Adding Linux kernel command line parameters

Question

I would like to increase the size of the vmalloc region from the default value, and pass vmalloc= as a command line parameter while booting. I am booting a uImage. In which file do I need to add the new vmalloc command line parameter so that it is known to the kernel at boot time?

Answer 1

If you are using Lilo as a bootloader, edit the relevant part of /etc/lilo.conf to look something like this:

image=/vmlinuz
        label=Linux
        append="vmalloc=foo"
        initrd=/initrd.img
        read-only
        root=/dev/sda1

Then, run lilo(8) to reinstall the bootloader with the new parameter.

Of course, I cannot tell you exactly how your /etc/lilo.conf should look, since this depends on the overall configuration of your system, but the interesting line is the one that reads append=. You can use such a line to pass any desired boot parameter to the kernel.

(If you prefer Grub as a bootloader, this is fine, but someone else must answer your question in that case, for I do not happen to use Grub.)

If you just want to try your vmalloc=foo for one boot, rather than to install it persistently, you can simply type vmalloc=foo or (assuming that you have labeled your kernel as "Linux") Linux vmalloc=foo at the boot prompt. The only trick is getting to the boot prompt, which your bootloader may be configured to suppress. Try holding down the shift key at boot time, which may prevent the bootloader from suppressing the prompt.