Because the logger is introduced to output the kdump logs, need to
add a documentation for this change and describe how to use it.
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
kexec-kdump-howto.txt | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt
index 7491a7d5b329..5f57a8428e4f 100644
@@ -885,3 +885,38 @@ Debugging Tips
minicom -C /tmp/console-logs
Now minicom should be logging serial console in file console-logs.
+- Using the logger to output kdump log messages
+ Currently, kdump messages are printed with the 'echo' command or redirect
+ to console, and which does not support to output kdump messages according
+ to the log level.
+ That is not convenient to debug kdump issues, we usually need to capture
+ additional debugging information via the modification of the options or the
+ scripts like kdumpctl, mkdumprd, etc. Because there is no complete debugging
+ messages, which could waste valuable time.
+ To cope with this challenging, we introduce the logger to output the kdump
+ messages according to the log level, and provide a chance to save logs to
+ the journald if the journald service is available, and then dump all logs
+ to a file, otherwise dump the logs with the dmesg to a file.
+ Logging is controlled by following global variables:
+ - @var kdump_stdloglvl - logging level to standard error (console output)
+ - @var kdump_sysloglvl - logging level to syslog (by logger command)
+ - @var kdump_kmsgloglvl - logging level to /dev/kmsg (only for boot-time)
+ If any of the variables is not set, this function set it to default:
+ - @var kdump_stdloglvl=4 (info)
+ - @var kdump_sysloglvl=4 (info)
+ - @var kdump_kmsgloglvl=0 (no logging)
+ Logging levels: fatal(1),error(2),warn(3),info(4),debug(5),trace(6)
+ We can easily configure the above variables in the /etc/sysconfig/kdump. For
+ The above configurations indicate that kdump messages will be printed to the
+ console and journald if the journald service is enabled.