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Old 10-19-2010, 01:43 PM
Paul Howarth
 
Default rawhide report: 20101019 changes

On 19/10/10 14:11, Rawhide Report wrote:
> anaconda-15.3-1.fc15
> --------------------
> * Mon Oct 18 2010 Chris Lumens<clumens@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?

Paul.
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Old 10-19-2010, 01:56 PM
Matthew Garrett
 
Default rawhide report: 20101019 changes

On Tue, Oct 19, 2010 at 02:43:33PM +0100, Paul Howarth wrote:

> 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?

What's the benefit in having /usr or /opt as separate filesystems?

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Old 10-19-2010, 01:57 PM
Peter Lemenkov
 
Default rawhide report: 20101019 changes

2010/10/19 Paul Howarth <paul@city-fan.org>:

> http://bugzilla.redhat.com/#626007

Comments are worth reading, I'm sure.

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Old 10-19-2010, 02:01 PM
Chris Lumens
 
Default rawhide report: 20101019 changes

> 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.

Neat.

> 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?

If you read the entire commit message, you'll see:

commit 1ae53648c9e3460eb63837b4c20bc860018979f0
Author: Chris Lumens <clumens@redhat.com>
Date: Mon Oct 18 11:09:36 2010 -0400

Don't recommend /usr as a mount point anymore (#643640).

You can still use it if you really want (by inputting it manually), but
the Installation Guide recommends against its use.

In other words, you can still use any mount point you want.

- Chris
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Old 10-19-2010, 02:08 PM
Paul Howarth
 
Default rawhide report: 20101019 changes

On 19/10/10 15:01, Chris Lumens wrote:
>> 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.
>
> Neat.
>
>> 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?
>
> If you read the entire commit message, you'll see:
>
> commit 1ae53648c9e3460eb63837b4c20bc860018979f0
> Author: Chris Lumens<clumens@redhat.com>
> Date: Mon Oct 18 11:09:36 2010 -0400
>
> Don't recommend /usr as a mount point anymore (#643640).
>
> You can still use it if you really want (by inputting it manually), but
> the Installation Guide recommends against its use.
>
> In other words, you can still use any mount point you want.

I did read that, which is why I added the reference to Bug #626007
(trimmed from your reply), which is where this change originated from;
that is a bug that is being ignored on the basis that /usr is on a
separate partition.

I'm fine with setting up my own partitioning arrangements but I'd rather
not see a system that doesn't work once installed this way.

Paul.
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Old 10-19-2010, 02:24 PM
Chris Adams
 
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Once upon a time, Matthew Garrett <mjg59@srcf.ucam.org> said:
> On Tue, Oct 19, 2010 at 02:43:33PM +0100, Paul Howarth wrote:
> > 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?
>
> What's the benefit in having /usr or /opt as separate filesystems?

A smaller / that is written to less often is less susceptible to errors.
If you don't allocate enough space for / up front, you can move /usr and
/opt to separate filesystems later. /opt can be completely
unpredictable in space usage, due to vendor RPMs dumping stuff in /opt
(see Dell's OMSA, that puts everything, including logs, under /opt).

When disk was expensive, /usr was often the biggest consumer of space,
so it would be shared across the network, but that's not a big issue
anymore (and RPM doesn't really support shared /usr IIRC).

I personally don't use a separate /usr on desktops, only on servers. On
my servers, /usr is mounted read-only, as an extra protection against
accidental (or even intentional) screw-ups. It also means that I don't
waste I/O cycles on updating atimes on often-used binaries and libraries
(which of course could also be done with noatime).

I've seen some boot-from-flash setups with /usr on a hard drive.

Basically, if Fedora is going to follow the FHS at all, bugs like 626007
should be fixed, not ignored because somebody doesn't like a separate
/usr.

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Old 10-19-2010, 02:35 PM
Matthew Garrett
 
Default rawhide report: 20101019 changes

On Tue, Oct 19, 2010 at 09:24:10AM -0500, Chris Adams wrote:

> A smaller / that is written to less often is less susceptible to errors.
> If you don't allocate enough space for / up front, you can move /usr and
> /opt to separate filesystems later. /opt can be completely
> unpredictable in space usage, due to vendor RPMs dumping stuff in /opt
> (see Dell's OMSA, that puts everything, including logs, under /opt).

So, LVM?

> I personally don't use a separate /usr on desktops, only on servers. On
> my servers, /usr is mounted read-only, as an extra protection against
> accidental (or even intentional) screw-ups. It also means that I don't
> waste I/O cycles on updating atimes on often-used binaries and libraries
> (which of course could also be done with noatime).

mount --bind /usr /usr
mount -o ro,remount /usr

> I've seen some boot-from-flash setups with /usr on a hard drive.

The rational thing there is for the flash to be /boot, not /.

> Basically, if Fedora is going to follow the FHS at all, bugs like 626007
> should be fixed, not ignored because somebody doesn't like a separate
> /usr.

I don't think we gain anything from following the FHS on this point
other than the ability to have /usr as a separate partition, and think
that's a pretty circular argument.

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Old 10-19-2010, 02:37 PM
Lennart Poettering
 
Default rawhide report: 20101019 changes

On Tue, 19.10.10 14:43, Paul Howarth (paul@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@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

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Old 10-19-2010, 02:38 PM
seth vidal
 
Default rawhide report: 20101019 changes

On Tue, 2010-10-19 at 14:56 +0100, Matthew Garrett wrote:
> On Tue, Oct 19, 2010 at 02:43:33PM +0100, Paul Howarth wrote:
>
> > 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?
>
> What's the benefit in having /usr or /opt as separate filesystems?
>

/opt is a location filled with vendor detritus on a lot of systems -
sometimes managed by rpms, sometimes not. It's not uncommon to have /opt
automounted via nfs. Additionally, on some workstastion systems /opt is
a separate drive managed by the 'local admin' of the machine and filled
with whatever 3rd party software they need for their instance.

/usr is frequently given different mount options (like noatime, for
example) or mounted readonly to prevent unnecessary writes to the
system.

Additionally, since our software in fedora has a trickle down impact on
users in rhel-land I think you'll find that this will have to be done,
eventually for them.

Finally, I'm more than a little concerned by the tone of comments in
that bug report. It's troubling.

-sv


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Old 10-19-2010, 02:51 PM
Stanislav Ochotnicky
 
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On 10/19/2010 04:37 PM, Lennart Poettering wrote:
> 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).

Where did you get that idea? From Gentoo installation handbook:

"The number of partitions is highly dependent on your environment. For
instance, if you have lots of users, you will most likely want to have
your /home separate as it increases security and makes backups easier.
If you are installing Gentoo to perform as a mailserver, your /var
should be separate as all mails are stored inside /var. A good choice of
filesystem will then maximise your performance. Gameservers will have a
separate /opt as most gaming servers are installed there. The reason is
similar for /home: security and backups. *You will definitely want to
keep /usr big*: not only will it contain the majority of applications,
the Portage tree alone takes around 500 Mbyte excluding the various
sources that are stored in it."

Before replying and saying that "is just says /usr has to be big".
Please read whole
http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=4
(part "How Many and How Big?")

I won't even comment on whole idea of not supporting separate /usr in
Fedora...makes me sad.

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