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

[Daniel Campbell (zlg)]

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On 07/27/2015 03:26 PM, William Hubbs wrote:
> All,
>
> I have been looking over this bug for some time attempting to find
> a good solution [1].
>
> The original proposal is to add a "want" dependency which would
> work like "need" but would not fail if the services wanted did not
> start [2].
>
> I agree that the "want" dependency is a valid feature request.
> However, I believe there is a better way to handle the issue in the
> original bug. Basically, I want to follow the suggestion in this
> bug instead [3].
>
> My concern about the original proposal is that it will make
> netmount try to start all daemons that handle file systems, whether
> or not they are actually necessary.
>
> The proposal in [3], on the other hand, is to create a mount script
> that works like netifrc. It would mount a single file system, which
> would be determined by the link it was called from, much like how
> netifrc determines which interface to work on.
>
> Some of the advantages of this approach are listed in the bug. Here
> are a few more I can think of.
>
> - it will eliminate some of our incompatibilities with busybox [4]
> [5].
>
> - It will give us honest reports of success or failure with regard
> to mounting file systems (netmount and localmount can't do that).
>
> - Currently, we have to skip over certain file systems that we
> can't unmount during shutdown. With the new approach, if the mount
> script mounts a file system during boot, it will be able to unmount
> the same filesystem during shutdown, so that will eliminate more
> complexity in our mount/unmount handling.
>
> The one down side of the new approach is the migration away from
> netmount and localmount. I I will need to keep them as wrappers for
> a release or two so we can fix all of our other services that have
> dependencies on them.
>
> I'll also work on making the transition as smooth as possible for
> our users. I believe I'll be able to set up the initial symlinks
> for the multiplexed mount script based on fstab contents
> automatically, but I'm not sure about how much more automation I'll
> be able to do. I will automate more as I come across ways to do so,
> and I am open to suggestions for how to do so.
>
> Let me know what you think.
>
> William
>
> [1] https://bugs.gentoo.org/show_bug.cgi?id=537996 [2]
> https://bugs.gentoo.org/show_bug.cgi?id=406021 [3]
> https://bugs.gentoo.org/show_bug.cgi?id=426944 [4]
> https://bugs.gentoo.org/show_bug.cgi?id=468600 [5]
> https://bugs.gentoo.org/show_bug.cgi?id=468604
>
What would a migration be like? For example, I manage filesystems
exclusively through fstab (to my knowledge). Would this be useful for,
say, mounting over the network? What would managing FSes with openrc
look like?

- -- 
Daniel Campbell - Gentoo Developer
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