Chapter 4
Installing a Red Hat Server

Red Hat Enterprise Linux (RHEL) is the most popular Linux distribution, and chances are that you'll install it many times during your Linux career. Gaining experience with this distro's installation process will help you become a Linux expert. If you read through Chapter 2, “Installing an Ubuntu Server,” some items within the installation steps will feel familiar. However, there are enough differences between installing the two Linux distributions that you can get tripped up.

Therefore, our goal in this chapter is to assist you through your first installation of a RHEL distribution. We'll provide step‐by‐step guidance, help you avoid pitfalls, and ultimately build your sysadmin skillset.

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IN THIS CHAPTER, YOU WILL LEARN TO

• Review needed Red Hat Server hardware resources
• Determine the requirements for a virtual Red Hat system
• Obtain Red Hat Server software
• Conduct an installation of a Red Hat Server
• Audit the Red Hat Server's installation

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Pre‐Installation Requirements

Before taking a look at the needed resources, we need to have a chat about fees associated with RHEL. This particular distribution requires you to pay money to use it. For example, every year it would cost you about $350 to potentially more than $1,300 per system to run RHEL on a server. This is expensive if you just want a Linux distribution to work with for learning purposes! But don't give up hope, because we've got a free solution for you. The CentOS Linux distribution is free of charge and is a community‐supported version of RHEL. For learning purposes, it will work perfectly for you!

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UNDERSTANDING RED HAT CHARGES FOR RHEL

While it may seem odd to you that a company charges for its Linux distribution, Red Hat has solid reasoning and experience behind what it calls its subscription model. When you pay a subscription, besides getting the RHEL distro to run on a server and access to any of its software updates, you have access to experts.

As an example, suppose you have a mission‐critical system running RHEL. The system starts to exhibit some performance issues. Your subscription with Red Hat includes a system performance expert, who will analyze and evaluate your server configuration and then make recommendations for improvement. In addition, you can talk to RHEL security experts and get technical support at any time.

Red Hat has been using this subscription model for more than 20 years, and the popularity of this Linux distribution shows that the model works. You can find more information about the Red Hat subscription model at redhat.com.

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For our purposes in this book, the CentOS distribution without a GUI will provide what is needed since our target is a headless server (see Chapter 2 for a more detailed explanation as to why a GUI is typically not used in modern server rooms). Specifically, we're using a CentOS 8 Linux distribution.

Before starting your CentOS installation, it's a good idea to review what resources are needed. This step is important in order to achieve a successful Linux distribution installation.

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UNDERSTANDING BASIC VIRTUALIZATION TERMS

If you're unfamiliar with virtualization computer terms, it's a good idea to read through the first several pages of Chapter 22, “Exploring the Virtualization Environment.” If you'd like a quick jump start instead, a few basic definitions were covered in Chapter 2.

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You may perform the CentOS installation on a physical system, or you may install it as a virtual machine on a host system. Thus, in the next few sections, we'll look at the hardware requirements needed for installing the CentOS distribution directly on a physical server and for installing it within a virtualized environment.

Hardware Requirements

If you plan on installing the CentOS 8 distribution directly on a headless server, your computer must support a 64‐bit processor architecture. Here is a list of a few that will work well:

• AMD amd64
• ARM64 (not supported by RHEL)
• Intel amd64
• POWER9 (not supported by RHEL)

Besides having the proper processor on your system, you need to have enough resources available to avoid a sluggish system. Table 4.1 shows the recommended resources to support a well‐running CentOS distro.

TABLE 4.1: Recommended Server Resources for CentOS Distribution

RESOURCE	MINIMUM	RECOMMENDED
CPU	1.8 GHz	2 or more GHz
Memory	2 GB	2 GB per logical CPU
Disk space	10 GB	20 or more GB

Notice the “per logical CPU” tag in the recommended memory. This is because CentOS can support some rather powerful CPUs, and it treats every core (or thread) in a multicore (or thread) processor as a logical CPU. So if you have a dual‐core processor, it is recommended that you have 4 GB of RAM on your system, while a quad‐core processor needs 8 GB of memory.

Also, keep in mind that these recommendations are only for the operating system. Increase these resources to meet the needs of the application(s) you will run on the server.

If you don't have access to a physical server, you can set up a virtual environment on a laptop or an old desktop. Using a virtualized system on your laptop provides a great deal of flexibility. Wherever you go with your laptop, you can learn about Linux.

Virtual Server Requirements

If you plan on running the CentOS distribution as a virtual machine (VM), you need to ensure that the host machine's operating system is supported by the hypervisor.

For this book, we're focusing on the Oracle VirtualBox hypervisor software. Here are a few of the operating systems on which it can run:

• Windows 8.1
• Windows 10
• macOS High Sierra
• Ubuntu 18.04LTS

This list is always evolving. Thus, it's a good idea to visit the Oracle VirtualBox manual website, virtualbox.org/manual, and view the currently supported host operating systems.

Running a virtualized environment will increase the needed resources on your system. You'll need to make sure that the host machine can handle not only the hypervisor, but the CentOS VM as well. Table 4.2 lists the recommended host machine resources for a virtualized CentOS server.

TABLE 4.2: Recommended Host Machine Resources for a CentOS VM

RESOURCE	MINIMUM	RECOMMENDED
CPU	2 GHz dual core	2 or more GHz dual core
Memory	4 GB	16 or more GB
Free disk space	25 GB	30 or more GB

These resource recommendations are guidelines, not rules. Thus, you may need slightly more resources or get by with a fewer. Also, these recommendations assume you are running only one VM at a time. You'll need more resources on your system if you plan on running multiple VMs at the same time or running a VM along with several other apps.

After you have the right level of resources on your host system, you're ready to start downloading the needed software. We'll cover this in the next section.

Finding the Software

After you determine that you have the appropriate resources, but before you start the installation process, you need to have the proper software. You'll want to make sure that you get the correct version and type. For the larger software files, it's also critical to verify that no corruption has occurred when the software was downloaded. If you have a corrupt software file, you'll end up needlessly wasting your time or, worse, delaying the completion of an important installation project.

Oracle VirtualBox

We recommend that you use Oracle VirtualBox as the hypervisor on your system. If you did not download this software when you read Chapter 2, you can now download the latest version of this software from virtualbox.org.

It is important that you get the correct platform package of VirtualBox. You'll see a list of potential host systems on the VirtualBox website, such as the following:

• Windows
• macOS
• Linux

Make sure to select the VirtualBox package for the system on which the CentOS virtual machine will be running. Often, people make an incorrect choice because they confuse the host system with the virtual machine. Here's an example that may help: if you have a laptop running Windows where you plan on installing CentOS as a VM, then Windows is the host, and you'll want to download the VirtualBox package for Windows. Our examples in this chapter are based on a Windows 10 host system.

CentOS

To install CentOS as a VM, besides the hypervisor software (and the correct amount of resources on the host machine), you need a CentOS ISO image file.

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Real World Scenario

Understanding an ISO Image File

An ISO image file (also called an ISO image) is a specially formatted package file that contains all of the files needed to boot a system. The ISO image file is used to boot and then install the distribution.

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To find the needed CentOS ISO image file, first go to the website: centos.org/download/. The type of processor you have will determine your next step. Click the appropriate CPU type for your processor under the CentOS Linux section, shown in Figure 4.1.

FIGURE 4.1 Option to choose to access the appropriate CentOS ISO image file download site

A new browser window will appear, allowing you to select from several sites to start the download process. You can click any of the sites. Once you do, you should get a window similar to what is shown in Figure 4.2.

Click the CentOS‐8 * boot.iso link to start the download of the CentOS ISO image file. Depending on the web browser you are using, you may have to deal with some pop‐up windows that want to confirm it is OK to download this file. You'll most likely want to keep this website open or bookmark it in your browser, because we use the checksum information provided here soon.

FIGURE 4.2 Option to choose for CentOS ISO image file download

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ENDURING A POTENTIALLY PAINFUL DOWNLOAD OF AN ISO FILE

ISO image files are sometimes large and can hover around 2 GB to7 GB in size. Fortunately for us, the CentOS boot ISO image file isn't that big. However, if you have a slow Internet connection and desire to get a large ISO image file, it could take hours to download! In these cases, it's worth your time to go visit that friend who has fiber‐based Internet and is willing to share their bandwidth.

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It's important to verify that no corruption occurred while the ISO file was downloading. To do this, we'll use hashing.

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UNDERSTANDING HASHING

Hashing uses a one‐way mathematical algorithm to create a fixed‐length hash, which is basically a series of letters and numbers. A hash is also called a message digest, a hash value, a fingerprint, a signature, or cipher text. One cool thing about hash values is that certain hashing algorithms produce the same hash value for files that are the same. Thus, you can take a file with a picture in it and copy it to another location across the network. If we use hashing to produce a hash value for the original picture file and for the copied picture file and those two hash values match, we know that the picture was not corrupted when it was copied to the new location.

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While you work your way through the following exercise, you may find you have a corrupted CentOS ISO image file. If this is the case, you'll need to re‐download the file and check it via hashing again.

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Real World Scenario

CHECKING THE CentOS ISO IMAGE FILE

Once the CentOS ISO image file is completely downloaded, you need to verify it. Follow these steps to verify the ISO image file:

1. On your Windows 10 system, open the Windows 10 PowerShell app by typing Windows PowerShell in the search bar and clicking the resulting Windows PowerShell app icon.

   

2. After the Windows PowerShell app window is open and you have a prompt, assuming you downloaded your CentOS image file to the Downloads folder, type cd Downloads and press Enter. The prompt should now show that you are in the Downloads folder.
3. Run the PowerShell hashing utility on the CentOS image file by typing Get‐FileHash CentOS and press the Tab key so that PowerShell autocompletes the CentOS's image filename for you. Go to the next step before you press Enter.
4. You can complete the rest of the PowerShell command by pressing the spacebar, typing ‐Algorithm SHA256 (this option is not required), and pressing Enter. Be patient! It may take a while for the command to output the SHA256 hash value. You should see something similar to the following:

   

    

   Don't exit the PowerShell window yet. You need to compare your resulting hash value with the current SHA256 hash value on the website from which you downloaded the CentOS ISO image file.

5. Go back to your web browser and look at the website page from which you downloaded the CentOS ISO image file, and click the CHECKSUM (or something similar) link to open the page containing the CentOS‐8 * boot.iso image file's SHA256 hash value.
6. Compare the hash value on the website with your hash value in PowerShell for the CentOS‐8 * boot.iso image file. (Be aware that case does not matter. A lowercase b is considered a match for an uppercase B.) If the values match, no file corruption occurred when you downloaded the file. However, if the hash values don't match, you'll need to download the file again and repeat this checking process.
7. Type exit at the PowerShell prompt to leave the app.

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Verifying that the CentOS ISO image file is a good copy will save you time. If you tried to use a corrupt image file in an installation, it may work partway through the process and then quit before completion. That's frustrating. It's always best to check that your ISO image file is good before proceeding within an install.

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PREPARING FOR A HARDWARE INSTALLATION

If you are planning on installing the CentOS distribution directly on a computer's hardware instead of creating a VM, you need to do one additional step after checking the ISO image file: create a bootable media device. While bootable DVDs were popular many years ago, most hardware installations are handled through a bootable USB drive. The process of creating this bootable USB (or DVD) is called burning an ISO file to a USB drive. You cannot just copy the file to the USB. Instead, you'll need a special software app that will burn the ISO properly. To find the right software, open your web browser and go to your favorite search engine. Type burn a bootable USB and press Enter. The resulting list will have several sites that point to free software with instructions. Once you have your CentOS ISO image file properly burned to a USB (or DVD) drive, you'll be able to boot your system and perform the installation process similar to what is covered in the next section.

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Now that you've verified your copy of the CentOS ISO image file and have downloaded the Oracle VirtualBox hypervisor software, you're ready to start the installation. We'll cover that process next.

Running the Installation

To create a CentOS VM, you'll need to first install the hypervisor, Oracle VirtualBox. Once that software is up and running, you can set up and install CentOS as a VM using its ISO image file and the hypervisor.

Oracle VirtualBox

The Oracle VirtualBox hypervisor software will allow you to do much more than set up CentOS as a Linux VM. You can also install another version of Windows within a VM and use it to try features or configurations you normally wouldn't do on your main system.

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CONSIDERING THE INSTALLATION OF ORACLE VIRTUALBOX

If you read through Chapter 2 and completed the exercises, you already have Oracle VirtualBox installed on your host system, so you can skip ahead to the next section in this chapter. However, if you did not read through Chapter 2 or did not complete its exercises, go back to the “Installing Oracle VirtualBox on Windows 10” exercise in Chapter 2 and complete it. This exercise will take you step‐by‐step through the Oracle VirtualBox installation process. When you have finished that exercise, come back to this chapter for the next section.

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If you need to take a break, close out the VirtualBox interface window by clicking the X in the upper‐right corner. However, if you want to plow ahead, keep it open. We'll launch into installing CentOS in the next section.

CentOS

Installing the CentOS as a VM may feel overwhelming the first time you do it, and there are a few tricky items to negotiate along the way. We'll help you through this initial instance to build your confidence and help you avoid potential pitfalls.

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Real World Scenario

SETTING UP A CentOS CONFIGURATION WITHIN ORACLE VirtualBox

Prior to installing CentOS as a VM within the VirtualBox hypervisors, you need to perform a few basic tasks to create and configure a place for the new VM within the VirtualBox app. After you have completed these tasks, on your host machine you will have a folder for the new VM as well as two files within the folder—one file for the VM configuration information and one file acting as a hard disk for the VM.

Follow these steps to configure the CentOS VM. There are only a few steps needed to complete this part of the installation project, but they are important! So, don't skim through this exercise.

1. Open the Oracle VirtualBox app on your host system. How this is accomplished depends on the configuration you chose when installing the VirtualBox software. You may have to find it via the menu search feature on Windows 10 or simply click the VirtualBox icon on the desktop or taskbar. Once you have the app open, you should see a window showing the Oracle VirtualBox Manager that looks similar to this (note that you may or may not have an Ubuntu Server VM showing in your Manager window):

   

2. In the VirtualBox Manager window, using the top menu within the window, select Machine ➢ New. This will start the process of configuring the CentOS VM and produce the following Create Virtual Machine window:

   

3. Enter the name CentOS Server in the Create Virtual Machine window's Name box.
4. Click the Next button to reach the Memory Size window, which looks similar to the following:

   

    
5. By either typing in the memory setting box or using the up‐arrow button, change the CentOS Server memory to 2048 MB.
6. Click the Next button in the Memory Size window to reach the Hard Disk window.

   

    
7. Double‐check that the Create A Virtual Hard Disk Now option is selected. (You can tell that a particular option is selected by the circle next to it being filled with a dark color, as shown in the previous figure.) If you need to select Create A Virtual Hard Disk Now, click the empty circle next to the option.
8. Click the Create button in the Hard Disk window, which will open another configuration window called Hard Disk File Type.

   

    
9. Within the Hard Disk File Type window, ensure that the VirtualBox Disk Image (VDI) is selected.
10. Click the Next button, and the Storage On Physical Hard Disk window will appear. This configuration window looks similar to the following:

    

     
11. Double‐check that the Dynamically Allocated setting is chosen.
12. Click the Next button to open the File Location And Size window. In this window, you will see where the VM's virtual disk file is created as well as its size. This configuration window looks similar to the following:

    

     
13. Change the file size to 20 GB by typing 20 within the size box.
14. You are now ready to create the basic configuration and virtual disk file of the VM. Do so by clicking the Create button.

    You should now be back at the VirtualBox Manager window with the CentOS Server VM in the left pane, as shown here:

    

    We have a few more configuration steps to take before the VM is completely configured.

15. Click the Settings button in the VirtualBox Manager's top‐right pane, which opens the Settings window for the CentOS Server VM.

    

16. In the Settings window, click Network in the left pane to open the Network Settings window for the CentOS Server.

    

    The next few steps help you to set up a second network interface card (NIC) on the CentOS Server. This allows your VM to act as an independent node on your network.

17. In the Network Settings window's right pane, click the Adapter 2 tab.
18. In the Adapter 2 tab window, click the empty box next to Enable Network Adapter.
19. Still in the Network Settings’ Adapter 2 tab window, use the arrow to open the drop‐down menu in the Attached To box, and select Bridged Adapter. Except for the Name box, your selections should look similar to the following:

    

20. Click System in the left pane to open the System Settings window for the CentOS Server.

    

21. In the Pointing Device selection, click the down arrow and select USB Tablet from the drop‐down menu. This is a critical step that will avoid problems with your mouse working inside and outside of the virtual machine.
22. Click the OK button to save the changes you made to the CentOS VM settings.

    You should now be back to the VirtualBox Manager window. Pat yourself on the back! You have successfully configured the CentOS Server VM.

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Your hard work is about to pay off. You are now ready to install the CentOS distribution on the virtual machine you just configured within VirtualBox.

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Real World Scenario

INSTALLING CentOS AS A VM

After configuring the CentOS VM within the VirtualBox hypervisor, you can perform the actual installation of the Linux OS. Conducting the installation process on a VM is similar to conducting it on a physical server. There are just a few differences, such as loading the ISO image file into the virtualized DVD drive.

Follow these steps to install CentOS as a VM:

1. If not already opened, open the Oracle VirtualBox hypervisor app on your host system.
2. If you have multiple VMs configured in your hypervisor, click one time on the CentOS Server VM to select it.
3. Click the Settings button in the VirtualBox Manager's top‐right pane, which opens the Settings window for the CentOS Server VM.
4. In the Settings window, click Storage in the left pane to open the Storage Settings window for the CentOS Server. It will look similar to the following:

   

5. In the Storage Settings window's middle pane under Controller: IDE, click the word Empty to open the Attributes pane for the IDE optical drive.

   

6. In the Storage Settings window's Attributes pane, click the DVD image to produce a drop‐down menu, and select Choose/Create A Virtual Optical Disk. An Optical Disk Selector window will appear that looks similar to the following:

   

    
7. In the Optical Disk Selector window, click the Add icon, which will open the Windows Explorer utility, and you will see “Please choose an optical disk file” in the window's title bar.
8. Navigate to the location of your CentOS ISO image file, select the file by clicking it, and then click Open. The Optical Disk Selector window now looks similar to the following:

   

    
9. In the Optical Disk Selector window, click Choose, and you're returned to the Storage Settings window's Attributes pane with the CentOS ISO image filename displayed under Controller: IDE.
10. Click OK to keep the virtually loaded ISO image file and return to the main VirtualBox Manager window.
11. Boot your CentOS Server VM by clicking the Start button in the VirtualBox Manager's top‐right pane.

    You may see lots of messages go by on your screen. Let the process continue until you reach this window:

    

12. Press Enter to start the installation process.

    You may see several more messages go by on your screen. Let the process continue until you reach this window:

    

13. Using your arrow keys, select the language you prefer and press Enter. The next window, Installation Summary, will look similar to the following:

    

14. Click Network & Host Name to reach a screen that looks similar to this:

    

15. Within the Network & Host Name window, click the second Ethernet listed to select it. Now click Off in the screen's upper‐right corner to turn this network on. It should now look similar to this:

    

16. Still within the Network & Host Name window, click Done to save your settings and return to the Installation Summary screen.
17. Within the Installation Summary screen, click Installation Destination to reach a window that looks similar to this one:

    

18. Click Done in the Installation Destination window's upper‐left corner to accept the defaults and return to the Installation Summary screen.
19. Within the Installation Summary screen, click Software Selection to reach a window that looks similar to this one:

    

20. In the Base Environment pane, click the circle next to Server to select it. This selection chooses a CentOS server without any GUI elements, as is desired here.
21. Click Done in the Software Selection window to return to the Installation Summary screen.
22. At this point, the Begin Installation button in the Installation Summary window's lower‐right corner should no longer be grayed out. Click Begin Installation. The installation will start, and a Configuration window will appear that is similar to the following:

    

23. Click Root Password to reach a screen that looks similar to this:

    

24. In the Root Password field, type in a password for the root account. Be sure to choose one that you will remember!
25. Tab to the Confirm field, and type in the same password you entered in the previous step. If the passwords don't match, you will not be able to proceed past the next step, so type carefully!
26. Click Done in the upper‐left corner of the window to return to the Configuration window.
27. Click User Creation to reach a screen that looks similar to the following:

    

28. Within the Create User screen, type your first and last name in the Full Name field.
29. Tab to the User Name field, and type sysadmin.
30. Tab to the Password field, and type in a password. Be sure to choose one that you will remember!
31. Tab to the Confirm Password field, and type in the same password you entered in the previous step. If the passwords don't match, you will not be able to proceed past the next step, so type carefully!
32. Click Done in the upper‐left corner of the window to return to the Configuration window.
33. In the Configuration window, you may have to wait a while for the software to finish downloading and installing. When this part of the process is completed, you'll see a screen containing a “Complete!” message like this:

    

34. Because the CentOS ISO image file has not yet been removed from the virtual DVD drive, click the X in the VM's upper‐right corner. You'll receive the Close Virtual Machine screen, which looks similar to the following:

    

35. Click the circle next to Power Off The Machine.
36. Click OK to power off the CentOS Server virtual machine.
37. Click the Settings button in the VirtualBox Manager's top‐right pane, which opens the Settings window for the CentOS Server VM.
38. In the Settings window, click Storage in the left pane to open the Storage Settings window for the CentOS Server.
39. In the Storage Settings window's Attributes pane, click the DVD image to produce a drop‐down menu, and select Remove Disk From Virtual Drive in the Storage Devices pane. The Controller: IDE item should show Empty, similar to the following:

    

40. Click OK to return to the VirtualBox Manager window.
41. Boot your CentOS Server VM by clicking the Start button in the VirtualBox Manager's top‐right pane.

    You may see messages on your screen. Let the process continue until you reach this window:

    

42. In the localhost login field (which is for the username), type root and press Enter. The password field will then display.
43. In the password field, be aware that nothing will show as you type in your password. There are no symbols such as asterisks or dots shown. Type in the password you created for the root account earlier, and press Enter.
44. After you log into the system successfully, you'll receive a prompt similar to this:

    [root@localhost:~]#

    This prompt is where you enter your commands, and it's called the command‐line interface.

    The next several commands assume that your host machine is connected to a network.

45. Updating software on a newly installed Linux system is an important step, and before you begin this process, you can see whether there are any updates to perform. To do this, type dnf list upgrades and then press Enter. (Note that if no updates are listed, you can skip the next two steps.)
46. Once you receive the prompt, update the software by typing dnf upgrade and pressing Enter.
47. Whenever the software update process asks “Is this ok [y/N],” type y and press Enter.

    This software update may take a while, so go get a cup of coffee and check the latest statuses on social media.

48. When you receive the “Complete!” message and a command‐line prompt, the installation process is complete. Type poweroff at the prompt and press Enter to shut down the system.

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Congratulations! You've installed CentOS as a VM within the VirtualBox hypervisor, and you can use this Red Hat distribution twin to learn more about RHEL. Now that the installation process is complete, it's a good idea to check and make sure everything is OK. We'll cover that next.

Checking the Installation

Though the system may appear fine after an initial installation, it's wise to perform a few checks. While it's a little difficult to understand everything you are looking at in this section, reviewing this information will help you as we cover these utilities and concepts in detail later in the book. Also, you can return to this section for guidance the next time you perform a CentOS distribution installation.

First, boot your CentOS Server VM. After the system has booted, log into the terminal using the root account name and password, and do the following:

• Check for boot errors. There are three commands that can help you check for boot errors. The first is dmesg, and to view this information, you don't need super user privileges. This will display the kernel ring buffer, but that data is useful only if you check it soon after the system has booted.

  To see boot messages long after a system boot, type less /var/log/boot.log at the prompt and press Enter. You can move forward through this log by pressing the spacebar. When you are done looking at the information, press the Q key to exit to the command‐line prompt.

  You can look for boot errors and all kinds of messages via the journalctl command. To peruse this information, you will also need the spacebar to move forward and the Q key to quit your viewing.

• Determine the default boot level. The default boot level on a Linux system determines what applications are started when the system boots. The command to see this information is systemctl get‐default. It does not require super user privileges to use.

  Most likely, you will see multi‐user.target when you issue this command, meaning that even if GUI software is available, the GUI will not start on boot. You'll learn more about targets later in this book.

• Check version information. Determining the version numbers of the system's main components is helpful when tracking down problems. First, make sure you have the right CentOS distribution version installed by typing cat /etc/redhat‐release at the prompt. The distribution name and version is displayed.

  Check the Linux kernel version too. This is important to know because different features (and bugs!) exist in the various kernel versions. To see this information, you'll need to type uname ‐r at the command‐line prompt. You can also view this information via the cat /proc/version command.

  Finally, look at the version of the Bash Shell running on the system. This is easy to accomplish by using the bash ‐‐version command.

Once you've completed your checks, celebrate! You worked hard to get this CentOS distribution installed correctly.

The Bottom Line

• Review needed CentOS hardware resources. Determining the hardware resources required for a CentOS installation on a physical or virtualized server helps to ensure a successful completion of the install. It also avoids important project delays due to under‐resourced systems.
  • Master It Imagine that you need to install the CentOS distribution on a physical server that has a dual‐core 2 GHz CPU, 200 GB hard drive, and 2 GB of RAM. Are the server's resources at the recommended level? Why or why not?
• Determine the requirements for a virtual CentOS system. Installing the CentOS distribution as a VM on a host system has different requirements than a direct installation on a physical server. It is critical to evaluate the host system so that the installation is successful.
  • Master It Your project team is planning on installing two CentOS VMs on a host system that has a quad‐core 2.8 GHz CPU, 200 GB of free disk space, and 32 GB of RAM. Are the host system resources sufficient? Why or why not?
• Obtain CentOS software. To install the CentOS Linux distribution, you must have the proper ISO image file. This is true whether you are installing it directly on hardware or as a VM. Besides getting the ISO file, you need to ensure that it is not corrupted so that the installation proceeds well.
  • Master It You've downloaded the CentOS ISO image file, but you are concerned that during the download process, file corruption occurred. What should you do to see whether the ISO image file is corrupt?
• Conduct an installation of a CentOS distribution. There are several steps to successfully install a CentOS distribution, and it is critical to make sure you complete all of them. Skipping a step can cause problems immediately as well as problems later, if you can even get the system to boot.
  • Master It Your sysadmin team has correctly installed the CentOS software from the ISO image file, and the system booted without any problems. What's the next step?
• Audit the CentOS distribution's installation. If you had some problems while booting the system, there are a few commands you can use to look at helpful boot messages. But even a successful installation still requires a few additional checks.
  • Master It At your company, you have completed the entire CentOS distro installation process on a new system without any problems, but you then ran into issues the last time the server was rebooted. You need to review the boot messages to track down the problem(s). What log file can you use to view these messages?