To complete this recipe it is assumed 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 standard DVD/CD disk burner 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:

The act of downloading an installation image and validating the file's integrity is just the first step towards building the perfect server, and although the process of downloading CentOS is very simple, many do forget the need to confirm the checksum.

So what have we learned from this experience?

We began this recipe by showing you how to download CentOS by outlining the various options available to you. It is not expected that you will need to do this often, but during the course of this recipe you also learned how to navigate the CentOS Project website and select the best download location based on your current location.

Having done this, our next step was to obtain a copy of md5sum.txt before downloading the preferred image files.

The time required to complete the task of downloading the relevant files will depend largely on the speed of your Internet connection, but it was important that we obtained a copy of md5sum.exe in order to confirm file integrity and compare the value given against those listed in md5sum.txt.

The DOS-based tool was obtained from http://mirror.centos.org/centos/dostools/md5sum.exe.

Having completed these steps, we then proceed to open a command prompt session and navigate to the expected destination of all the files by typing:

cd downloads

We then proceeded to view the contents of C:\Users\<username>\Downloads by typing the following command:

dir

This action lists the filenames concerned, thereby enabling us to modify the following command in order to validate the appropriate ISO files:

md5sum.exe your_image_file_name_here.iso

The resulting response provides us with the checksum value of the file in question in order that we can compare it with the corresponding value found in md5sum.txt.

For example, the content of md5sum.txt may look like this:

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

Whereas the display in command prompt may show:

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

You should repeat this process for all image files, and if these values match, then you can be confident that your download is verified. A fact that not only reduces the chance of wasting optical disks, but with security in mind, it also implies that what you downloaded is what you were expecting to download (and not something else).

So remember, with every new release the CentOS team will update the main website and enable you to download the required image files. Unless the CentOS project states otherwise, you will only need to do this once, as all minor updates can be managed like any other operating system (discussed later in this book). However, if you do intend to download them again, then it is always a good idea to check the integrity of your image files with the md5sum checksum tool.