Re: [gentoo-user] /dev/sda* missing at boot

[Alan McKinnon <alan.mckinnon@gmail.com>]

On Thu, 8 Sep 2011 19:34:56 -0400
Canek Peláez Valdés <caneko@gmail.com> wrote:

> > You don't need every possible thing that udev could ever run to be
> > avialable on /, just the things that are essential. That is quite a
> > small list subset of the full list of all possible devices:
> >
> > All HID devices
> > All console devices
> > All code to access and read file systems
> > Everything that can be used in place of a physical keyboard (serial,
> > console over ethernet)
> >
> > That looks like it might be a large amount of disk space, but
> > in fact it isn't. This very mail is being typed on a binary distro
> > (Ubuntu):
> >
> > The bluez package is 1.6M.
> > /lib alone is 331M, I use a fraction of it but it is still there.
> > /lib/modules contains two kernel versions of 136M each.  
> 
> Again, it is not bounded. Today is bluez, tomorrow we don't know.
> That's the point of udev, really.

You're still not getting it.

Just because it appears convenient to make udev unbounded does not mean
that all possible code on the machine has to be accessible to udev.
Or that udev will potentially run any arbitrary code you might have.
Or put another way, udev might be able to run anything, like say
lauching KDE, but the simple truth is that it won't in any reasonable
scenario. Therefore you do not need to support or entertain that
possibility. The truth is that a very small portion of the total code
on the machine needs to be accessible to udev and all of it (including
all foreseeable code) fits into a traditional / quite nicely.

There is no upper limit on the size of /, you simply make it as large as
you need and put everything supported in there.

Once again, and this is very important, the only things that are
absolutely required to be in / is all the code that must run
before /usr is mounted. That list of things is very small, and if the
user or the distro happens to cock it up, then the user or distro must
fix it. 

Why is this apparently so hard to understand? The solution seems
blindingly obvious:

Any code launched by udev must be available on the same partition as /.
However the system is rigged, that one condition must be satisfied. And
consider who is setting this up:

- root, who presumably knows what they are doing
- distro devs, who also know what they are doing

Or are the udev devs seriously contemplating allowing udev hooks so
that any arbitrary user can launch any arbitrary code that might
arbitrarily be anywhere?

I still maintain this "fix" is for a problem that does not exist.


-- 
Alan McKinnnon
alan.mckinnon@gmail.com