Reading boot messages on the fly

Jay Cliburn jacliburn at bellsouth.net
Sun Oct 1 16:12:01 UTC 2006


I've been experimenting with different methods for reading messages that scroll 
by rapidly during boot.  Several days ago on fedora-list, Dave Jones advised 
someone to use boot_delay=500 on the kernel command line to introduce a delay 
between boot messages.  I tried this, and it works really well to a point, 
however once the kernel frees init memory, something happens and the scroll 
speed returns to normal (which is very, very fast).

powernow-k8:    0 : fid 0xa (1800 MHz), vid 0x6
powernow-k8:    1 : fid 0x2 (1000 MHz), vid 0x12
ACPI: (supports S0 S3 S4 S5)
Freeing unused kernel memory: 212k freed    <-------- Last "slow" message
Losing some ticks... checking if CPU frequency changed.
Write protecting the kernel read-only data: 477k
input: AT Translated Set 2 keyboard as /class/input/input0
USB Universal Host Controller Interface driver v3.0

I'm most interested in seeing which modules are loaded by initrd, and when using 
boot_delay these are printed _after_ the transition to high speed message 
printing.  (Moreover, the lines "Loading module foo.ko" don't even show up in 
dmesg.)  Things improve a bit if I add vga=791 or vga=794 to the kernel command 
line, which results in more than 25 vertical lines per page, but the "loading 
module" lines still scroll off too quickly.

What are some methods you use for viewing boot messages?  (assume the system is 
broken and you can't login to it)

Thanks,
Jay




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