Re: [PATCH 2/2] Configure custom layers via environment variables

[Vivek Goyal <vgoyal@redhat.com>]

On Sun, May 17, 2020 at 11:45:59AM +0300, Amir Goldstein wrote:
> > >
> > > What's most intuitive to me is this.
> > >
> > > - If user only specifies UNIONMOUNT_BASEDIR, all layers (lower, upper,
> > >   work and even mount point) comes from that directory.
> >
> > OK.
> >
> > >
> > > - If user specifies both UNIONMOUNT_LOWERDIR and UNIONMOUNT_BASEDIR, then
> > >   lower layer path comes from UNIONMOUNT_LOWERDIR and rest of the layers
> > >   come from UNIONMOUNT_BASEDIR.
> >
> > DONE.
> >
> > >
> > > - If user specifies UNIONMOUNT_MNTPOINT, it is used as overlay mount
> > >   point. Otherwise one is selected from UNIONMOUNT_BASEDIR if user
> > >   specified one. Otherwise "/mnt" is the default.
> > >
> >
> > OK.
> >
> 
> Vivek,
> 
> I finally got around to implementing your suggestion (see [1]).
> 
> Quoting from README:
> 
>      When user provides UNIONMOUNT_LOWERDIR:
> 
>      1) Path should be an existing directory whose content will be deleted.
>      2) Path is assumed to be on a different filesystem than base dir, so
>         --samefs setup is not supported.
> 
>      When user provides UNIONMOUNT_BASEDIR:
> 
>      1) Path should be an existing directory whose content will be deleted.
>      2) If UNIONMOUNT_MNTPOINT is not provided, the overlay mount point will
>         be created under base dir.
>      3) If UNIONMOUNT_LOWERDIR is not provided, the lower layer dir will be
>         created under base dir.
>      4) If UNIONMOUNT_LOWERDIR is not provided, the test setup defaults to
>         --samefs (i.e. lower and upper are on the same base fs).  However,
>         if --maxfs=<M> is specified, a tmpfs instance will be created for
>         the lower layer dir.

Hi Amir,

Do you want to mention a word upper dir also when UNIONMOUNT_BASEDIR. That
is upperdir is also created under UNIONMOUNT_BASEDIR. IOW, all directories
lower, upper and mount point are under UNIONMOUNT_BASEDIR (until and
unless overridden by other environment variables).

For point 4, I understand that we will mount multiple instances of
tmpfs because maxfs tests on multiple different filessytems. I am
assuming that we will be creating lowerdir mount points under
UNIONMOUNT_BASEDIR for --maxfs.

I think this looks pretty good. Just one more thing. Is there a way to
specify multiple lowerdirs as well. If not, may be in future we can
add it once somebody needs to specify multiple lowerdirs.

Thanks
Vivek

> ----
> 
> I realize this last item (4) is a bit tricky.
> Let me know if you think it needs further clarification.
> 
> Thanks,
> Amir.
> 
> 
> [1] https://github.com/amir73il/unionmount-testsuite/commits/envvars
>