Re: [gentoo-user] Re: Beta test Gentoo with mdev instead of udev; version 3

[Pandu Poluan <pandu@poluan.info>]

On Tue, Jan 3, 2012 at 20:13, Nicolas Sebrecht <nsebrecht@piing.fr> wrote:
> The 03/01/12, Pandu Poluan wrote:
>
>>    But I can see a use case for mdev completely replacing udev: servers and
>>    virtual machines.
>>
>>    Servers, especially production ones, have a hardware change only once in
>>    every two blue moons. They don't need all the bells and whistles of udev.
>>
>>    Even more so when you've gone the virtualized route.
>>
>>    Since servers are arguably where Linux shines the most, mdev should be
>>    seriously considered as a udev replacement.
>
> But servers have enough ressources to run udev and any required
> initramfs to mount /usr.
>

No, no, no, you got it the wrong way around.

It's not udev *per se* that I -- as a server admin -- want to get rid of.

It's the initramfs.

And I also want to put /usr in a separate partition.

The problem is that, judging from where udev is going in upstream, we
will be forced to use initramfs, or put /usr in /

By migrating from udev to mdev, I am no longer forced to do either.

> So, the question is where engineering should go:
>
> - mdev and manually manage /dev devices if nedded
>
> or
>
> - rely on initramfs to mount /usr.
>

As a SysAdmin, I'd prever the 1st one, thank you.

Adding hardware to server is a MAJOR event, something worthy of
sacrificing some goats and lambs to appease the Information Gods and
Goddesses.

And after the new shiny thing gets installed physically, it will be
followed up -- with 109% certainty -- with some configuration in the
OS.

> As initramfs is a prooven working solution, all distributions I know use
> it either by default or if needed.
>

Then again, using initramfs is yet-another-component waiting to break.

Knowing Murphy's Law, it will one day fuck up everything.

> Also, I think the coming problem you will be face with in the mdev way
> is the move of binaries from /bin to /usr/bin and so.
>

Again, on a server, this will be a one-time affair.

I can always bind-mount the /usr of / under /mnt, letting the "/usr"
get overlaid by the /usr partition. If there's a piece of hardware
that needs a piece of binary inside /usr, I'll just cp that binary
into /mnt/usr/whatever to appease that piece of hardware.

Rgds,
-- 
FdS Pandu E Poluan
~ IT Optimizer ~

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