Re: configuring /var/run with newer autoconf

[Åukasz Stelmach <l dot stelmach at samsung dot com>]

It was <2016-04-11 pon 18:09>, when Florian Weimer wrote:
> On 04/11/2016 09:20 AM, Åukasz Stelmach wrote:
>> It was <2016-04-08 piÄ 14:31>, when Florian Weimer wrote:
>>> On 04/08/2016 09:52 AM, Åukasz Stelmach wrote:
>>>
>>>>> but you also have another option and what most people have been
>>>>> doing: c) symlink /var/run to /run
>>>>
>>>> This does not help to avoid deadlocks at all.
>>>
>>> Why?  It may need changes to autofs, so that it can produce the
>>> required symbolic link, at an early stage of operation.
>>
>> autofs works as expected, it does not provide any contents itself, instead it
>> intercepts all requests and put them on hold until the actual filesystem
>> is mounted. I wouldn't expect anything else.
>
> For generating the symlinks in /var, I would expect to provide them.
>
> Are you trying to automount /var itself, or is /var a directory
> monitored by the automounter?

I don't exactly understand the alternative. Let me try to describe what
happens in my system.

I've got a root fs. There is the /var directory. It is empty. There is

    LABEL=var    /var    ext4    defaults,noatime,x-systemd.automount    0 2

line in my fstab. x-systemd.automount tells systemd to mount autofs
under /var, start monitoring it for requests and mount the real ext4
file-system when a request comes.

>> I'd say the case we are discussing is an extremely rare corner case for
>> autofs and I'd rather expect requirement for autoconf 2.70 be accepted
>> in libc (-; before any kernel developer accepts a patch for autofs.
>
> It's not just autoconf (which, as far as I understand it, is not
> released at this point).   The pathname is part of the ABI, so we
> can't really change it for existing architectures.

I am not sure this is actually true. What is a part of ABI (as far as I
understand it) is _PATH_VARRUN defined in sysdeps/generic/paths.h and
sysdeps/unix/sysv/linux/paths.h. However, this isn't what nscd
uses. nscd has its own definitions in nscd/nscd-client.h and nscd/nscd.h
which apparently are not exported to /usr/include and are not supposed
to be used outside nscd. That means it should be possible to change the
the location wher nscd keeps its stuff without breaking ABI.

-- 
Åukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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