Error in Blitz-0.log:
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name '/OMERO/Pixels' defined in URL [jar:file:/opt/omero/server/OMERO.server-5.6.17-ice36/lib/server/omero-server.jar!/ome/services/service-ome.io.nio.PixelsService.xml]: Cannot resolve reference to bean 'backOff' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'backOff' defined in URL [jar:file:/opt/omero/server/OMERO.server-5.6.17-ice36/lib/server/omero-server.jar!/ome/services/service-ome.io.nio.PixelsService.xml]: Bean instantiation via constructor failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [ome.io.nio.SimpleBackOff]: Constructor threw exception; nested exception is java.lang.RuntimeException: javax.imageio.IIOException: Can't create cache file!

This seems to be caused by ome/openmicroscopy#6441 which assumes the OMERO.server/var/tmp/ directory exists. Older versions of OMERO.server automatically created all necessary sub-directories (log, master, registry) under OMERO.server/var/ if it's empty (e.g. mounted as an empty volume) but tmp isn't created.

ome/openmicroscopy#6448