NAME
useradd - Create a new user or update default new user information
SYNOPSIS

useradd [-c comment] [-d home_dir]

[-e expire_date] [-f inactive_time]
[-g initial_group] [-G group[,...]]
[-m [-k skeleton_dir] | -M] [-n] [-o] [-p passwd] [-r]
[-s shell] [-u uid] login
useradd -D [-g default_group] [-b default_home]

[-e default_expire_date] [-f default_inactive]
[-s default_shell]

EXAMPLES Using variables:

$system_command = "/usr/sbin/useradd -u $uid -g $group -c $comment -k $skel_dir -m -d /ip/$account -s /bin/bash $account";

DESCRIPTION

Creating New Users

When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and the default values from the system. The new user account will be entered into the system files as needed, the home directory will be created, and initial files copied, depending on the command line options. The version provided with Red Hat Linux will create a group for each user added to the system, unless the -n option is given. The options which apply to the useradd command are:

-c comment
The new user's password file comment field.
-d home_dir
The new user will be created using home_dir as the value for the user's login directory. The default is to append the login name to default_home and use that as the login directory name.
-e expire_date
The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.
-f inactive_days
The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.
-g initial_group
The group name or number of the user's initial login group. The group name must exist. A group number must refer to an already existing group. The default group number is 1 or whatever is specified in /etc/default/useradd.
-G group,[...]
A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. The default is for the user to belong only to the initial group.
-m
The user's home directory will be created if it does not exist. The files contained in skeleton_dir will be copied to the home directory if the -k option is used, otherwise the files contained in /etc/skel will be used instead. Any directories contained in skeleton_dir or /etc/skel will be created in the user's home directory as well. The -k option is only valid in conjunction with the -m option. The default is to not create the directory and to not copy any files.
-M
The user home directory will not be created, even if the system wide settings from /etc/login.defs is to create home dirs.
-n
A group having the same name as the user being added to the system will be created by default. This option will turn off this Red Hat Linux specific behavior.
-o
Allow create user with duplicate (non-unique) UID.
-p passwd
The encrypted password, as returned by crypt(3). The default is to disable the account.
-r
This flag is used to create a system account. That is, a user with a UID lower than the value of UID_MIN defined in /etc/login.defs and whose password does not expire. Note that useradd will not create a home directory for such an user, regardless of the default setting in /etc/login.defs. You have to specify -m option if you want a home directory for a system account to be created. This is an option added by Red Hat.
-s shell
The name of the user's login shell. The default is to leave this field blank, which causes the system to select the default login shell.
-u uid
The numerical value of the user's ID. This value must be unique, unless the -o option is used. The value must be non-negative. The default is to use the smallest ID value greater than 99 and greater than every other user. Values between 0 and 99 are typically reserved for system accounts.

If no options are specified, useradd displays the current default values.

NAME
usermod - Modify a user account SYNOPSIS

usermod [-c comment] [-d home_dir [-m]]

[-e expire_date] [-f inactive_time] 
[-g initial_group] [-G group [,...]] 
[-l login_name] [-p passwd] 
[-s shell] [-u uid [-o]] [-L|-U] login

DESCRIPTION

The usermod command modifies the system account files to reflect the changes that are specified on the command line. The options which apply to the usermod command are:
-c comment
The new value of the user's password file comment field. It is normally modified using the chfn(1) utility.
-d home_dir
The user's new login directory. If the -m option is given the contents of the current home directory will be moved to the new home directory, which is created if it does not already exist.
-e expire_date
The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.
-f inactive_days
The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.
-g initial_group
The group name or number of the user's new initial login group. The group name must exist. A group number must refer to an already existing group. The default group number is 1.
-G group,[...]
A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. If the user is currently a member of a group which is not listed, the user will be removed from the group
-l login_name
The name of the user will be changed from login to login_name. Nothing else is changed. In particular, the user's home directory name should probably be changed to reflect the new login name.
-p passwd
The encrypted password, as returned by crypt(3).
-s shell
The name of the user's new login shell. Setting this field to blank causes the system to select the default login shell.
-u uid
The numerical value of the user's ID. This value must be unique, unless the -o option is used. The value must be non-negative. Values between 0 and 99 are typically reserved for system accounts. Any files which the user owns and which are located in the directory tree rooted at the user's home directory will have the file user ID changed automatically. Files outside of the user's home directory must be altered manually.
-L
Lock a user's password. This puts a '!' in front of the encrypted password, effectively disabling the password. You can't use this option with -p or -U.
-U
Unlock a user's password. This removes the '!' in front of the encrypted password. You can't use this option with -p or -L.

NAME

     userdel - Delete a user account and related files  

SYNOPSIS

     userdel [-r] login  

DESCRIPTION

The userdel command modifies the system account files, deleting all entries that refer to login. The named user must exist. The options which apply to the userdel command are:

     -r

Files in the user's home directory will be removed along with the home directory itself and the user's mail spool. Files located in other file systems will have to be searched for and deleted manually.