On Mon, Jul 5, 2010 at 12:11 PM, Willie Wong <ww...@math.princeton.edu> wrote: > On Mon, Jul 05, 2010 at 09:16:14AM -0700, Mark Knecht wrote: >> I'm trying to capture the full boot log when booting from the Gentoo >> install CD but it seems the buffer isn't deep enough to get the whole >> thing. Is there by chance a command line option that will increase the >> depth of what's captured by dmesg so that I can get all the way back >> to the beginning? > > pass the following parameter to the kernel on GRUB/LILO: > > log_buf_len=n > > where n is a power of two. By default it is 16384. You can change it > to 131072 (= 2^17) to get a much larger kernel log ring buffer. If you > put in something that is not a power of two, the kernel will ignore > the option. > > You may also have to pass an additional parameter to dmesg to read the > early messages: look at 'man dmesg' and the -s flag. > > Cheers, > > W > --
Hi Willie, Thanks for the ideas. I've been trying them but so far no luck. In my normal booting kernel (on the system hard drive) I did push the length up to 18. With that setting dmesg prints all the way back to the beginning. However booting the Live CD I hit F1, it shows the kernels, so I type gentoo log_buf_len=18 and then boot, but dmesg never goes back to the beginning. I've also tried dmesg -s 300000 but still the results are cut off somewhere down in the stack and I never see the first part of the buffer. I'm looking at this page for some info: http://www.kernel.org/pub/linux/kernel/people/gregkh/lkn/lkn_pdf/ch09.pdf Reading about log_buf_len I also see earlyprintk and time options. I tried them at the Live CD command line but it didn't change what I'm getting in dmesg like it did on my regular kernel. I'll continue to study. Thanks, Mark
