File Format
The format of the entries in file group_override is similar to the format of the entries in the UNIX group file. This format is
group_name:passwd:group_uid:members
In this entry, group_name and group_uid are keyfields. You must enter one to identify the group to which the override applies. The keyfield is used to perform a lookup in the override file when you use the passwd_export command. The lookup is performed in order as the entries are specified in an override file: first by group name, then by group UNIX ID. If you specify both keyfields in an override entry, the group name is used as the lookup key; subsequent fields are used as overrides.