There are three types of users in linux  System users: ?  Super user: ?  Normal 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: ?

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: ?

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

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

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

Users and Groups

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. Giving file permissions to files and directories Command -option argument description

Group Information File The files which keeps the information of group  The group file : (etc/group) group name Password Group id  Assigning password to more then one user chpasswd username:password chpasswd umar:abc123 usman:ord4446 zahid:sleep :....

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 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

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

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

 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.

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. Gui control panel