The document discusses adding, modifying, and deleting users and groups in Linux. It explains that the root user can create, modify, and delete other users and groups. Users are added with the useradd command, modified with usermod, and deleted with userdel. Groups are added with groupadd, modified with groupmod, and deleted with groupdel. Users can be added to existing groups using usermod. Relevant user and group information is stored in /etc/passwd, /etc/shadow, /etc/group, and /etc/gshadow files. Errors during user/group management may be caused by lock files that need to be deleted.

1. Name Engr. Zardari Saddam Hussain
B.E Computer System Engineering QUEST Nawabshah
HIST ID 2374
Training System & Network Administration
Shift Evening(1:30 PM - 6:30 PM)
Institute Hidaya Institute of Science And Technology Jamshoro, Sindh
[zardarisaddam@hist~]$ whoami

3. Topic for discussion
All in LINUX
1 ) Users
i. Adding user
ii. Deletion of user
iii. User Modification
2 ) Groups
i. Adding Group (s)
ii. Deletion of Group(s)
iii. Addition of users in Existing Group
3) Errors During Creation of Users and Groups

4. Caution…..!
 In order to create new logins, modify or delete users & groups,
you must already be logged in as root.

5. Why Users are Created….?
Because…
 There are number of Persons in an Organization and everyone have to access
his own account
 For Security purposes.
Why groups are Created….?
Because…
 To setup same type of users in a single group/category so that we may easily
assign permissions to user ,in Group.

6. Users
User 1 User 2 User 3

7. Addition of User
Make sure that you are in ROOT……???
To add new users just use this command
[root]# useradd abulaqdeerkhan
User is added
Don’t try to write user name in upper case either you will face
error
User name and primary groups is stored in /etc/passwd.

8. Setting Password of user
To give a password to this user which we created before remember you
are in root ,just type
[root]# passwd abulaqdeerkhan
If abulaqdeerkhan wants to change his own password than he must be
logged in his account and just type
[abulaqdeerkhan] $ passwd
Enter existing password
Enter new password
Enter new password again (to validate)
Passwords for each user is stored in /etc/shadow.
This file should only be changed using the passwd command.

9. By default Home directory of every new user is created in /home
but if you want to create user’s home directory to any other
location than you can do that using this command.
[root]# useradd abulaqdeerkhan –d / abulaqdeerkhan
Now home directory of user abulaqdeerkhan by this name will be
in / (root) instead of /home.

10. Removing a User
Once user is created than it can be deleted, any time you want
to do this just type this command.
[root]# userdel abulaqdeerkhan
When a user is deleted by default its files remains in home, because
these files may contain important data.
But if you want to remove their home folder and all their files.
[root]# userdel -r abulaqdeerkhan

11. What do you mean By Modification…..??
To change the structure, character, intent, etc.
To make change in Existing Things

12. This is Modification……..!!!

13. Same concept of modification here in Linux
To Modify the Existing User
Particular Command is used to Modify the users
[root] # usermod
You can Use this command To..
Add an Expiry Date on Existing User
Change Login Name
Change Group
Lock user account
Unlock user account

14. Change Expiry date of Existing user
[root] # usermod -e 20120630 amarjaleel
User amarjaleel’s account will be Expired on 30 June 2012
Change Login Name
[root] # usermod -l jaleelsindhi ( New Name) amarjaleel (Old Name)
New login name is jaleelsindhi
Lock user account
[root] # usermod -L quaideazam
User quaideazam’s account is now locked

15. Unlock user account
[root] # usermod -U allamaiqbal
User allamaiqbal’s account is now unlocked

16. How To know about Locked and Unlocked Accounts
Go To
[root] # vim /etc/shadow
If exclamation mark ( ! ) in front of the password appeared means
particular account is Locked
When (!) mark vanished out means account is Unlocked
Note:
When account is locked user cannot login Graphically or
from command line

17. Groups

18. Addition of Group(s)
Here we are going to Add a New Group
So don’t forget to be in ROOT
[root]# groupadd eagles5
Here new group eagle5 is added
Lets Set group password
[root]# gpasswd eagles5
Go to..
/etc/gshadow to se the information of group password

19. Deletion of Group(s)
Here we are going to remove a n existing Group
[root]# groupdel eagles5
Here group eagle5 is deleted
Go to..
/etc/group to se the information of group

20. Adding user(s) to Group(s)
 adding users to existing group
[root]# usermod -G eagles5(group name) sheikhayaz(user
name)
Here sheikhayaz is added to group eagles5 .
Remember that when a new user is created his primary group by
its user name also created, now sheikhayaz has eagle5
(supplementary group) but now his primary groups is eagle5,
sheikhayaz (primary group) but here changed Now……
Go to..
/etc/group to se the information of group

21. Adding user(s) to Group(s)
 adding users to existing group
[root]# usermod -g eagles5(group name) riazudinsiddiqui(user name)
Here riazudinsiddiqui is added to group eagles5 and he will have only one
group that is eagles5
Now members of eagle5 group are free to access and modify all of its
contents without any restriction,its setting up its initial group
Go to..
/etc/group to se the information of group

22. Adding multiple users to a Group
 adding multiple users to existing group
[root]# gpasswd -M ali, saddam, qadir ,unis ,nbgabol eagle5(group name)
Here all five users are added to a single group eagles5
By using this command you may add many users as you can
Go to..
/etc/group to se the information of group

23. Errors During Creation of Users and Groups
 some times errors are arise during creation of users and groups, because
of these file which are automatically created in /etc
/etc/shadow.lock
/etc/gshadow.lock
/etc/passwd.lock
/etc/group.lock
You just have to remove these files from /etc than you will be able to
create users and accounts and their passwords
[root]# rm -rf /etc/shadow.lock
And all other
These files may be created due to giving incorrect password many times,
for security reasons LINUX locks such users and groups

24. [zardarisaddam@hist~]$ man summary
Root can create users and groups
There is a difference between adding a user and modifying a user
Whenever a new user is added its primary group is created by default
A file /etc/passwd contain the information such as User ID, group ID,
homedir etc. The format is like this.
user:x:UID:GID:comment:homedir:shell
e.g.
root:x:0:0:root:/bin/bash
So as you can see there is a lot of things stored in /etc/passwd
 A file /etc/group contains information regarding groups
 A file /etc/shadow contains passwords in encrypted form
 A file /etc/gshadow contains passwords of groups in encrypted form
if errors are arising during creation of groups and users are faced by
deleting files
/etc/shadow.lock
/etc/gshadow.lock
/etc/passwd.lock
/etc/group.lock

25. [zardarisaddam@hist~]$ kill -9 2374