Re: configuring /var/run with newer autoconf

[Florian Weimer <fweimer at redhat dot com>]

On 04/12/2016 10:41 AM, Åukasz Stelmach wrote:

> > 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.

The traditional use of an automounter is that you have a file system 
directory, such as /mnt, which contains several remote file systems, and 
each one is mounted on demand once you access the path.

Instead, you seem to be using the automounter to mount just a single 
directory.

May I ask what is the reason for delayed mounting of /var?

> > 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.

nscd is only the tip of the iceberg.  Many NSS modules reference paths 
under /var (such as /var/db, /var/run, or /var/lib/sss).

Florian