System Administration Guide: Devices and File Systems

Swap Areas and the /etc/vfstab File

After the system is installed, swap slices and swap files are listed in the /etc/vfstab file. They are activated by the /sbin/swapadd script when the system is booted.

An entry for a swap device in the /etc/vfstab file contains the following:

The file system that contains a swap file must be mounted before the swap file is activated. So, in the /etc/vfstab file, ensure that the entry that mounts the file system comes before the entry that activates the swap file.