Kernel debugging
A wide range of different kernel options can help in debugging what is going on within the kernel. Following is a list of some of the more common ones that can be useful for discovering new things about how the kernel works, or help find potential problems within the current kernel source code.
Kernel log timestamps
The kernel outputs a wide range of messages to its log file. These messages can be seen by looking at the system log file (usually located in /var/log/messages), or by running the dmesg command.
Sometimes it is useful to see exactly when those messages were
created. dmesg, however, does not
put any timestamps on the events it shows, and the time resolution of
/var/log/messages
is only to the
nearest second. You can configure the kernel to assign each message a
timestamp that is accurate down to the smallest measurable kernel time
value (usually in the microsecond range.)
To enable timestamp options on kernel messages:
Kernel hacking [*] Show timing information on printks
Magic SysRq keys
The SysRq
key on the keyboard
can be used to control the kernel in a number of different ways while
the kernel is running, or after it has crashed.
To enable this option:
Kernel hacking [*] Magic SysRq key
For a full description of the different actions that can be triggered by this option, please see the file Documentation/sysrq.txt in the kernel source tree.
Debug Filesystem
A RAM-based filesystem can be used to output a lot of different debugging information. This filesystem ...
Get Linux Kernel in a Nutshell now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.