[Pkg-sysvinit-devel] Bug#572733: support for mounting other kernel filesystems

[Marco d'Itri]

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
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