External resources

An resource is called "external", if it can't be dumped and restored without external help. Usually this mean that a part of it state is out of a dumped container.

The general approach is to enumerate all such resources on dump and set one of restoring strategies for each of them on restore. An approach how to restore an resource may be different for different types of resources.

• External bind mounts
• External files
• External UNIX socket

All of them are controlled with the --external ID option.