rawhide report: 20101019 changes

[Lennart Poettering]

On Tue, 19.10.10 14:43, Paul Howarth (paul at city-fan.org) wrote:

> 
> On 19/10/10 14:11, Rawhide Report wrote:
> > anaconda-15.3-1.fc15
> > --------------------
> > * Mon Oct 18 2010 Chris Lumens<clumens at redhat.com>  - 15.3-1
> > - Don't recommend /usr as a mount point anymore (#643640). (clumens)
> 
> This despite the FHS says (right at the top of Chapter 3, the Root 
> Filesystem):
> 
>    /usr, /opt, and /var are designed such that they may be located on other
>    partitions or filesystems.
> 
> Do we *really* want to head this way, ignoring bugs resulting from 
> having /usr on a different partition such as 
> http://bugzilla.redhat.com/#626007, which is what led to this?

During my experimenting with readahead I noticed how many files are
actually accessed during early boot that are in /usr. It's a lot more
than udisks. It's also everything related to i18n, and a lot other
stuff. Already if you run things this way you'll thus have serious
functionality limitations. And I see little value in making this work
again.

Note that many other distributions gave up on seperate /usr already (for
example, Gentoo do this, and even refers to Fedora that it wasn't
supported here, which is technically true, but so far not officially).

I think the whole approach of seperate /usr (which iiuc is done to make
/usr r/o during normal runtime) is wrong anyway. It aims too low. If
people want to make something r/o it should be the entirety of /
read-only, and we probably should make that the default even
eventually. That'd be a worthy goal. However, right now there's still a
handful of programs that write around in /etc during runtime, such as
NM, and stuff related to /etc/nologin, /forcefsck, /etc/mtab,
/etc/securetty and similar files. (a couple of which will hopefully go
away soonishly. i.e. /etc/nologin is being migrated to /var/run/nologin
now, and /forcefsck has a kernel cmdline option "forcefsck" which is a
lot more useful. util-linux-ng is working on getting rid of /etc/mtab
and already works mostly when you link it to /proc/mounts. For the
securetty hacks I sent a patch last week to PAM.)

Debian in fact has been making great progress to make their OS work with
read-only root by default: http://wiki.debian.org/ReadonlyRoot

Also note that a number of commercial unixes symlink / and /usr these
days, going one step further even.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.