User names, UIDs, and GIDs should be unique within your organization, which might span multiple domains.
Keep the following guidelines in mind when creating user or role names, UIDs, and GIDs:
Even though user names can include a period (.), underscore (_), or hyphen (-), using these characters is not recommended because they can cause problems with some software products.
System accounts – Do not use any of the user names, UIDs, or GIDs that are contained in the default /etc/passwd and /etc/group files. Do not use the UIDs and GIDs, 0-99. These numbers are reserved for allocation by the Oracle Solaris OS and should not be used by anyone. Note that this restriction also applies to numbers not currently in use.
For example, gdm is the reserved user name and group name for the GNOME Display Manager daemon and should not be used for another user. For a complete listing of the default /etc/passwd and /etc/group entries, see Table 4–6 and Table 4–7.
The nobody and nobody4 accounts should never be used for running processes. These two accounts are reserved for use by NFS. Use of these accounts for running processes could lead to unexpected security risks. Processes that need to run as a non-root user should use the daemon or noaccess accounts.
System account configuration – The configuration of the default system accounts should never be changed. This includes changing the login shell of a system account that is currently locked. The only exception to this rule is the setting of a password and password aging parameters for the root account.