Booting the Installation on 64-bit AMD, Intel, and ARM systems

Table of Contents

Starting the Installation Program
- Booting from Physical Media
- Booting from the Network Using PXE
The Boot Menu

You can install CentOS from the ISO images stored on hard disk, or from a network using NFS, FTP, HTTP, or HTTPS methods. Booting and installing from the full installation DVD is the easiest method to get started with. Other methods require some additional setup but provide different advantages that might suit your needs better. For example, when installing CentOS on a large number of computers at the same time, the best approach is booting from a PXE server and installing from a source in a shared network location.

The following table summarizes the different boot methods and recommended installation methods to use with each:

Table 1. Boot Methods and Installation Sources
Boot method	Installation source
Full installation media (DVD or USB)	The boot media itself
Minimal boot media (CD or USB)	Full installation DVD ISO image or the installation tree extracted from this image, placed in a network location or on a hard drive
Network boot (PXE)	Full installation DVD ISO image or the installation tree extracted from this image, placed in a network location

To create a boot CD-ROM or to prepare your USB flash drive for booting or installation, see Making Installation USB Media.

This chapter covers the following topics:

Booting from Physical Media (x86) describes how to boot the installation program using physical media (CentOS DVD, Boot CD-ROM, USB flash drive).
Booting from the Network Using PXE (x86) describes how to boot the installation program using PXE.
The Boot Menu (x86) contains information on the boot menu.

Starting the Installation Program

To start, first make sure that you have all necessary resources for the installation. If you have already read through Planning for Installation on 64-bit AMD, Intel, and ARM Systems, and followed the instructions, you should be ready to start the installation process. When you have verified that you are ready to begin, boot the installation program using the CentOS DVD or any boot media that you have created.

Excessive input (for example, clicking the mouse repeatedly) during the boot sequence can cause the installer to ignore keyboard input later in the installation process.

Occasionally, some hardware components require a driver update during the installation. A driver update adds support for hardware that is not otherwise supported by the installation program. See Updating Drivers During Installation on AMD64 and Intel 64 Systems for more information.

Booting from Physical Media

To start the installation program from a CentOS DVD or from minimal boot media, follow this procedure:

Booting the Installation from Physical Media

Disconnect any drives which you do not need for the installation. See USB Disks (x86) for more information.
Power on your computer system.
Insert the media in your computer.
Power off your computer with the boot media still inside.
Power on your computer system. Note that you might need to press a specific key or combination of keys to boot from the media or configure your system’s Basic Input/Output System (BIOS) to boot from the media. For more information, see the documentation that came with your system.

After a short delay, the boot screen appears, which contains information on a variety of boot options. Installation program automatically begins if you take no action within the first minute. For a description of the options available on this screen, see The Boot Menu (x86).

Booting from the Network Using PXE

To boot with PXE, you need a properly configured TFTP server, and a network interface in your computer that supports PXE. For information on how to configure a PXE server, see Preparing for a Network Installation.

Configure the computer to boot from the network interface. This option is in the BIOS, and can be labeled Network Boot or Boot Services. Also, ensure that the BIOS is configured to boot first from the correct network interface. Some BIOS systems specify the network interface as a possible boot device, but do not support the PXE standard. See your hardware’s documentation for more information. Once you properly enable PXE booting, the computer can boot the CentOS installation system without any other media.

Follow the procedure below to boot the installation program from a PXE server. Note that this procedure requires the use of a physical network connection, for example Ethernet. It will not work with a wireless connection.

Booting the Installation from the Network Using PXE

Ensure that the network cable is attached. The link indicator light on the network socket should be lit, even if the computer is not switched on.
Switch on the computer.
Depending on your hardware, some network setup and diagnostic information can be displayed before your computer connects to a PXE server. Once it connects, a menu is displayed according to the configuration of the PXE server. Press the number key that corresponds to the desired option. If you are not sure of which option to select, ask your server administrator.

At this point, the installation program starts successfully and the boot screen appears, which contains information on a variety of boot options. Installation program automatically begins if you take no action within the first minute. For a description of the options available on this screen, see The Boot Menu (x86).

Once your system has completed loading the boot media, a boot menu is displayed using GRUB2 (GRand Unified Bootloader, version 2). The boot menu provides several options in addition to launching the installation program. If no key is pressed within 60 seconds, the default boot option (the one highlighted in white) will be run. To choose the default, either wait for the timer to run out or press Enter.

Figure 1. The Boot Screen

To select a different option than the default, use the arrow keys on your keyboard, and press Enter when the correct option is highlighted.

To customize the boot options for a particular menu entry:

On BIOS-based systems, the preferred way is to press the Tab key and add custom boot options to the command line. You can also access the boot: prompt by pressing the Esc key but no required boot options will be preset in it. In that case, you must always specify the linux option before using any other boot options.
On UEFI-based systems, press the e key and add custom boot options to the command line. When ready press Ctrl+X to boot the modified option.

See Boot Options for more information about additional boot options.

The boot menu options are:

Install CentOS 7: Choose this option to install CentOS onto your computer system using the graphical installation program.
Test this media & install CentOS 7: This option is the default. Prior to starting the installation program, a utility is launched to check the integrity of the installation media.
Troubleshooting >: This item is a separate menu containing options that help resolve various installation issues. When highlighted, press Enter to display its contents.

Figure 2. The Troubleshooting Menu

Install CentOS 7 in basic graphics mode: This option allows you to install CentOS in graphical mode even if the installation program is unable to load the correct driver for your video card. If your screen appears distorted or goes blank when using the Install CentOS 7 option, restart your computer and try this option instead.
Rescue a CentOS system: Choose this option to repair a problem with your installed CentOS system that prevents you from booting normally. The rescue environment contains utility programs that allow you fix a wide variety of these problems.
Run a memory test: This option runs a memory test on your system. For more information, see Loading the Memory Testing Mode.
Boot from local drive: This option boots the system from the first installed disk. If you booted this disc accidentally, use this option to boot from the hard disk immediately without starting the installation program.