File system migration refers to the system management operations related to stopping access to a file system, and then restarting these operations to access the file system from a different computer system. File system migration might be required to be done once, such as when permanently migrating a file system to another system without any future desire to move the file system back to its original system or to other systems. This type of file system migration is referred to as one-time file system migration. When ongoing file system migration between multiple systems is desired, this is known as ongoing file system migration. Different actions are required depending on the kind of migration, as described in the following sections.