Modify user account information.
SYNTAX usermod [options] [user] OPTIONS -c comment Comment field. -d dir Home directory. -e date Account expiration date. date is in the format MM/DD/YYYY. Two-digit year fields are also accepted. The value is stored as the number of days since January 1, 1970. This option requires the use of shadow passwords. -f days Permanently disable account this many days after the password has expired. A value of -1 disables this feature. This option requires the use of shadow passwords. -g group Initial group name or ID number. If a different default group has not been specified using the -D option, -G groups Supplementary groups given by name or number in a comma-separated list with no whitespace. The user will be removed from any groups to which they currently belong that are not included in groups. -l name Login name. This cannot be changed while the user is logged in. -o Override. Accept a nonunique uid with the -u option. (Probably a bad idea.) -s shell Login shell. -u uid Numerical user ID. The value must be unique unless the -o option is used. The default value is the smallest ID value greater than 99 and greater than every other uid.
userdel [-r] user - Remove user and (optionally) the user's home directory
useradd - add user account