Installation guide

and enhanced security. The commands are documented in the following
reference pages: useradd
(8), usermod(8), userdel(8), groupadd(8),
groupmod
(8), and groupdel(8).
• The adduser and addgroup utilities, documented in adduser
(8) and
addgroup
(8). These utilities provide simple, interactive scripts you can
use to add new user accounts and groups. These utilities can be used
only on systems that do not use NIS.
• The vipw utility, documented in vipw
(8), allows you to invoke an editor
in order to edit the password file manually. You can use the utility to
edit the local password database, but you cannot use it to edit the NIS
database. Additionally, you cannot use the vipw utility on systems that
have enhanced security. The vipw command allows you to edit the
passwd file and at the same time locks the file to prevent others from
modifying it. This command also does consistency checks on the
password entry for root and does not allow a corrupted root password to
be entered into the passwd file.
9.1.4 UIDs and GIDs
Each user is known to the system by a unique number called a user
identifier (UID). The system also knows each user group by a unique
number called a group identifier (GID). The system uses these numbers to
track user file access permissions and group privileges and to collect user
accounting statistics and information.
The maximum number of UIDs and GIDs allowed is 2,147,483,647 (31
bits). This does not mean that 2.14 million users can simultaneously log
onto a system; rather, it means that 2,147,483,647 user and group
identifiers are available. The maximum number of users that can be logged
on is determined by the available system resources. To preserve strict
binary compatibility with legacy applications, the new limits are not
enabled by default in this release.
9.1.4.1 Enabling or Disabling Extended UID and GID Support
By default, extended UIDs are not enabled in the kernel. To enable this
feature, you use sysconfig or the dxkerneltuner interface to set the
value of variable enable_extended_uids to 1 (enabled). Note that when
extended UIDs and GIDs are disabled, files owned by a user with an
extended UID or GID will be inaccessible to all users except root. Any user
with an extended UID or GID will not have access to log in to the system
or use the su command to access their accounts.
To enable or disable extended UID and GID support, do the following:
1. Become the root user (use the su command)
Administering User Accounts and Groups 9–5