Use cases for multiple uid mapping?

[Eric W. Biederman]

We had a discussion in the hackroom at LPC talking about use cases for
a shiftfs style setup where there are different mappings of uids to
disk.

In the discussion we had a couple of ideas of kernel developments
we should look at that address some of these.

- Fix rlimits in user namespaces (This potentially allows multiple
  containers to run with the same userids simplifying the mapping
  problem).

- Look at extending kuid_t to 64bits and using the highbits to
  implement uids that are private to user namespaces and don't
  map out.
  
- Look at ways for allowing setgroups unprivileged.


Together this has the potential that the existing uid & gid mappings
will be able to function the same as the proposed fusid mappings. Fingers crossed.


I had some problems with audio and a lot of people were talking
quickly.  So I did not manage to capture everyone's use cases.   And I
definitely was not able to see how everyone's use cases interacted with
the changes we are looking at.

I know for certain I missed Serge's usecase (apologies).

Can people follow up to this and report their use cases?

There are some real challenges and I would like to see if we
can solve them, while avoiding scary problems like changing
uids on write.

Eric