Installing CentOS from USB

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In this tutorial we will learn how to download and confirm the checksum of one or more CentOS 6 disk image(s) using a typical Windows desktop computer on a USB drive.

CentOS is made available in various formats by HTTP, FTP, or via a Torrent-based client from a series of mirror sites located across the world. It supports both the 32-bit and 64-bit architectures, and having downloaded one or more image files, it is often a good idea to validate those files’ checksum in order to ensure that any resulting media should function and perform as expected.

Download and copy CentOS on USB drive

Let’s assume that you are using a typical Windows-based computer (Windows 7, Windows Vista, or similar) with full administration rights. You will need an Internet connection to download the required installation files and access to a USB drive with the appropriate software in order to create the relevant installation disks.

Regardless as to what type of installation files you download, the following techniques can be applied to all image files supplied by the CentOS project:

1. So let’s begin by visiting http://www.centos.org/mirrors-list in your browser, or you can simply visit http://www.centos.org and navigate to Downloads | Mirrors | CentOS Public Mirror List or review the links associated with the latest release announcements made on the home page.

2. The mirror sites are categorized, so from the resulting list of links, choose a mirror that best suits your current location. For example, if you are in London (UK), you can choose European Mirrors (Countries N-Z).

3. From the resulting list and depending on your preferred method of downloading the CentOS images, scroll down and choose a mirror site by selecting either, the HTTP or the FTP link.

4. Having made your selection, you will now see a list of directories or folders that will allow you to choose the version of CentOS you want to install. To proceed, simply select the appropriate folder that reads 6.X, where X is the required minor release of CentOS 6.

5. Having chosen the preferred minor release of CentOS you want to install, you will now see an additional list of directories that includes centosplus, contrib, cr, extras, fasttrack, isos, os, and updates. To proceed, choose the isos directory.

6. At this point you are now given the opportunity to choose the preferred architecture. The directory labeled  i386 is a container for the 32-bit version while the directory labeled  x86_64 is a container for the 64-bit version. Make the appropriate selection to proceed.

7.  You will now be presented with a series of files available for download. Begin by downloading a copy of the valid checksum result labeled or identified as md5sum.txt

Note: As this is a standard text file, place your mouse on the link, right-click and choose Save As to download a copy of md5sum.txt. When finished, store this file in a safe place for future reference. For the purpose of this recipe, it is assumed that all downloads will be stored in your C:\Users\<username>\Downloads folder.

8. Now, depending on which installation image best suits your needs, start downloading the relevant file(s) in the usual way.

9. When you have finished downloading the required files, visit http://mirror.centos.org/centos/dostools/ in your browser.

10. Now download the following DOS-based tool in order that we can use it to validate our
installation files: md5sum.exe

11. It is assumed that you have downloaded all the files to the typical downloads folder
of the current user profile on your USB drive ( example: F: ), so when the download is complete, open Command Prompt (typically found at Start | All Programs | Accessories | Command Prompt) and type the following command to access this location:

cd downloads

12. To see the list of files and the relevant extensions, type the following command:

dir

The command prompt should now list all the files in your download folder (including all image files, md5sum.txt , and md5sum.exe ). Based on the file names shown, modify the following command in order to check the checksum of your ISO image file and type:

md5sum.exe your_image_file_name_here.iso

14. Press the Return key to proceed and then wait for the command prompt to respond. The response is known as the sum and the result could look like this:

087713752fa88c03a5e8471c661ad1a2 *CentOS-6.X-x86_64-minimal.iso

15. Now look at the value given, this is known as the sum, and compare against the relevant listing for your particular image file listed in md5sum.txt . If both numbers match, then you can be confident that you have indeed downloaded a valid CentOS image file.

16. Now repeat this process for any remaining image files and when you have finished, simply copy your image file(s) to the USB drive, if you’ve performed those modification on the  download folder instead of your USB drive.

See also:

  • CentOS project home page: http://www.centos.org
  • CentOS project – mirror list: http://www.centos.org/mirrors-list
  • CentOS project – approved vendors: http://www.centos.org/vendors
  • CentOS project – download FAQ regarding md5 checksum:
    http://www.centos.org/modules/smartfaq/faq.php?faqid=46
  • CentOS project – how to burn an ISO image: http://www.centos.org/docs/5/html/CD_burning_howto.html
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