Description of kernel.printk values
Sysctl settings are documented in Documentation/sysctl/*.txt
in the kernel source tree. On Debian, install linux-doc
to have the documentation in usr/share/doc/linux-doc-*/Documentation/
(most distributions have a similar package). From Documentation/sysctl/kernel.txt
:
The four values in
printk
denote:console_loglevel
,default_message_loglevel
,minimum_console_loglevel
anddefault_console_loglevel
respectively.These values influence
printk()
behavior when printing or logging error messages. Seeman 2 syslog
for more info on the different loglevels.
console_loglevel
: messages with a higher priority than this will be printed to the consoledefault_message_loglevel
: messages without an explicit priority will be printed with this priorityminimum_console_loglevel
: minimum (highest) value to which console_loglevel can be setdefault_console_loglevel
: default value forconsole_loglevel
I don't find any clear prose explanation of what default_console_loglevel
is used for. In the Linux kernel source, the kernel.printk
sysctl sets console_printk
. The default_console_loglevel
field doesn't seem to be used anywhere.
Description of kernel.printk
values
- "0" → Emergency messages, system is about to crash or is unstable pr_emerg
- "1" → Something bad happened and action must be taken immediately pr_alert
- "2" → A critical condition occurred like a serious hardware/software failure pr_crit
- "3" → An error condition, often used by drivers to indicate difficulties with the hardware pr_err
- "4" → A warning, meaning nothing serious by itself but might indicate problems pr_warning
- "5" → Nothing serious, but notably nevertheless. Often used to report security events. pr_notice
- "6" → Informational message e.g. startup information at driver initialization pr_info
- "7" → Debug messages pr_debug, pr_devel if DEBUG is defined
- KERN_DEFAULT "d" The default kernel loglevel
- KERN_CONT "" "continued" line of log printout (only done after a line that had no enclosing)