If the bundle has a primitive, the primitive’s resource agent may want to set node attributes such as promotion scores. However, with containers, it is not apparent which node should get the attribute.

If the container uses shared storage that is the same no matter which node the container is hosted on, then it is appropriate to use the promotion score on the bundle node itself.

On the other hand, if the container uses storage exported from the underlying host, then it may be more appropriate to use the promotion score on the underlying host.

Since this depends on the particular situation, the container-attribute-target resource meta-attribute allows the user to specify which approach to use. If it is set to host, then user-defined node attributes will be checked on the underlying host. If it is anything else, the local node (in this case the bundle node) is used as usual.

This only applies to user-defined attributes; the cluster will always check the local node for cluster-defined attributes such as #uname.

If container-attribute-target is host, the cluster will pass additional environment variables to the primitive’s resource agent that allow it to set node attributes appropriately: CRM_meta_container_attribute_target (identical to the meta-attribute value) and CRM_meta_physical_host (the name of the underlying host).