Chapter 9Managing Users

There are three types of users in linux

System users: ?

Super user: ?

Normal users: ?

Linux users

There are three types of users in linux

System users: (they are the software/applications users created

automatically by the system) e.g mail , MySQL , ftp …..

Super user: ?

Normal users: ?

Linux users

There are three types of users in linux

System users: (they are the software/applications users created

automatically by the system) e.g mail , MySQL , ftp …..

Super user: (the superuser/root user/system administrator is only one, his duties are to install software + create or delete users + look after the system resources ….) the prompt sign of super user is # in all shells .

Normal users: ?

Linux users

There are three types of users in linux

System users: (they are the software/applications users created

automatically by the system) e.g mail , MySQL , ftp …..

Super user: (the superuser/root user/system administrator is only one, his duties are to install software + create or delete users + look after the system resources ….) the prompt sign of super user is # in all shells .

Normal users: (the normal users can me many , the powers of normal users are limited but normal user has full powers in his home directory ) the prompt sign of normal users in $ in bourne shell and % in

c-shell

Linux users

The files which keeps the information of users The passwd file: (etc/passwd) old method file • User name• Password• User id• Group id• User description• User home directory• User shell

Linux users

The files which keeps the information of users The shadow file: (etc/shadow) new method file , most information is encrypted

• User name• Password• User id• Group id• User description• User home dir• User shell

Linux users

Users name + User id bilal + 501humans can memorize + computer can memorize

Group name + group id bilal + 501humans can memorize + computer can memorize

Users and Groups

File permissions

chmod 777 myfile Will assign read, write and execute permissions to

all owner, group and others (rwxrwxrwx)

chown -R ali mydir It will change the ownership of the Directory mydir for

the user ali, -R option will change ownership of the

sub directories residing inside mydir as well.

chgrp -R usman mydir It will change the group ownership of the directory mydir

for the user usman, -R option will change group

ownership of the sub directories residing inside mydir

as well.

File permissions Giving file permissions to files and directories

Command -option argument description

Group Information FileThe files which keeps the information of group The group file: (etc/group) • group name• Password• Group id

Assigning password to more then one userchpasswd username:password

chpasswd umar:abc123 usman:ord4446 zahid:sleep7-6

....:....

Creating a Group groupadd bilal

Removing a Group groupdel bilal

groupmod (to modify a group) useradd –G (to create a fresh user and assign him to a group)

useradd –G bilal billygroup

Creating and Deleting group

You can also create,add and remove groups and users by GUI .

Creating a User useradd bilal

Assigning a password to a User passwd bilal

************

Creating new user and assigning password , shell and id

useradd umar –p abc123 -s /sbin/zsh -u 574

Deleting a user add users home directory as well userdel –r bilal

‘-r’ /home/bilal

Creating and Removing User

ac who (will display who are currently logged in and what terminals they are using)

Monitoring activities of users

Managing Password security password should be not simple Password should be not so long Password should not be written near your pc Password should not be very difficult

su (will switch to root user, will ask for password before switching ) su bilal (will switch to the user bilal, will ask for bilal password before switching) su umar (will switch to the user umar, will ask for umar password before switching)

Switching users

sudo (The user must authenticate himself with the password , list of

authorized users is in /etc/sudoers and super user can only access)

First you need to add the user in the file sudoers and assign a password

sudo fdisk –l /dev/hda1 (After this the system will ask you for the password, and will match it in the /etc/sudoers/ file)

Granting Root powers to a user on occasion ‘5 minutes default time’

The above command is a system administrator level Command but a normal user will execute it ‘system Disk checking’.

Taking back Root powers from a user bash –r (First shift to that user account and type the command)

Login prompts. If the user is not root and tries to type wrong password of root

then the system will halt and a warning message is issued. A file /etc/shadow is examined to see if any restrictions are on this

particular user. Password prompts. User id and Group id being used are set on terminal. Terminal environment is set. The home, mail, shell, log is preserved. The default path of user are set, e.g mail, home etc… If there are any greeting messages then they are set. Lastly the user command shell starts.

Users Login Process

1. This can be set to both a user and a group .2. Quota management is not enabled by default and has to be enabled and configured manually.3. Through the vi editor change the file /etc/fstab and set the rules.

Disk Quotas

Gui control panel