Re: [gentoo-dev] Re: rfc: improve file system mounting and unmounting in OpenRC

[William Hubbs]

On Fri, Aug 07, 2015 at 01:39:25PM -0400, Ian Stakenvicius wrote:
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> On 07/08/15 12:59 PM, William Hubbs wrote:
> > On Fri, Aug 07, 2015 at 12:10:56PM -0400, Ian Stakenvicius wrote:
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> >> On 07/08/15 11:30 AM, William Hubbs wrote:
> >>> On Thu, Aug 06, 2015 at 08:07:44PM -0400, Ian Stakenvicius
> >>> wrote:
> >>>>
> >>>> Can we get "nofail" immediately in the mount -a variants of
> >>>> localmount/netmount and expand that in netmount to make the
> >>>> nfsclient dep be a "use" or a "need" depending on if it's set
> >>>> or not??  That would imo kill the existing bug that started
> >>>> all of this too.
> >>>
> >>> Sure, I can get the nofail support in pretty quick, and I
> >>> think that is a feature we should have.
> >>>
> >>> Right now, netmount is using the use dependency to make sure
> >>> network file system utilities are started before us. Because
> >>> of the all-or-nothing nature of netmount, we can't switch
> >>> those dependencies to need. It would cause netmount to fail if
> >>> one of those utilities fails to start.  The use dependency is
> >>> the best one we can use at this time, and a migration path was
> >>> specifically laid out in the news item.
> >>>
> >>
> >> My thinking here is that, unless network mounts in fstab are
> >> listed as 'nofail', that netmount failing due to the dependent
> >> services not being able to start would be a valid case.
> >> Sysadmins that don't want netmount to fail no matter what would
> >> be able to use 'nofail' to ensure that happens.
> >>
> >> This is of course predicated on (1) it being a good idea, and
> >> (2) fstabinfo or whatever the check currently is that would add
> >> nfsclient to depend() could easily swap 'use' for 'need' based on
> >> the (lack of) existence of the nofail attribute in fstab.
> >
> > The issue with using the need dependency is that netmount is not
> > granular enough. It mounts all types of network file systems, so if
> > we fail because nfs is a need dependency and doesn't start, no
> > other types of network file systems that use daemons will be
> > mounted. That's what I meant by all-or-nothing.
> >
> > William
> >
>
> Yes I follow that.  My thoughts are #1, netmount (and localmount for
> that matter) are all-or-nothing things; so if the service fails then I
> don't think anything can necessarily be assumed as to which mounts
> succeeded and which don't.

Yes, they are, but mount and umount -a are not. They can report partial
failures (check the exit codes).

If I switch to using need dependencies for the file system clients, and
one fails to start, mount -a would never run, which means NO net-based
file systems that use clients would be mounted.

My thinking is to allow things to mount that can, but still report it as
a failure if everything doesn't mount.

Thoughts?

William