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Old 10-16-2011, 06:44 PM
Zac Medico
 
Default supporting /usr on separate partition

On 10/16/2011 05:52 AM, Ian Stakenvicius wrote:
> On 15/10/11 06:07 PM, Zac Medico wrote:
>> On 10/15/2011 01:57 AM, Wulf C. Krueger wrote:
>>> On 15.10.2011 10:42, Michael Schreckenbauer wrote:
>>>> in what way will exherbo deal wih this mess? Are there any plans?
>>>
>>> We don't support /usr on a separate partition. People can, of course, do
>>> that and I'll point them to dracut for creating an initramfs.
>>>
>>> Or they can do whatever works for them. People using Exherbo are
>>> expected to be able to deal with such stuff.
>>
>> I don't think it's a good idea for Gentoo to encourage users to have
>> /usr on a separate partition. We should probably remove the separate
>> /usr partition from "Code Listing 2.1: Filesystem usage example" in our
>> handbook:
>>
>> http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&chap=4#doc_chap2_pre1
>>
>
> For desktops i've never seen much purpose of having /usr on its own
> partition (or more than the usual 3 of /boot,/,swap tbh), but for
> servers I have seen a lot of configurations over the years that put /usr
> on its own partition. Exherbo aside, I would expect that Gentoo would
> (continue to?) support doing this.

Well, you'll have to define the meaning of "support" in this context. I
simply said that it shouldn't be encouraged, with me reason being that
it tends to add unnecessary complexity (in violation of the KISS
principle [1]).

> As per the documentation itself, Code Listing 2.1 is i believe an
> example of what is possible, not what we are encouraging users to do.
> That doc seems pretty clear that the default is partitioning scheme is
> the default /boot,/,swap ...

Why should our main installation docs mention a configuration that the
vast majority of our users (all?) would be better off without?

> And just to confirm, doesn't udev's installation (which is primarily in
> /lib) support /usr on a separate partition now, without an initramfs?

What's the benefit of having /usr on a separate partition anyway? The
only somewhat reasonable explanation that I've heard is so that it can
be mounted readonly. If people want that, I think it's perfectly
reasonable to expect them to use either an initramfs or a simple linuxrc
approach [2] to ensure that /usr is mounted before init starts. For
complex configurations like this, we can have a separate page of docs,
like the raid+lvm2 page [3], and link it from the main installation docs
if we want.

[1] http://en.wikipedia.org/wiki/KISS_principle
[2]
http://archives.gentoo.org/gentoo-dev/msg_20749880f5bc5feda141488498729fe8.xml
[3] http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml
--
Thanks,
Zac
 
Old 10-16-2011, 07:36 PM
Graham Murray
 
Default supporting /usr on separate partition

Zac Medico <zmedico@gentoo.org> writes:

> What's the benefit of having /usr on a separate partition anyway? The
> only somewhat reasonable explanation that I've heard is so that it can
> be mounted readonly.

One benefit, especially in a large server 'farm' is that several servers
can share the same /usr by NFS mounting, read-only, the same partition
on all of the servers. This both ensures that all the servers are kept
in-step and greatly simplifies the upgrade process.
 
Old 10-16-2011, 07:40 PM
Michał Górny
 
Default supporting /usr on separate partition

On Sun, 16 Oct 2011 20:36:23 +0100
Graham Murray <graham@gmurray.org.uk> wrote:

> Zac Medico <zmedico@gentoo.org> writes:
>
> > What's the benefit of having /usr on a separate partition anyway?
> > The only somewhat reasonable explanation that I've heard is so that
> > it can be mounted readonly.
>
> One benefit, especially in a large server 'farm' is that several
> servers can share the same /usr by NFS mounting, read-only, the same
> partition on all of the servers. This both ensures that all the
> servers are kept in-step and greatly simplifies the upgrade process.

Unless upgrade involves files being outside of /usr.

--
Best regards,
Michał Górny
 
Old 10-17-2011, 04:02 PM
Ian Stakenvicius
 
Default supporting /usr on separate partition

Splitting this up since i'm kind of starting two threads here..

----- Documentation discussion -----
On 16/10/11 02:44 PM, Zac Medico wrote:
>
> Well, you'll have to define the meaning of "support" in this context. I
> simply said that it shouldn't be encouraged, with me reason being that
> it tends to add unnecessary complexity (in violation of the KISS
> principle [1]).
>

I would agree with this (that it shouldn't be encouraged), but I don't
think the Handbook is encouraging it now, as it is written..


>> As per the documentation itself, Code Listing 2.1 is i believe an
>> example of what is possible, not what we are encouraging users to do.
>> That doc seems pretty clear that the default is partitioning scheme is
>> the default /boot,/,swap ...
>
> Why should our main installation docs mention a configuration that the
> vast majority of our users (all?) would be better off without?
>

You'd have to talk to the original authors to confirm but I believe this
would be to illustrate the possibilities and give users info that will
let them think about their partitioning scheme, instead of telling them
what to do. Essentially, to introduce and educate about partitions and
filesystems.

(it is the Gentoo Handbook, not the Gentoo Quick Install Howto, after all)


> What's the benefit of having /usr on a separate partition anyway?

I think that's covered rather generically in the guide -- different fs
type, won't run out of space on / if /usr fills up, different mount
options (ie, mounting ROOT ro and /usr rw); and of course if /usr is on
separate physical media (ie, a nice big RAID, while / is on, say, a
small SSD).


----- Support/implementation discussion -----

> ... If people want that, I think it's perfectly
> reasonable to expect them to use either an initramfs or a simple linuxrc
> approach [2] to ensure that /usr is mounted before init starts.

...this would make sense, although in terms of "support" i think it
would be appropriate that we would provide this linuxrc wrapper on any
init system that needs /usr mounted.
 
Old 10-17-2011, 05:24 PM
Zac Medico
 
Default supporting /usr on separate partition

On 10/17/2011 09:02 AM, Ian Stakenvicius wrote:
> Splitting this up since i'm kind of starting two threads here..
>
> ----- Documentation discussion -----
> On 16/10/11 02:44 PM, Zac Medico wrote:
>>
>> Well, you'll have to define the meaning of "support" in this context. I
>> simply said that it shouldn't be encouraged, with me reason being that
>> it tends to add unnecessary complexity (in violation of the KISS
>> principle [1]).
>>
>
> I would agree with this (that it shouldn't be encouraged), but I don't
> think the Handbook is encouraging it now, as it is written..

It depends on how you define "encouraging" in this context. The fact
that /usr is shown as a separate partition might be considered
"suggestive" if not "encouraging". If a user takes that suggestion
without knowing the consequences (special initramfs or linuxrc init
wrapper configuration), then then it could cause some disappointment
when they finally discover the consequences.

> ----- Support/implementation discussion -----
>
>> ... If people want that, I think it's perfectly
>> reasonable to expect them to use either an initramfs or a simple linuxrc
>> approach [2] to ensure that /usr is mounted before init starts.
>
> ...this would make sense, although in terms of "support" i think it
> would be appropriate that we would provide this linuxrc wrapper on any
> init system that needs /usr mounted.

If someone wants to take on the burden of maintaining an init wrapper
like that, then I guess that's fine. However, I wouldn't consider it to
be an absolute requirement. I think it would be fine (maybe preferable)
to simply provide a doc that describes how to mount /usr via an
initramfs or linuxrc init wrapper. Such a doc would only be needed by
those users who require that /usr be on a separate partition.
--
Thanks,
Zac
 
Old 10-17-2011, 05:50 PM
Ian Stakenvicius
 
Default supporting /usr on separate partition

...and recombining again..
On 2011-10-17, at 1:24 PM, Zac Medico <zmedico@gentoo.org> wrote:

On 10/17/2011 09:02 AM, Ian Stakenvicius wrote:
Splitting this up since i'm kind of starting two threads here..

----- Documentation discussion -----
On 16/10/11 02:44 PM, Zac Medico wrote:

Well, you'll have to define the meaning of "support" in this context. I
simply said that it shouldn't be encouraged, with me reason being that
it tends to add unnecessary complexity (in violation of the KISS
principle [1]).


I would agree with this (that it shouldn't be encouraged), but I don't
think the Handbook is encouraging it now, as it is written..

It depends on how you define "encouraging" in this context. The fact
that /usr is shown as a separate partition might be considered
"suggestive" if not "encouraging". If a user takes that suggestion
without knowing the consequences (special initramfs or linuxrc init
wrapper configuration), then then it could cause some disappointment
when they finally discover the consequences.

----- Support/implementation discussion -----

... If people want that, I think it's perfectly
reasonable to expect them to use either an initramfs or a simple linuxrc
approach [2] to ensure that /usr is mounted before init starts.

...this would make sense, although in terms of "support" i think it
would be appropriate that we would provide this linuxrc wrapper on any
init system that needs /usr mounted.

If someone wants to take on the burden of maintaining an init wrapper
like that, then I guess that's fine. However, I wouldn't consider it to
be an absolute requirement. I think it would be fine (maybe preferable)
to simply provide a doc that describes how to mount /usr via an
initramfs or linuxrc init wrapper. Such a doc would only be needed by
those users who require that /usr be on a separate partition.

This makes sense. *So the Handbook could be updated with a caveat after the large partition example to say something like "/usr on it's own partition needs special consideration, please see XXXXX" ... this works.
 
Old 10-17-2011, 05:55 PM
Samuli Suominen
 
Default supporting /usr on separate partition

On 10/17/2011 08:50 PM, Ian Stakenvicius wrote:

please disable HTML in your mail client.
 
Old 10-17-2011, 07:18 PM
Ian Stakenvicius
 
Default supporting /usr on separate partition

On 17/10/11 01:55 PM, Samuli Suominen wrote:
> On 10/17/2011 08:50 PM, Ian Stakenvicius wrote:
>
> please disable HTML in your mail client.
>


CRAP. sorry all. will stop emailing from my phone.
 
Old 10-17-2011, 08:01 PM
Sven Vermeulen
 
Default supporting /usr on separate partition

On Mon, Oct 17, 2011 at 01:50:04PM -0400, Ian Stakenvicius wrote:
> > If someone wants to take on the burden of maintaining an init wrapper
> > like that, then I guess that's fine. However, I wouldn't consider it to
> > be an absolute requirement. I think it would be fine (maybe preferable)
> > to simply provide a doc that describes how to mount /usr via an
> > initramfs or linuxrc init wrapper. Such a doc would only be needed by
> > those users who require that /usr be on a separate partition.
>
> This makes sense. So the Handbook could be updated with a caveat after
> the large partition example to say something like "/usr on it's own
> partition needs special consideration, please see XXXXX" ... this$
> works.

(Ian, it's a general reply, not specific to your e-mail)

I've updated the Gentoo Handbook just a few moments ago to mention something
like this in the introduction of the partition section "How Many and How
Big":

--Snippet from the commit result:
<p>
However, multiple partitions have disadvantages as well. If not configured
properly, you will have a system with lots of free space on one partition
and none on another. Another nuisance is that separate partitions - especially
for important mountpoints like <path>/usr</path> or <path>/var</path> -
often require the administrator to boot with an initramfs to mount the partition
before other boot scripts start. This isn't always the case though, so YMMV.
</p>

<p>
There is also a 15-partition limit for SCSI and SATA unless you use GPT
labels.
</p>
--End Snippet

Now, I must say I find it strange that people think that the Gentoo Handbook
suggests users to use a separate /usr partition. It does not. The default
partitioning that we use is a separate /boot (yes, this can and has been
debated in the past, I'm not going to change this) and / with a separate
swap partition. Nothing more, nothing less. There are a few code listings
where an example output is given which holds a separate /usr but I hope all
those listings are clear that they are examples.

It also states that this is an example we use in the Gentoo Handbook and
that it depends on the user how he wants his partition scheme layed out.

I'm hoping that the above update clarifies this sufficiently so that huge
threads like this one don't need to reappear again ;-) If you think it is
still unclear or needs improvements left or right, don't hesitate to mail me
or, even better, file a bugreport (I act better on bug reports than on
e-mails).

Oh, and I use a separate /usr with no initramfs (yet), with software raid
and lvm2.

/me quickly hides

Wkr,
Sven Vermeulen
 
Old 10-17-2011, 08:31 PM
Zac Medico
 
Default supporting /usr on separate partition

On 10/17/2011 01:01 PM, Sven Vermeulen wrote:
> --Snippet from the commit result:
> <p>
> However, multiple partitions have disadvantages as well. If not configured
> properly, you will have a system with lots of free space on one partition
> and none on another. Another nuisance is that separate partitions - especially
> for important mountpoints like <path>/usr</path> or <path>/var</path> -
> often require the administrator to boot with an initramfs to mount the partition
> before other boot scripts start. This isn't always the case though, so YMMV.
> </p>
>
> <p>
> There is also a 15-partition limit for SCSI and SATA unless you use GPT
> labels.
> </p>
> --End Snippet
>
> Now, I must say I find it strange that people think that the Gentoo Handbook
> suggests users to use a separate /usr partition. It does not. The default
> partitioning that we use is a separate /boot (yes, this can and has been
> debated in the past, I'm not going to change this) and / with a separate
> swap partition. Nothing more, nothing less. There are a few code listings
> where an example output is given which holds a separate /usr but I hope all
> those listings are clear that they are examples.

Even if you don't consider them to be formal "suggestions", their mere
presence as examples lends them credence.

> It also states that this is an example we use in the Gentoo Handbook and
> that it depends on the user how he wants his partition scheme layed out.
>
> I'm hoping that the above update clarifies this sufficiently so that huge
> threads like this one don't need to reappear again ;-) If you think it is
> still unclear or needs improvements left or right, don't hesitate to mail me
> or, even better, file a bugreport (I act better on bug reports than on
> e-mails).

I think the new "disadvantages" section that you posted should convey an
appropriate level of caution. Thanks!
--
Thanks,
Zac
 

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