Re: How hard is it to move separate /usr to / partition? - WAS Re: [gentoo-user] Optional /usr merge in Gentoo

[Paul Hartman <paul.hartman+gentoo@gmail.com>]

On Fri, Aug 16, 2013 at 10:04 AM, Tanstaafl <tanstaafl@libertytrek.org> wrote:
>> And really, maybe you could try an initramfs? It will be much more
>> easy than any juggle of filesystems.
>
>
> I always compile my kernels manually, by choice - so, no desire to use
> genkernel or dracut.
>
> How would I then create one? I am *not* a programmer, just a reasonably
> competent general sys admin.
>
> Is there a 'generic' one that I can use? Or is there a separate tool that
> will create one based on my system profile (or whatever)?

I think dracut is actually exactly the tool you are looking for. It
does not have anything to do with building your kernel, its sole job
in life is to generate an initramfs built to your specifications. It
contains sane defaults but you can tweak it to include or exclude
things as you see fit. I build my kernel by hand and then run dracut
afterward to generate the initramfs.img.

I believe mounting /usr is enabled by default in dracut. I would
recommend checking out the documentation and seeing all the different
options and modules that are available so you can customize it to
match your needs. For example you may want to have it import your LVM
configuration, assemble a RAID, use the reiserfs or btrfs filesystem,
etc.

Once it generates the initramfs it's as simple as adding a line to
your grub config and off you go. If it doesn't work right away you can
just comment out that line and boot without it, for now, while your
existing setup is still valid. (It took me a few reboots to find the
right combination of options.) Then someday if separate /usr is no
longer allowed without an initramfs, you'll be prepared for it.

I always regenerate my initramfs using dracut after every time i build
a new kernel, but I'm not sure if that's truly necessary. Honestly
it's all still a bit of a black box to me.