Re: [gentoo-user] Separate /usr partition

[karl@aspodata.se]

Peter:
> I'm thinking of separating /usr onto its own partition so that I can have it 
> mounted read-only except while updating it. I'd prefer not to have to make an 
> init thingy, not having needed one up to now. Besides, some machines have 
> things like early-ucode or amd-uc.
> 
> I've found a few guides on the Web, but I'm still confused. Is there a simple 
> guide to doing this? I know of at least one subscriber here who's done it.  :)

I'm using separate /usr, it was the default historically and I just
continued useing it, partly because it is unconvenient to repartion
long running remote systems.

There are a few things to look out for.
If you are not using initrd/initramfs, you need all drivers to access 
/ to be compiled in. Easiest is if don't use devices with dynamic
minors. Once / is mounted you have all drivers available
in /lib/modules, then the next possible hurdle is to survive long 
enought till /usr is mounted. For that you a suitable mount command 
which does not depend on /usr, i.e. it or any programs previous it
in the bootup cannot depend on libs in /usr. The easiest way to
accomplish that is to use busybox.

It is also possible to use sys-fs/static-dev, if you want to opt
to not use udev.

Regards,
/Karl Hammar