Getting started with mdev

[Rob Landley]

On Thursday 14 December 2006 4:58 pm, Trevor Harmon wrote:
> > IIRC there were a few files you should add to your static /dev:  
> > console,
> > null,
> 
> Hmm... /dev/console is the only one I needed to boot and run BusyBox.

/dev/console is the only one used by the kernel _before_ execing init.  (In 
the 2.6.19 kernel, it's init/main.c line 768.)

> > <but i can't remember the rest>
> 
> How would I find out what the rest are? Given that /dev is such an  
> important and fundamental part of Linux, it seems like this would be  
> written down somewhere.

lanana.org lists all known devices.

> > than you need to add /sys to your filsystem, and mount the sysfs there
> >
> >     mount -t sysfs none /sys
> >
> > once that is done you can run mdev in scan mode to populate /dev
> >
> >     mdev -s
> >
> > that should be it.
> 
> That worked; thanks! I noticed that mdev created a lot of "standard"  
> entries in /dev, including null. I assume that means I don't have to  
> worry about manually creating them?

Yup.  There are entries for them under /sys, so mdev makes 'em.

> Also, what's the standard practice of having the above commands run  
> on every boot? Do I simply dump them into /etc/rc.sh?

Yup.  Personally, I mount a tmpfs on /dev so you don't have to worry about 
debris between boots.  (If mdev sees that a device already exists, it'll skip 
trying to create it, but mdev -s won't delete anything that's already there.  
Since tmpfs starts empty, they complement each other nicely.)

Rob
-- 
"Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away." - Antoine de Saint-Exupery