Aliases
An alias is an optional alternate name for a primary name. Aliases can be assigned to principals and groups, but not to organizations. Aliases and the primary name for which they are an alternate share the same UUID and UNIX ID. (UUIDs and UNIX IDs are described in Universal Unique Identifiers and UNIX IDs.) An alias is a key field that you can use to query the registry database.
Because you can create one account for each primary name and each alias, aliases give you the flexibility to establish several accounts for the same principal. For example, assume that for the primary name mahler you create three aliases: gustav, gus, and gm. You can then create four accounts for the principal mahler: one for the primary name and one for each of the name's aliases. The accounts can use different home directories and passwords and can be associated with different groups and organizations.
Because principals accrue only the rights that are associated with the primary name or the alias that they log in with, these multiple accounts for the same person accommodate different access patterns. For example, mahler may be a member of the composers group and gustav can be a member of the music_admin group, which is a group of system administrators. The principal mahler logs in as mahler to perform day-to-day tasks and as gustav to perform administrative duties. To help prevent accidental damage to the system, it is a good idea to set up accounts so that users can log into an account with the least privileges necessary to perform their tasks.
For groups, aliases are useful if you want to associate two group names with the same UNIX number.
See Creating and Maintaining Aliases for Principals or Groups for information on creating aliases.