Add mounts role with /tmp defaulted to tmpfs on login & compute nodes

[sjpb]

• Adds a mounts role to support arbitrary mounts via fstab, with compute_init support.
• mounts role enabled by default for compute and login nodes.
• Role defaults to moving /tmp to a tmpfs of 10% of RAM. This prevents users from filling the root disk.

Note that the tmpfs functionality is actually provided by the systemd tmp.mount unit (masked by default in RockyLinux genericcloud images). However this is automatically triggered by appropriate changes to fstab, and using Ansible's posix.mount module to drive it is is much easier to integrate correctly than via overrrides using the current systemd unit. It also allows for a more general solution for additional mount-points which can evolve towards #814. Testing shows changes to the tmpfs size are correctly applied by re-running Ansible.

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/20995934106

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/20996758279

[elelaysh]

Would it make sense to have a more granular enable/disable?
By adding mount_tmp_enable: true and handling an enable field in a mounts dict value (can be | default(True))

[sjpb]

Would it make sense to have a more granular enable/disable? By adding mount_tmp_enable: true and handling an enable field in a mounts dict value (can be | default(True))

Yeah that's exactly the sort of discussion I was expecting/after, thanks. I was wondering about removing the entire tmp mount dict with a flag like that, but actually a generic enable field is maybe better. It lets you have different mounts on different hosts (using something like enable: "{{ 'name' in group_names }}". Without that you have to get into using non-all group_vars which is really nasty with multiple environments.

I'll try that, thanks.

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/21027912410

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/21028175460

[elelaysh]

LGTM

[elelaysh]

LGTM