Re: understanding /proc/cmdline

[Jon Masters <jonmasters@xxxxxxxxx>]

On Sat, 2 Oct 2004 23:05:26 +0900, aq <aquynh@xxxxxxxxx> wrote:

> Anybody please tell me which file in kernel source code to generate
> /proc/cmdline file?

jcm@perihelion:~/ppc64/linux-2.6.8.1/fs/proc$ grep -r cmd .
./proc_misc.c:static int cmdline_read_proc(char *page, char **start, off_t off,
./proc_misc.c:          {"cmdline",     cmdline_read_proc},
<and some other stuff>

In proc_misc.c we have a read function registered for that proc entry
called cmdline_read_proc which, as you can see, uses
saved_command_line.

saved_command_line is setup during kernel entry in head.S and setup.c,
although this varies according to the architecture you are using.

> And this is the content of my /proc/cmdline
> 
> ~$ cat /proc/cmdline
> auto BOOT_IMAGE=Linux2681 ro root=303

> Please tell me what "root=303" means?

It's a device upon which your root filesystem resides - e.g. hda3 (see
the device entry numbers in /dev where you can see the 303 represents
a combination of major and minor number of the device).

Jon.

--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive:       http://mail.nl.linux.org/kernelnewbies/
FAQ:           http://kernelnewbies.org/faq/