Unit 4: Users, Groups and Permissions

This week I installed Webmin a web-based System Administration software for Unix I used a modified apt-get method to install Webmin. APT means Advanced Packaging tool. I had to add two lines to the apt file and a special validation key and then ran the update and install webmin commands using $ sudo aptitude update and $sudo aptitude install webmin Everything went smoothly with no problems.

There is much discussion about whether using aptitude or apt is the best method to install and upgrade software. See http://askubuntu.com/questions/1743/is-aptitude-still-considered-superior-to-apt-get/1749#1749 Bruce Fulton, our instructor, stated that aptitude has some advantages when it comes to removing packages but this may have to wait for another time. The  aptitude command works on my server setup and the installation went smoothly.

I then confirmed the IP address but forgot to use https instead of http the first time I tried to confirm the web address. Of course, I also had to confirm the security exception as I was using Firefox. After the security exception was confirmed, Webmin displayed the login screen so I knew I had completed this adventure.

Next, I examined the user and group settings in my Unity desktop environment and added a user (John Doe) using the Users application. I was not impressed with the limited set of options for the user configuration but this may be something I could use to add users temporarily or to add users with a very limited set of options.

The second installation was the installation of gnome systems tools on the Unity desktop environment. For this, I used $ sudo apt-get install gnome-system-tools in the Terminal application. Downloading the packages took some minutes and the installation was slower in my Unity desktop environment system than the webmin installation.

After the installation finished, I then added user (Jane Roe) using the Gnome Users and Groups utility. To my surprise, after I added this user  I did not see the name in my main user dialog box. Of course, I had not rebooted the desktop. Once I rebooted Jane Roe appeared in the Users and Groups dialog box.


Screenshot showing that Users Jane Roe and John Doe are missing

Screenshot showing that Users Jane Roe and John Doe are missing

I would not recommend adding users without understanding how users and groups are added using the command line in Linux. If you have a good understanding of the command for adding users and the file structure where the user’s details are found, then you can verify that you have added the user with the correct configurations.

The main Linux commands for adding and modifying users are useradd and ussermod See http://www.computerhope.com/unix/useradd.htm for a detailed explanation of the useradd command and its options. These commands have many options and it is important to understand the options before attempting to add users. I found studying the user options such as –d setting the user’s home directory and the user’s shell or –s option to be very helpful in understanding how Linux handles users. Understanding what I was doing before I did a hands-on assignment is good but especially with Linux commands as some errors could damage the system which I had taken some time to set up.

Finally, I examined the /etc/passwd file to verify that I had correctly added the new users. You can examine this file by using the $ less /etc/passwd command. You will need to scroll down in the file to get to the users and use q to quit the file. I used this technique both thin the desktop environment and my server environment to verify that I had added the users.

I still need to practice with the chmod command which can change read, write and execute commands on users’ files. It is easy to think of chmod as change mode which is essentially what is done when the file permissions are changed.  For a number of chmod options see http://www.computerhope.com/unix/uchmod.htm For more on Linux permissions see http://www.tuxfiles.org/linuxhelp/filepermissions.html I found this website to be very easy to understand http://www.linux.org/article/view/file-permissions-chmod The MakeUse of post explains how to add multiple permissions to files using the chmod command.

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