (priorities): 0 emerg - system is unusable 1 alert - action must be taken immediately 2 crit - critical conditions 3 err - error conditions 4 warn - warning conditions 5 notice - normal but significant condition 6 info - informational 7 debug - debug-level messages
Redhat descriptions of the log levels.
The log-level values break down in this order: 0 — Kernel emergency. The system is unusable. 1 — Kernel alert. Action must be taken immediately. 2 — Condition of the kernel is considered critical. 3 — General kernel error condition. 4 — General kernel warning condition. 5 — Kernel notice of a normal but significant condition. 6 — Kernel informational message. 7 — Kernel debug-level messages.
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