command line

By default, most instillation of Centos will end up having the default protocol set to be dynamic (DHCP) for obtaining the IP address. For a web server this is not what we want as it will be no good having the IP change and then having to change DHCP records to correctly point to the new IP address. This tutorial will show you how to change the IP protocol for a Centos 7 OS to use a static IP instead of a dynamic IP.

Start by navigating to the directory that contains the IP config files.

You should get a list of files that are inside this directory. Most of the time there will be a file named “ifcfg-eth0”, but its not always the case. The name may vary, but it will always begin with “ifcfg”. When you are looking at the results have a look and see what files are in this directory that begin with “ifcfg” and work from there.

Once you have found the correct file you will see that there is a variable near the top of the file called “BOOTPROTO”. This will be set to “dhcp” this needs to be changed to be static. You will then need to go to the bottom of the file and alter or add some values for the network information. Your file should look like the file below once you have finished. (be sure to replace the placeholder info with actual IP information).

If you are in a situation where you have no access to the machine other than command line, you will need to use VI to edit the file. Once you have a static IP you should be able to connect to the machine using SFTP and modify the file using a text editor.

Once you have made edits to the file, you will need to restart the networking on the server. The following command will restart the networking and should now allow you to access the server using the static IP that you have defined.

 

There are many different ways to get the IP of the current server on linux machines which causes a lot of conflict across the different variations. Not all operating systems use the same command and sometimes the command used is not built in as part of the operating system. If you are running the minimal install of Centos 7 you will find that the standard command “ifconfig” does not exist. You could install this if you wish, but there are methods to obtain this using the tools you have available already. There are 2 possible ways to get the IP address.

This will dump out quite a bit of info, the import part being the IP address of the server. This can be a bit messy, but is a more reliable method of obtaining the servers IP. If you want a quick an easy way of finding out what it is, you can run the following command to display just the IP. This is not as reliable and will sometimes return a blank value for a server that has not been configured correctly.

 

command line

Installing can be quite simple to do and also very dangerous as you install something, it completely wrecks apache and now your web server wont start back up again. Well worry not, its very easy to uninstall anything that you have installed. The first thing you need to know is that the name of the package changes from the name of the original file that you downloaded and installed. You will first need to perform a search of everything that is installed to get the name of the package you are looking for. Using grep will make this way easier.

This will generate a massive list of all of the packages installed on your system if you run it without the grep. Once you have found the name of the package you want to install run the following command to uninstall an RPM package from your system.

If the RPM that you installed was part of another application such as an apache module, make sure to run the command to restart the application in case it has crashed with the install of the RPM.

Thankfully this is very easy to perform. You can begin to get over the mini heart attack you had when your server went down now 🙂