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

[Ian Stakenvicius]

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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.  #2, if 'nofail' is specified on the nfs
filesystem mounts (or there aren't any nfs filesystem mounts) in
/etc/fstab then the nfsclient 'need' would be a 'use' at most, which
means that there won't be any failures for other net-based filesystems
and netmount would succeed (assuming those other network filesystem
types don't trigger a failure).

I don't know if #2 is enough to keep the userbase happy that expects
netmount to succeed in mounting other network filesystems.  I think we
need to ask.

What we would essentially end up with is a situation where 'nofail' on
the nfs mount points in fstab provides exactly the same behaviour that
netmount has now (assuming other network filesystems succeed), while
without 'nofail' netmount will fail if there's an nfs filesystem to
mount and nfsclient doesn't start, but will bring in nfsclient even if
its not in the runlevel and will succeed when nfsclient does start.



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