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LFCS - Installing CentOS 7

Discussion in 'LF Linux Articles' started by Jarret, Nov 16, 2016.

  1. Jarret

    Jarret Moderator Staff Member

    Linux Distribution used for the LFCS Certification is CentOS. You have your choice of three Distribution types and CentOS is one of the three. Know that CentOS is Red Hat based and the items specific to CentOS and other items not specific to a distro can help you on the Red Hat Certified Systems Administrator (RHCSA) exam.

    Media

    To get CentOS installed, you first need to download the file needed to install the Operating System (OS). The files can be found at www.centos.org. More specifically, you can go directly to https://wiki.centos.org/Download to get the necessary file you require. The files are based off of the processor type your system uses and which type of install you will perform.

    NOTE: For the purposes of the certification to install the MATE Desktop, you need to use the 64-bit version.

    At the top of the page, you can see that for i386, there are six choices. You only need to worry about three of them: DVD, Minimal and Everything. If you scroll down to the heading of “AltArch Releases”, there is a download here for the file to perform a NetInstall. These four are the main types you need to know about.

    The DVD install, about 4 GB, is an ISO file which can be burned to a DVD, or used from a USB thumb drive to install CentOS 7.

    The Minimal install is an ISO file which is smaller and contains less extra software which is installed by default. The file is 608 MB and can be burned to a CD, DVD or even a USB thumb drive. The image loads the basic OS to run and function without any extras.

    The Everything image is 7.2 GB to be burned to a dual layer DVD or thumb drive. The file contains everything on the DVD ISO file that you can do by installing extras not on the DVD image.

    The NetInstall allows the OS to be loaded from the network (Internet) as well as being used as a rescue disk. The image is 318 MB and can easily fit on a CD or run from a USB thumb drive.

    Select your appropriate image, download it and burn the image to the media you desire (DVD, CD or thumb drive).

    NOTE: The image can be burned to a thumb drive by using Unetbootin. Also be sure to get the proper image for your processor. Many sites say there are no images for a 32-bit system (i386), but they are there.

    Hardware

    The requirements for CentOS 7 are as follows:

    • CPU (at least dual core or one core with hyper-threading – two or more threads total)
    • 1 GB of RAM per each CPU
    • 10 GB of Hard Drive Space
    • DVD or USB for booting the ISO image
    • Network connection (for NetInstall)
    Of course, it is best to have more than the minimum requirements, but the minimum usually works fine unless you are going to add a lot of different services.

    Software Installation

    As discussed before, there are four type of installation media. All types are approximately the same, but the NetInstall has one extra step which the others do not have. The NetInstall requires a URL to access the media on a network or the Internet. With the installations being the same, except for the one step, they can all be covered at once.

    Place your media in the system on which CentOS 7 will be installed and start up the system to boot from your media.

    Once booted, you should see a screen similar to Figure 01. The second option “Test this media & install CentOS Linux 7” should be highlighted. Use the up arrow key to move the highlight to “Install CentOS Linux 7” and press ENTER.

    Figure 01.jpg
    FIGURE 01

    After some more loading and executing, you should see Figure 02. Here, you choose the language used for installation. Make your choice and then press the “Continue” button in the lower right corner of the screen.

    Figure 02.jpg
    FIGURE 02

    Figure 03 should appear and give you all of your choices for the install and the main OS setup. Set the Date and Time. The Language Support should reflect the same Language you chose previously in Figure 02. The Keyboard should also reflect the default setting for the Language selected. The Security Policy defaults to none. The Installation Source is set to the inserted media (unless you used the NetInstall). The Software Selection will show all available selections (if you used a Minimal install, then only Minimal will appear here). The Installation Destination needs to be set by you because it does not default to a media, but waits for you to select it. By scrolling down, you can see an option for Network and Host Name. With any install, especially the NetInstall, the network can be enabled.

    NOTE: Any setting can be changed from the defaults which were set by the system when you first got to this screen.

    Figure 03.jpg
    FIGURE 03

    By opening the Network and Host Name option, you will see options similar to Figure 04. Select your network card on the left side of the screen and enable it on the right side. By default, all Network Interface Cards (NIC) are disabled. At the bottom of the screen you can specify a Host Name. By selecting the NIC you wish to use, you can also select the Configure button to edit the settings as you need. Once done, click the Done button on the top left of the screen.

    NOTE: The network card MUST be enabled and have access to the remote media for a NetInstall.

    Figure 04.jpg
    FIGURE 04

    If you need access to remote media, such as a NetInstall, you need to then go to Change Installation Source as shown in Figure 05. Even if you do not use the NetInstall image, you can still access remote media. Remote media can allow a Minimal install image to perform a full DVD install. The necessary settings are for the “On the Network” option. The main two you would need are as follows:
    NOTE: Do NOT click the “This URL refers to a mirror list” check box.

    Figure 05.jpg
    FIGURE 05

    Set up a Proxy if needed. If the files are on a local network Web server or FTP Server, then enter the path to the server and files.

    The Software Selection is shown in Figure 06. The screen shot shows the selections you can make, but only a Minimal Install will be shown if you have used the Minimal Install media. Select your preferred choice, but the Minimal Install should work fine to use for the rest of the articles. Select the Done button when you have made your choice.

    Figure 06.jpg
    FIGURE 06

    The Installation Destination is a very important option. The screen is shown in Figure 07. Select the hard disk you wish to install CentOS onto and then make the appropriate selections in the lower portion of the screen. The system can configure the partitions as it wants or you can override the settings. You can also encrypt the data on the hard disk. The option to “I would like to make additional space available” will allow you to modify the automatic partitioning if you choose. Click Done when finished with your settings.

    Figure 07.jpg
    FIGURE 07

    Once back at the main screen, select “Begin Installation” when you have configured all the options. The button will be dimmed until all settings are configured which are required to perform the install.

    Figure 08 should appear. The Root password for the OS needs to be set as well as setting up a user. First, set up the Root password. If the password is “weak”, then you need to click the Done button twice.

    Figure 08.jpg
    FIGURE 08

    To set up a user account, which is wise, you will see Figure 09. Specify the full name of the user. The system will fill in a default user name, but this can be changed. Check the box to make the user an administrator. Specify the password and retype it. If the password is weak, you will have to click on the Done button twice.

    Figure 09.jpg
    FIGURE 09

    Once the installation is completed, Figure 10 should appear to signify everything is done and you can reboot. When specified, remove the installation media to allow the system to boot into CentOS 7.

    Figure 10.jpg
    FIGURE 10

    CentOS has no Graphical User Interface, but we will remedy that in a future article.

    Troubleshooting

    If your CentOS system should become unusable and you need to get access to the files, then boot from one of the media choices. At the main menu, select “Troubleshooting” as shown previously in Figure 01. A new menu should appear, Figure 11, which gives you the option to “Rescue a CentOS Linux system”. You will now have choices to access your Linux system and make changes to the system files or copy the files.

    NOTE: You can also run a memory test from the Troubleshooting Menu to test the Random Access Memory (RAM).

    I hope this gets you started to learning about CentOS and maybe even the LFCS certification. The CentOS portion of the LFCS is close to the Red Hat Certified Systems Administrator (RHCSA) certification. Practice the various media types to be proficient in CentOS installation.
     

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