Sometimes an error like the following occurs by invoking singularity build with qrsh.
INFO: Starting build...
FATAL: While performing build: conveyor failed to get: error getting username and password: error reading JSON file"/run/user/0/containers/auth.json": open /run/user/0/containers/auth.json:permission denied
As a workaround, do the following after qrsh:
unset XDG_RUNTIME_DIR
and then do singularity build
2020/12/03 update:
Unsetting XDG_RUNTIME_DIR is now done by the job scheduler, therefore the above is no longer required.