Files in Apptainer Containers

Apptainer is designed to work closely with the host filesystem. In most cases, your home directory and current working directory remain accessible from within the container.

Accessing Your Files

While inside a container, check your current directory:

pwd

You can also list files in your home directory:

ls ~

The files and directories you see should match those available outside the container.

note

Files created in these mounted directories remain available after the container exits.

Binding Additional Directories

Sometimes you may need access to directories through a different path inside the container.

Apptainer allows additional directories to be mounted using the -B option:

apptainer shell \
    -B /scratch/<NetID>:/data \
    /share/apps/images/ubuntu-24.04.3.sif

In this example, your scratch directory on the host system is made available as /data inside the container.

After entering the container, you can verify the mount:

ls /data

Any files stored in /scratch/<NetID> on the host system will be accessible through /data inside the container.

The source and destination paths do not need to be the same. This can be useful when an application expects data to be located in a specific directory within the container.

info

Container images are typically read-only. Research data, scripts, notebooks, and output files usually remain outside the container.

By making host directories available inside the container, Apptainer allows applications to access data stored on Torch while maintaining a reproducible software environment.