User and Group Related Commands

# chage -E 2005-12-31 user1   
set deadline for user password

# groupadd [group-name]   
create a new group

# groupdel [group-name]   
delete a group

# groupmod -n moon sun   
rename a group from moon to sun

# grpck   
check correct syntax and file format of '/etc/group' and groups existence

# newgrp - [group-name]   
log into a new group to change default group of newly created files

# passwd   
change password

# passwd user1   
change a user password (only by root)

# pwck   
check correct syntax and file format of '/etc/passwd' and users existence

# useradd -c "User Linux" -g admin -d /home/user1 -s /bin/bash user1   
create a new user "user1" belongs "admin" group

# useradd user1   
create a new user

# userdel -r user1   
delete a user ( '-r' eliminates home directory)

# usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1   
change user attributes