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Linux Systems Administration

Most system administration functions on UNIX and Linux are performed as user "root". The root user is the superuser and is equivalent to the Windows "administrator" account. It is dangerous. You can delete the whole Linux OS without so much as an "are you sure?" prompt. The "root" account is all-powerful and not something to play with, unless you have your own system and do not mind reinstalling the OS daily. You are almost never logged in as root when using a system- the root login is strictly for configuration and administration of your system.

With that said, let's learn a few additional commands that can only be run as root. There will not be a lab for this lesson because you most likely do not have root access, unless you have your own system.

su Switch user. If you are logged in as a user, you can type in "su username" and you will be given a log in prompt for username. You will have to provide a password to actually log in. Typing "su" without a username is equivalent to "su root" and you will be prompted for the root password.
chown chown is a standard UNIX/Linux command that allows you to change the owner of a file/directory. To change the owner of a file/directory, become root by either logging in directly as the user root or use the su command as a normal user. Then you would type "chown newOwner filename" where newOwner is the username you want to change ownership to and filename is the name of the file or directory.
chgrp chgrp is a standard UNIX/Linux command that allows you to change the group of a file/directory. To change the owner of a file/directory, become root by either logging in directly as the user root or use the su command as a normal user. Then you would type "chgrp newGroup filename" where newGroup is the group-name you want to change group ownership to and filename is the name of the file or directory.
useradd This program adds a user to the system. For example, you can type useradd foobar to add the user foobar to the system. If you type useradd -m foobar, foobar will be added to the system and a home directory will be created. If you add a user to the system, you must add a password before they can use the account
passwd This command changes the password on an account. In order to change (or add) foobar's password, root would type passwd foobar . If a user runs the command, passwd, he or she will be prompted for a new passwd for their own account.
userdel This command is used to delete a user from the system. Only root can run this program by typing userdel username . If you want to delete the user's home directory at the same type, use an -r switch. userdel -r username

 

 

 

 

Please email me the answer to the following questions.

  1. What do you call the administrator account on a UNIX machine?
  2. What is the command to add a user to the system and create his home directory?
  3. If you are a UNIX administrator who is sick of working, what command might you run to delete the entire system?

 

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