/etc/adduser.conf (5) [adduser.conf] - configuration file for adduser(8) and addgroup(8) .
/etc/deluser.conf (5) [deluser.conf] - configuration file for deluser(8) and delgroup(8) .
addgroup (8)         - add a user or group to the system
adduser (8)          - add a user or group to the system
adduser.conf (5)     - configuration file for adduser(8) and addgroup(8) .
bsd-write (1)        - send a message to another user
chage (1)            - change user password expiry information
check_driver (1)     - Linux 2.6(.16+) userspace device rebinding helper.
chfn (1)             - change real user name and information
crontab (1)          - maintain crontab files for individual users (V3)
defoma-user (1)      - Debian Font Manager for users
delgroup (8)         - remove a user or group from the system
deluser (8)          - remove a user or group from the system
deluser.conf (5)     - configuration file for deluser(8) and delgroup(8) .
environ (7)          - user environment
fuser (1)            - identify processes using files or sockets
futex (4)            - Fast Userspace Locking
futex (7)            - Fast Userspace Locking
group (5)            - user group file
groups (1)           - print the groups a user is in
hosts.equiv (5)      - list of hosts and users that are granted "trusted"r command access to your system
id (1)               - print user identity
intro (1)            - Introduction to user commands
last (1)             - show listing of last logged in users
lastb (1)            - show listing of last logged in users
lastlog (8)          - reports the most recent login of all users or of a given user
logname (1)          - print user's login name
netlink (7)          - Communication between kernel and userspace (PF_NETLINK)
newusers (8)         - update and create new users in batch
nologin (5)          - prevent non-root users from logging into the system
passwd (1)           - change user password
PF_NETLINK (7)       - Communication between kernel and userspace (PF_NETLINK)
readline (3readline) - get a line from a user with editing
su (1)               - change user ID or become super-user
sudo (8)             - execute a command as another user
sudoedit (8)         - execute a command as another user
sudoers (5)          - list of which users may execute what
sulogin (8)          - Single-user login
tasksel (8)          - a user interface for installing tasks
telnet (1)           - user interface to the TELNET protocol
telnet.netkit (1)    - user interface to the TELNET protocol
ucf (1)              - Update Configuration File: preserve user changes in configuration files
udp (7)              - User Datagram Protocol for IPv4
unix_chkpwd (8)      - check the password of the invoking user
useradd (8)          - create a new user or update default new user information
userdel (8)          - delete a user account and related files
usermod (8)          - modify a user account
users (1)            - print the user names of users currently logged in to the current host
wall (1)             - write a message to users
whoami (1)           - print effective userid
write (1)            - send a message to another user
xset (1)             - user preference utility for X