Binding a writable directory in singularity

Question

I'm trying to setup a singularity container for an image processing application, and I need it to be able to save images to a specified directory. I had originally tried using a straight -B flag, but that seems to mount a directory as read only if the container wasn't being run as root. Is there a way to either make a bind r/w for any user, or would I need to use some sort of scratch directory or fusemount?

Answer 1

The write permissions for the bound directory match those on the host system. If you want anyone to be able to write to a given directory, set permissions on the host with chmod 777 dir_name. Keep in mind this will allow anyone to read, write and delete files in the directory. Consider adding users to a shared group and using group permissions (chmod g+rwX dir_name) if there are people using the server who should not have access.

If the directory has the right permissions but you still can't write to it when it's bound, you may want to use singularity --debug exec ... to see that everything is being correctly bound to the container.