# Containers on Perlmutter

- `podman-hpc` vs `shifter`

- Differences (env, volume mounts, swapped modules, and image caching)

- Best practices of running containers
- proper storage system to use
- Containers per task vs containers per node
- A deeper view at library swapping, looking at `.conf` files under `/etc/podman_hpc/` and `/etc/podman_hpc/modules.d`
- GPU
- MPI
- other modules
- `cvmfs`, `nccl`, `openmpi-pmi2` `openmpi-pmix` etc
- skip library swapping with shifter (`--module=none`)
- Share images with other users without pushing to registry

## local image sharing on CFS

podman-hpc --squash-dir /path/to/shared/area/on/cfs migrate ubuntu:latest
chmod -R a+rx  /path/to/shared/area/on/cfs

Other users

export PODMANHPC_ADDITIONAL_STORES=/path/to/shared/area/on/cfs
podman-hpc images

## Running noVNC on login node for GUI apps

Ref: [dingpf/nvidia-noVNC](https://github.com/dingp/nvidia-noVNC)

The example dockerfile with

### Start the container on one login node

Generate a VNC password file.

podman-hpc run --rm -it -v $HOME:/scratch --entrypoint=/bin/bash docker.io/dingpf/novnc-nvidia:latest
# inside the container, run 
vncpassword
# once finished
cp ~/.vnc/passwd /scratch/.vnc_passwd

Run the container on the login node.

podman-hpc run \
	--gpu \
	--rm -d -p 6080:6080 \
	--name ubuntu2204-novnc \
	-v <software_dirs_on_global_common>:<path_in_container> \
    -v ~/.vnc_passwd:/root/.vnc/passwd
	dingpf/novnc-nvidia:latest

Note that if someone else is using port `6080` on the login node, you may need to change the first `6080` in `-p 6080:6080` to another free port.

### Setting up a SSH tunnel to the login node

# change ~/.ssh/nersc if the path to your nersc identity file is different
# change loginXX to the hostname of the login node where you have your container running
ssh -o IdentitiesOnly=yes \
    -o IdentityFile=~/.ssh/nersc \
    -J perlmutter.nersc.gov \
    -L 6080:localhost:6080 loginXX -N -f

### Access noVNC in a browser

You should now be able to go to `localhost:6080` in a browser window. The default noVNC password is `00000000`.