Debian Bug report logs - #572733
support for mounting other kernel filesystems

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Package: initscripts; Maintainer for initscripts is Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>; Source for initscripts is src:sysvinit.

Reported by: Marco d'Itri <md@linux.it>

Date: Sat, 6 Mar 2010 04:06:01 UTC

Severity: normal

Found in version sysvinit/2.87dsf-8.1

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Report forwarded to debian-bugs-dist@lists.debian.org, md@linux.it, debian-devel@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sat, 06 Mar 2010 04:06:05 GMT) Full text and rfc822 format available.

Acknowledgement sent to Marco d'Itri <md@linux.it>:
New Bug report received and forwarded. Copy sent to md@linux.it, debian-devel@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sat, 06 Mar 2010 04:06:05 GMT) Full text and rfc822 format available.

Message #5 received at submit@bugs.debian.org (full text, mbox):

From: Marco d'Itri <md@linux.it>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Subject: support for mounting other kernel filesystems
Date: Sat, 6 Mar 2010 05:03:05 +0100
[Message part 1 (text/plain, inline)]
Package: initscripts
Version: 2.87dsf-8.1
Severity: normal

I am tentatively opening this bug on initscripts to start a discussion,
but I am unsure about the best way to solve the problem.
Still, I believe it is important to solve it in time for the next
release because it is a prerequisite of some important features mostly
related to virtualization.

Currently the initscripts package mounts some well known kernel file
systems like proc, sys and devpts, but there are a few others which
AFAIK no package currently deals with:
- cgroups (needed for accounting and management of system resources)
- hugetlbfs (provides large memory pages, an optimization useful for
  some applications)

While some other filesystems are mounted by specific packages (e.g.
rpc_pipefs by nfs-common and fusectl by fuse), these have no common
package which can do it.

The system administrator cannot even just add them to fstab, because
there is nothing to create the mount points in /dev after each boot.


Possible solutions:
- for each filesystem create a new package shipping an init script
  which mounts it
- have the initscripts package mount the filesystems 
- have the initscripts package create the mount points for filesystems
  listed in fstab and mounted below /dev
- have the udev package create the mount points for filesystems
  listed in fstab and mounted below /dev
- others?

#3 and #4 are not incompatible with #1 and #2.


If there will be no action from other maintainers then I will implement
#4, but I am not really advocating it over the others.


Open questions:

Do we agree to mount these filesystems on /dev/ subdirectories?
Fedora[1] uses /dev/hugepages/ for hugetlbfs, and while we had a
discussion on debian-devel@ about where cgroups should be mounted there
was no clear winner.
The upstream developers do not take a position either, but /dev/cgroup/
and /dev/cgroups/ are popular choices.

What should the default be? Mounting or not mounting the filesystems
if they are available? Does mounting one of these filesystems has
negative implications if it is not needed?
I suppose that at least some RAM will be used, but is it enough to care?

If they should not be mounted by default, is fstab the best way for the
system administrator to configure this or should an init script be used
anyway?


[1] http://fedoraproject.org/wiki/Features/KVM_Huge_Page_Backed_Memory

-- 
ciao,
Marco
[signature.asc (application/pgp-signature, inline)]

Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sat, 06 Mar 2010 06:33:02 GMT) Full text and rfc822 format available.

Acknowledgement sent to Mike Hommey <mh@glandium.org>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sat, 06 Mar 2010 06:33:03 GMT) Full text and rfc822 format available.

Message #10 received at 572733@bugs.debian.org (full text, mbox):

From: Mike Hommey <mh@glandium.org>
To: Marco d'Itri <md@linux.it>, 572733@bugs.debian.org
Cc: debian-devel@lists.debian.org
Subject: Re: Bug#572733: support for mounting other kernel filesystems
Date: Sat, 6 Mar 2010 07:30:47 +0100
On Sat, Mar 06, 2010 at 05:03:05AM +0100, Marco d'Itri wrote:
> Do we agree to mount these filesystems on /dev/ subdirectories?
> Fedora[1] uses /dev/hugepages/ for hugetlbfs, and while we had a
> discussion on debian-devel@ about where cgroups should be mounted there
> was no clear winner.
> The upstream developers do not take a position either, but /dev/cgroup/
> and /dev/cgroups/ are popular choices.

/dev/something just feels so wrong. /dev contains block and character
devices, and almost nothing else (except some udev and initramfs files)
Why should cgroups control files, which are hardly device files, be
found under /dev ?

Mike




Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sat, 06 Mar 2010 09:57:03 GMT) Full text and rfc822 format available.

Acknowledgement sent to Petter Reinholdtsen <pere@hungry.com>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sat, 06 Mar 2010 09:57:03 GMT) Full text and rfc822 format available.

Message #15 received at 572733@bugs.debian.org (full text, mbox):

From: Petter Reinholdtsen <pere@hungry.com>
To: Marco d'Itri <md@linux.it>, 572733@bugs.debian.org
Subject: Re: [Pkg-sysvinit-devel] Bug#572733: support for mounting other kernel filesystems
Date: Sat, 6 Mar 2010 10:56:34 +0100
[Marco d'Itri]
> Currently the initscripts package mounts some well known kernel file
> systems like proc, sys and devpts, but there are a few others which
> AFAIK no package currently deals with:
> - cgroups (needed for accounting and management of system resources)

I thought the libcgroup package handled this one, but might be wrong.

> - hugetlbfs (provides large memory pages, an optimization useful for
>   some applications)

Did not know about this one.

> Possible solutions:
> - for each filesystem create a new package shipping an init script
>   which mounts it
> - have the initscripts package mount the filesystems 
> - have the initscripts package create the mount points for filesystems
>   listed in fstab and mounted below /dev
> - have the udev package create the mount points for filesystems
>   listed in fstab and mounted below /dev
> - others?
> 
> #3 and #4 are not incompatible with #1 and #2.

In my opinion initscripts should limit itself to mount special file
system that should be available on all or almost all installations and
that do not introduce a security problem when mounted, and leave it to
other packages to handle mounting of less common file system types.
The request for mounting debugfs by default has so far been denied, as
it have a rather special use case and can be seen as a security
problem.

I do not know cgroups and hugetlbfs well enought to know how they do
in this regard.

> If there will be no action from other maintainers then I will
> implement #4, but I am not really advocating it over the others.

For file system that should be mounted on Linux, depending on udev
mith be ok, but for file systems that also should be mounted on
kFreeBSD, I am told udev do not work and using udev is not an option.
I suspect cgroups and hugetlbfs are linux specific, but wanted to
mention the issue to be sure it is known.

On Linux, using udev is supposed to be optional, but it is getter
harder and harder to to avoid it, so I am not sure we want to spend
extra effort to make it easier to drop udev from an installation.

> Do we agree to mount these filesystems on /dev/ subdirectories?

I have no opinion on the mount point location, but would like all
distributions to agree on the same location to make it easier for
users and application writers to move applications from OS to OS.

> The upstream developers do not take a position either, but
> /dev/cgroup/ and /dev/cgroups/ are popular choices.

What are the other choices?  What do Ubuntu, SuSe, Mandriva, Gentoo
and the other distributions do?  Which mount point is most commonly
used?

> What should the default be? Mounting or not mounting the filesystems
> if they are available? Does mounting one of these filesystems has
> negative implications if it is not needed?

Adding code to initscripts for file systems that are rarely used slow
down the boot.  I suspect the slowdown is neglectabe, thought, but it
is an idea to measure it, to know how much impact it has on systems
not using these new file systems.

> I suppose that at least some RAM will be used, but is it enough to care?

I do not believe a few bytes spent by the kernel is enought to care.
I assume the kernel only allocate a few structs to keep status info on
the file systems.  If huge amount of memory is allocated, we need to
reconsider.

> If they should not be mounted by default, is fstab the best way for
> the system administrator to configure this or should an init script
> be used anyway?

Do not know.  For me it depend on how many installations should have
these file systems mounted.  If it is all or almost all -> init.d
scripts in the initscripts package and if it is some instalations ->
sysadmin can add it himself or separate pacage.

Happy hacking,
-- 
Petter Reinholdtsen




Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sun, 07 Mar 2010 02:36:05 GMT) Full text and rfc822 format available.

Acknowledgement sent to md@Linux.IT (Marco d'Itri):
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sun, 07 Mar 2010 02:36:05 GMT) Full text and rfc822 format available.

Message #20 received at 572733@bugs.debian.org (full text, mbox):

From: md@Linux.IT (Marco d'Itri)
To: 572733@bugs.debian.org, debian-devel@lists.debian.org
Subject: Re: Bug#572733: support for mounting other kernel filesystems
Date: Sun, 7 Mar 2010 02:51:11 +0100
[Message part 1 (text/plain, inline)]
On Mar 06, Petter Reinholdtsen <pere@hungry.com> wrote:

> > - cgroups (needed for accounting and management of system resources)
> I thought the libcgroup package handled this one, but might be wrong.
I understand that the cgconfig program from cgroup-bin does mount it
(in /mnt/cgroups/cpu, which I believe to be totally broken since /mnt
is not supposed to have subdirectories), but I do not think everybody
needs or wants to use cgconfig.

> In my opinion initscripts should limit itself to mount special file
> system that should be available on all or almost all installations and
> that do not introduce a security problem when mounted, and leave it to
> other packages to handle mounting of less common file system types.
Write access to cgroups and hugetlbfs is restricted to root by default.

> The request for mounting debugfs by default has so far been denied, as
> it have a rather special use case and can be seen as a security
> problem.
debugfs also already has a /sys/kernel/debug/ so it can easily be dealt
with in fstab. Since AFAIK it is not used by regular programs I see no
harm in having to configure it manually.

> For file system that should be mounted on Linux, depending on udev
> mith be ok, but for file systems that also should be mounted on
> kFreeBSD, I am told udev do not work and using udev is not an option.
> I suspect cgroups and hugetlbfs are linux specific, but wanted to
> mention the issue to be sure it is known.
Obviously these are Linux-specific filesystems. The porters to other
kernels will deal with their own system-specific filesystems...

> On Linux, using udev is supposed to be optional, but it is getter
> harder and harder to to avoid it, so I am not sure we want to spend
> extra effort to make it easier to drop udev from an installation.
udev is not intended to be optional, even if some systems currently work
well enough without udev nobody should rely on this to be true in the
future as well.

> I have no opinion on the mount point location, but would like all
> distributions to agree on the same location to make it easier for
> users and application writers to move applications from OS to OS.
Good luck. Obviously this will not happen in time for squeeze, so we
need a solution anyway.
The cgroups upstream maintainers stated that they are not interested in
mandating any specific location.

> > The upstream developers do not take a position either, but
> > /dev/cgroup/ and /dev/cgroups/ are popular choices.
> What are the other choices?  What do Ubuntu, SuSe, Mandriva, Gentoo
> and the other distributions do?  Which mount point is most commonly
> used?
I do not think other distributions have infrastructure to mount this
filesystem except for what is provided by cgconfig.
The upstream developers stated that they do not want to recommend any
specific directory, I think the only common alternative I have seen is
/cgroups/.

> Do not know.  For me it depend on how many installations should have
> these file systems mounted.  If it is all or almost all -> init.d
> scripts in the initscripts package and if it is some instalations ->
> sysadmin can add it himself or separate pacage.
The sysadmin currently CANNOT mount these filesystems by itself below
/dev because there is no mount point at boot time.
This may be the best solution, but it still needs some work in a
standard package.


On Mar 06, Mike Hommey <mh@glandium.org> wrote:

> /dev/something just feels so wrong. /dev contains block and character
> devices, and almost nothing else (except some udev and initramfs files)
> Why should cgroups control files, which are hardly device files, be
> found under /dev ?
Why not? /dev/pts/ is a kernel filesystem mounted below /dev, and /dev
itself is a kernel filesystem (tmpfs or devtmpfs).
And /dev will still be much less controversial than mount points in / .

-- 
ciao,
Marco
[signature.asc (application/pgp-signature, inline)]

Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sun, 07 Mar 2010 08:12:05 GMT) Full text and rfc822 format available.

Acknowledgement sent to Mike Hommey <mh@glandium.org>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sun, 07 Mar 2010 08:12:05 GMT) Full text and rfc822 format available.

Message #25 received at 572733@bugs.debian.org (full text, mbox):

From: Mike Hommey <mh@glandium.org>
To: 572733@bugs.debian.org, debian-devel@lists.debian.org
Subject: Re: Bug#572733: support for mounting other kernel filesystems
Date: Sun, 7 Mar 2010 09:10:43 +0100
On Sun, Mar 07, 2010 at 02:51:11AM +0100, Marco d'Itri wrote:
> > /dev/something just feels so wrong. /dev contains block and character
> > devices, and almost nothing else (except some udev and initramfs files)
> > Why should cgroups control files, which are hardly device files, be
> > found under /dev ?
> Why not? /dev/pts/ is a kernel filesystem mounted below /dev, and /dev
> itself is a kernel filesystem (tmpfs or devtmpfs).

And both only contain character or block devices (or occasional
directories). Nothing else.

Mike




Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sun, 07 Mar 2010 14:45:06 GMT) Full text and rfc822 format available.

Acknowledgement sent to md@Linux.IT (Marco d'Itri):
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sun, 07 Mar 2010 14:45:06 GMT) Full text and rfc822 format available.

Message #30 received at 572733@bugs.debian.org (full text, mbox):

From: md@Linux.IT (Marco d'Itri)
To: 572733@bugs.debian.org, debian-devel@lists.debian.org
Subject: Re: Bug#572733: support for mounting other kernel filesystems
Date: Sun, 7 Mar 2010 15:42:51 +0100
[Message part 1 (text/plain, inline)]
On Mar 07, Mike Hommey <mh@glandium.org> wrote:

> > Why not? /dev/pts/ is a kernel filesystem mounted below /dev, and /dev
> > itself is a kernel filesystem (tmpfs or devtmpfs).
> And both only contain character or block devices (or occasional
> directories). Nothing else.
I meant /dev/shm.

-- 
ciao,
Marco
[signature.asc (application/pgp-signature, inline)]

Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Thu, 11 Mar 2010 21:27:05 GMT) Full text and rfc822 format available.

Acknowledgement sent to Henrique de Moraes Holschuh <hmh@debian.org>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Thu, 11 Mar 2010 21:27:05 GMT) Full text and rfc822 format available.

Message #35 received at 572733@bugs.debian.org (full text, mbox):

From: Henrique de Moraes Holschuh <hmh@debian.org>
To: Marco d'Itri <md@linux.it>, 572733@bugs.debian.org, debian-devel@lists.debian.org
Subject: Re: [Pkg-sysvinit-devel] Bug#572733: support for mounting other kernel filesystems
Date: Thu, 11 Mar 2010 18:24:26 -0300
On Sat, 06 Mar 2010, Mike Hommey wrote:
> /dev/something just feels so wrong. /dev contains block and character
> devices, and almost nothing else (except some udev and initramfs files)

Not really.  There's the whole /dev/shm crap (which one is not supposed to
access directly anyway).

> Why should cgroups control files, which are hardly device files, be
> found under /dev ?

I'd rather have it in /sys, yes, but doing so would be dangerous (*never*
mount anything in there that the kernel developers don't expect, they may
decide to use your mountpoint to export something later on...).

IMO, it is much better to have it /dev somewhere, than in / or /mnt, or
worse, somewhere in /etc.

Maybe we should push for a /kernel in / and mount this kind of crap there,
since /sys is *not* fair game.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh




Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Wed, 17 Mar 2010 08:03:10 GMT) Full text and rfc822 format available.

Acknowledgement sent to Frank Lin PIAT <fpiat@klabs.be>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Wed, 17 Mar 2010 08:03:10 GMT) Full text and rfc822 format available.

Message #40 received at 572733@bugs.debian.org (full text, mbox):

From: Frank Lin PIAT <fpiat@klabs.be>
To: 572733@bugs.debian.org
Subject: Fixed GID for hugetables / hugetlb_shm_group
Date: Wed, 17 Mar 2010 09:00:43 +0100
Hello,

Please use a fixed/reserved group for hugetables, since
vm.hugetlb_shm_group only allows GID:

% echo my-hugetlbfs >  /proc/sys/vm/hugetlb_shm_group && echo done
-bash: echo: write error: Invalid argument
% echo 2021 >  /proc/sys/vm/hugetlb_shm_group && echo done
done

Would it be possible to configure that group in /etc/sysctl.conf by
default.

BTW, people interested or involved with Hugepages in Debian are welcome
to read/review/contribute to:  http://wiki.debian.org/Hugepages

Thanks

Franklin





Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sun, 06 Jun 2010 09:21:03 GMT) Full text and rfc822 format available.

Acknowledgement sent to md@Linux.IT (Marco d'Itri):
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sun, 06 Jun 2010 09:21:03 GMT) Full text and rfc822 format available.

Message #45 received at 572733@bugs.debian.org (full text, mbox):

From: md@Linux.IT (Marco d'Itri)
To: 572733@bugs.debian.org
Subject: Re: Bug#572733: support for mounting other kernel filesystems
Date: Sun, 6 Jun 2010 11:09:26 +0200
[Message part 1 (text/plain, inline)]
On Mar 06, Marco d'Itri <md@linux.it> wrote:

> Currently the initscripts package mounts some well known kernel file
> systems like proc, sys and devpts, but there are a few others which
> AFAIK no package currently deals with:
Are there any news about this?

-- 
ciao,
Marco
[signature.asc (application/pgp-signature, inline)]

Information forwarded to debian-bugs-dist@lists.debian.org, Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>:
Bug#572733; Package initscripts. (Sun, 06 Jun 2010 09:36:03 GMT) Full text and rfc822 format available.

Acknowledgement sent to Petter Reinholdtsen <pere@hungry.com>:
Extra info received and forwarded to list. Copy sent to Debian sysvinit maintainers <pkg-sysvinit-devel@lists.alioth.debian.org>. (Sun, 06 Jun 2010 09:36:03 GMT) Full text and rfc822 format available.

Message #50 received at 572733@bugs.debian.org (full text, mbox):

From: Petter Reinholdtsen <pere@hungry.com>
To: Marco d'Itri <md@Linux.IT>, 572733@bugs.debian.org
Subject: Re: [Pkg-sysvinit-devel] Bug#572733: support for mounting other kernel filesystems
Date: Sun, 6 Jun 2010 11:33:37 +0200
[Marco d'Itri]
> Are there any news about this?

Nope.  No-one spend time to investigate how other distros handle this,
nor to check if existing packages already handle the file systems in
question.  It would be great if you or someone else took the time to
investiage this.

There is also
<URL: http://lists.alioth.debian.org/pipermail/pkg-sysvinit-devel/2010-June/004324.html >,
partly explaing why. :)

Happy hacking,
-- 
Petter Reinholdtsen




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