In this recipe, we will learn how to download and confirm the checksum of one or more CentOS 7 disk images using a typical Windows or OS X desktop computer. CentOS is made available in various formats by HTTP, FTP, or the rsync protocol from a series of mirror sites located across the world or via the BitTorrent network. For downloading very important files from the Internet, such as operating system images, it is considered best practices to validate those files' checksum, in order to ensure that any resulting media would function and perform as expected when installing. This also makes certain that the files are genuine and come from the original source.
To complete this recipe, it is assumed that you are using a typical Windows-based (Windows 7, Windows Vista, or similar) or OS X computer with full administration rights. You will need an Internet connection to download the required installation files and also need access to a standard DVD/CD disk burner with the appropriate software, in order to create the relevant installation disks from the image files. For the purpose of this recipe, it is assumed that all the downloads will be stored on Windows in your personal C:Users<username>Downloads
folder, or if using an OS X system, in the /Users/<username>/Downloads
folder.
Regardless of the type of installation files you download, the following techniques can be applied to all the image files supplied by the CentOS project:
7
. Next, you will see an additional list of directories, such as atomic
, centosplus
, cloud
, and so on. We proceed by choosing the isos
directory.x86_64
, which is a container for the 64-bit version.md5sum.txt
.XXXX
is the month stamp of this release):CentOS-7-x86_64-Minimal-XXXX.iso
md5sum.exe
.cd downloads dir
cd ~/Downloads ls
XXXX
month stamp accordingly):md5sum.exe CentOS-7-x86_64-Minimal-XXXX.iso
md5 CentOS-7-x86_64-Minimal-XXXX.iso
d07ab3e615c66a8b2e9a50f4852e6a77 CentOS-7-x86_64-Minimal-1503-01.iso
md5sum.txt
(open in a text editor). If both the numbers match, then you can be confident that you have indeed downloaded a valid CentOS image file. If not, your downloaded file is probably corrupted, so please restart this procedure by downloading the image file again.So what have we learned from this experience?
The act of downloading a CentOS installation image is just the first step towards building the perfect server. Although this process is very simple, many do forget the need to confirm the checksum. In this book, we will work with the minimal installation image, but you should be aware that there are other installation options available to you, such as NetInstall, DVD, Everything, and various LiveCDs.