Critical file systems 

Critical file systems are required by the Solaris OS. These file systems are separate mount points in the vfstab of the active and inactive boot environments. These file systems are always copied from the source to the inactive boot environment. Critical file systems are sometimes referred to as nonshareable.

Examples are root (/), /usr, /var, or /opt.

Shareable file systems 

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.

/export is an example of a file system that can be shared.

For more detailed information about shareable file systems, see Guidelines for Selecting Slices for Shareable File Systems.

Swap 

• For UFS file systems, swap is a special shareable volume. 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.

• For ZFS file systems, swap and dump volumes are shared within the pool.

• For procedures about reconfiguring swap for UFS file systems, see To Create a Boot Environment and Reconfiguring Swap.

• For information about swap for ZFS root pools, see System Requirements and Limitations When Using Solaris Live Upgrade