Sunday, March 6, 2011

detailed kernel bootup debug messages

Users like me prefer as much debugging output in applications as possible because this makes performance and stability issues easy to understand. This also allows one to see what all is going on behind the scenes for crash debugging. A few amendments can be added to the kernel boot parameters of a Linux kernel to allow for detailed messages and verbose output:

By modifying the 'kernel' line in grub or editing the relevant boot file under /boot/grub and adding the following[in bold]:

kernel /boot/vmlinuz26 root=/dev/disk/by-label/Arch ro debug ignore_loglevel log_buf_len=10M print_fatal_signals=1 LOGLEVEL=8 earlyprintk=vga,keep sched_debug
heavy debugging can be easily activated.

debug = activates internal debugging.
ignore_loglevel =  ignores any sort of log level and maximizes debug output.
log_buf_len = increases the log buffer length to 10 MiB
print_fatal_signals = print any fatal signals.
LOGLEVEL = enables level 8 logging.
earlyprintk = enables early printing of messages to the vga screen
,keep = keeps the messages on for longer.
sched_debug = Enables verbose scheduler debug messages.


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