A device alias, is a shorthand representation of a device path. An alias is a text name identifying a device node by showing its position in the device tree. An alias represents an entire device path, but that path need not refer to a leaf node. Each implementation can have a number of predefined aliases for devices commonly installed on that machine.
For example, the alias disk might represent the complete device path name:
Virtual machines have predefined device aliases for the most commonly used devices, however, you can create, modify, and examine aliases with the devalias command. User-defined aliases are lost after a reset or power cycle, but you can create a persistent alias by storing the devalias command in an NVRAMRC script. For more details, see Create a Device Alias.