What is the difference between the default configuration for zones and an immutable zone?

Note:

*Immutable Zones provide read-only file system profiles for solaris non-global zones.

*A zone with a read-only zone root is called an Immutable Zone. A solaris Immutable Zone preserves the zone's configuration by implementing read-only root file systems for non-global zones. This zone extends the zones secure runtime boundary by adding additional restrictions to the runtime environment. Unless performed as specific maintenance operations, modifications to system binaries or system configurations are blocked.