Usage of `/var/tmp/username`

[wihobbs]

Nick Sly gave a presentation to LC this morning about building containers for TOSS 4 and TOSS 5. In this presentation, he mentioned that his development on these containers for Flux was made inconvenient by the fact that Flux requires /var/tmp/username to be mounted from the host of the container, which isn't done by default.

AFAIK we don't do anything in core in /var/tmp/username, although in offline discussion @garlick mentioned that might be an LC configuration that points to where the /tmp/ directory is located, which stores the KVS for the running instance.

Let's see if we can figure out what's going on in /var/tmp/username and, if we can avoid that requirement, maybe we can make building these containers a little easier...

[grondo]

IIRC, LC sets TMPDIR to /var/tmp/username. Flux creates a job tmpdir in TMPDIR. One solution would just be to override the LC TMPDIR for containers.

I'm not sure it is a requirement that TMPDIR exists, but the job shell will warn the user (on every node no less)

Unable to create TMPDIR=/var/tmp/username, resetting TMPDIR=/tmp

And the job shell will then use /tmp for TMPDIR. Maybe we could just silence that warning and the issue would go away?