Problems with binding user mounts

[aakashhemadri]

I am having a technical issue

I have a collection of docker images built into sandbox directories
I use this as a source and for my instance creation.
I then bind some arbitrary empty host folder to the container image. The container path has pre-existing files/folders created as a part of the image during build.
The host folder overwrites the container path, essentially mounting an empty folder unlike the expected union the docker runtime performs, causing the runscript to fail as scripts in these destination directories are used.

Not sure if I am doing something wrong here or am missing something.

Also can't seem to find documentation on what to do when volumes need to be shared across instances.

Any help is appreciated :)

[dtrudg]

I then bind some arbitrary empty host folder to the container image. The container path has pre-existing files/folders created as a part of the image during build.

This is normal behavior for Singularity. A straight bind mount is used - the directory bound-in will obscure whatever is already present at that location in the container. An overlay is not performed.

Also can't seem to find documentation on what to do when volumes need to be shared across instances.

Singularity differs from Docker in that it does not have a concept of volumes. The container filesystem is a combination of the container content, and direct binds from the host into the container. To share files between instances you would need a directory on the host that is bound into all of the instances.

[aakashhemadri]

Thanks for the clarification @dtrudg