USER MANAGEMENT BASICS

HERE I AM INTRODUCING SOME USER COMMAND AND THEIR USE IN OUR
DAILY USER ADMINISTRATION

useradd - for adding users to your linux machine

syntax : useradd -[option] [$username]

the main options are as listed below with a example.

useradd -u 508 -d /var/user1 -s /bin/bash newuser

create a user named newuser with uid 508 ,home directory /var/user1 and default shell as /bin/bash

useradd -M newuser4 

create a user named newuser4 without creating a home directory for the user

useradd -N newuser5

create a user named newuser5 without creating a private group for the user

useradd -r newuser6 

create a system user ie uid below 500

useradd -e 2013-12-05 newuser1

create a user named newuser1 with expire date 05-12-2013

useradd -g ftp newuser2

create a user named newuser2 with default group as ftp here instead of group name we can also use 

the gid of the perticular group

useradd -G ftp,root newuser3

create a user named newuser3 with primary group newuser3 and secondry groups root,ftp

usermod -Command used for modifying the user parameters.

syntax : usermod -[option] [$user]

the above mentioned options (ie useradd options) can also used with usermod

userdel : Command for deleting user

syntax : userdel -[option] [$user]

userdel without option will delete the user but it will not delete the home directory for the user for that we have to use -r option

userdel -r newuser3

this command remove newuser3 as well as its home directory

groupadd - Command used for adding a group

syntax : groupadd -[options] [$groupname]

here is some examples 

groupadd -g 567 newgroup

create a group named newgroup with gid 567

groupmod -Command for modifying group parameter 

groupdel - Command for removing a group 

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