Lustre 1.6 Operations Manual

To turn off network logging with changing existing flags:
sysctl -w lnet.debug=-net
The various options available to print to kernel debug logs are listed in
lnet/include/libcfs/libcfs.h
23.2.3 The lctl Tool
Lustre’s source code includes debug messages which are very useful for
troubleshooting. As described above, debug messages are subdivided into a number
of subsystems and types. This subdivision allows messages to be filtered, so that
only messages of interest to the user are displayed. The lctl tool is useful to enable
this filtering and manipulate the logs to extract the useful information from it. Use
lctl to obtain the necessary debug messages:
1. To obtain a list of all the types and subsystems:
lctl > debug_list
2. To filter the debug log:
lctl > filter
Note – When lctl filters, it removes unwanted lines from the displayed output.
This does not affect the contents of the debug log in the kernel's memory. As a result,
you can print the log many times with different filtering levels without worrying
about losing data.
3. To show debug messages belonging to certain subsystem or type:
lctl > show
debug_kernel pulls the data from the kernel logs, filters it appropriately, and
displays or saves it as per the specified options
lctl > debug_kernel [output filename]
If the debugging is being done on User Mode Linux (UML), it might be useful to
save the logs on the host machine so that they can be used at a later time.
Chapter 23 Lustre Debugging 23-7