Solaris 10 uses a UID (User ID) to identify each user account. The UID is a unique number assigned to each user. It is usually assigned by the operating system when the account is created. It may be necessary to modify or change a user’s UID so in order to allow the user to access a particular program or another operating systems in a network. The “usermod” command is used to change a user’s UID.

How to Modify a UID in Solaris 10 - 58