7:38 a.m.
Let's remove some redundant descriptions in the usage
documentation of the logger, and make it clear.
Signed-off-by: Lianbo Jiang <lijiang(a)redhat.com>
---
kexec-kdump-howto.txt | 81 ++++++++++++++++++++++++++++---------------
1 file changed, 53 insertions(+), 28 deletions(-)
diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt
index 5f57a8428e4f..46ca99b994c0 100644
--- a/kexec-kdump-howto.txt
+++ b/kexec-kdump-howto.txt
@@ -888,35 +888,60 @@ Debugging Tips
- 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)
+ You can configure the kdump log level in the /etc/sysconfig/kdump.
+ For example:
+
+ kdump_sysloglvl=4
+ kdump_stdloglvl=4
+
+ The above configurations indicate that kdump messages will be printed to the
+ console and journald if the journald service is enabled, and the log level is
+ set to 4(info). This is also the current default log level.
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
- example:
- kdump_sysloglvl=5
- kdump_stdloglvl=5
+ The FATAL level designates very severe error events that will presumably lead
+ the application to abort. Currently, the FATAL level is not used.
- The above configurations indicate that kdump messages will be printed to the
- console and journald if the journald service is enabled.
+ The ERROR level designates error events that might still allow the application
+ to continue running.
+
+ The WARN level designates potentially harmful situations.
+
+ The INFO level designates informational messages that highlight the progress
+ of the application at coarse-grained level.
+
+ The DEBUG level designates fine-grained informational events that are most
+ useful to debug an application.
+
+ The TRACE level designates finer-grained informational events than the DEBUG.
+ Currently, the TRACE level is not used.
+
+ At present, the logger works in both the first kernel(kdump service debugging)
+ and the second kernel. But the TRACE and FATAL level are not used(as mentioned
+ above), which are only kept here as a syslog conversion.
+
+ In the first kernel, you can find the historical logs with the journalctl
+ command and check kdump service debugging information. In addition, the
+ 'kexec -d' debugging messages are also saved to /var/log/kdump.log in the
+ first kernel. For example:
+
+ [root@ibm-z-109 ~]# ls -al /var/log/kdump.log
+ -rw-r--r--. 1 root root 63238 Oct 28 06:40 /var/log/kdump.log
+
+ In the second kernel, put the kexec-dmesg.log to a same directory with the
+ vmcore, the log file includes the debugging messages like dmesg and journald
+ logs. For example:
+
+ [root@ibm-z-109 ~]# ls -al /var/crash/127.0.0.1-2020-10-28-02\:01\:23/
+ drwxr-xr-x. 2 root root 67 Oct 28 02:02 .
+ drwxr-xr-x. 6 root root 154 Oct 28 02:01 ..
+ -rw-r--r--. 1 root root 21164 Oct 28 02:01 kexec-dmesg.log
+ -rw-------. 1 root root 74238698 Oct 28 02:01 vmcore
+ -rw-r--r--. 1 root root 17532 Oct 28 02:01 vmcore-dmesg.txt
+
+ If you want to get more debugging information in the second kernel, you can add
+ the 'rd.debug' option to the KDUMP_COMMANDLINE_APPEND in the
/etc/sysconfig/kdump,
+ and then reload them in order to make the changes take effect.
+
+ For more details, please refer to the /etc/sysconfig/kdump.
--
2.17.1