Solaris Live Upgrade distinguishes between two file system types: critical file systems and shareable file systems. Critical file systems are required by the Solaris operating environment and are separate mount points in the vfstab of the active and inactive boot environments. Examples are root (/), /usr, /var, or /opt. These file systems are always copied from the source to the inactive boot environment. Critical file systems are sometimes referred to as non-shareable. Shareable file systems are user-defined files such as /export that contain the same mount point in the vfstab in both the active and inactive boot environments. Therefore, updating shared files in the active boot environment also updates data in the inactive boot environment. When you create a new boot environment, shareable file systems are shared by default. But you can specify a destination slice and then the file systems are copied. For more detailed information on shareable file systems, see Guidelines for Selecting Slices for Shareable File Systems.
Swap is a special circumstance of a shareable file system. Like a shareable file system, all swap slices are shared by default. But, if you specify a destination directory for swap, the swap slice is copied. You achieve this goal by using the character user interface or at the command line by using lucreate(1M) with the -m option. A limitation to splitting and merging swap slices is that the swap slice cannot be in use by any boot environment except the current boot environment or if the -s option is used, the source boot environment. The boot environment creation fails if the swap slice is being used by any other boot environment, whether the slice contains a swap, UFS, or any other file system. A swap slice is not required. For procedures on reconfiguring swap, see “To Create a Boot Environment (Character Interface)” Step 9, or To Create a Boot Environment and Reconfigure Swap (Command-Line Interface).
When you create file systems for a boot environment, the rules are identical to the rules for creating file systems for the Solaris operating environment. Solaris Live Upgrade cannot prevent you from making invalid configurations on critical file systems. For example, you could enter an lucreate command that would create separate file systems for root (/) and /kernel—an invalid division of root (/).