All right, so now that you're familiar with repositories, let's talk about the installation commands. I'm going to address this only from the Red Hat perspective and I've been doing that mostly as we've gone along. The commands for Suse and Linux and Ubuntu or Debian-based Linux variants are different. Now, for reference, I'll mention that Suse uses Zypper, Z-Y-P-P-E-R, can use Yum as well in some cases, and Ubuntu and Debian-based variants use APT, A-P-T or Apt-get, A-P-T dash get. So focusing on the Red Hat derived variants though, as you see on the graphic, there are three commands to become familiar with and really, it's only two because you see that Yum is built on the latest DNF technology. Now understand that it's Yum version 4 that's built on DNF, starting with Red Hat Enterprise Linux version 8. If you're before RHEL 8 Yum is still there and DNF is most likely still there, it's been around awhile. But if you're in RHEL 8 and later and the other variants that are based in that stream, you'll be using Yum and DNF together. But, all right, let's start with some definitions and function. I'll start with RPM, that's the Red Hat Package Manager. Now, RPM is the basis for software management on a Red Hat Linux system. It provides a wide array of options for handling software for installation. Let me also note that you probably won't use RPM very often, although I use it a bit when I'm querying packages say, but you're going to opt to use those front end tools that are noted on the graphic, Yum or DNF. All right. Now one of the key flags that I do use often, especially if I'm new to a system and want to understand what's installed on that system, is the minus q flag and this is used to query the installed packages. You can specify a package name with the -q to see the information about a specific package, or like I like to use, I use the -a which lists all the packages and then either pipe that output to a page tool like less, or pipe the output to grep to search for packages containing a certain string. Now, while the i flag can be used to install packages, I like using the -u flag, stands for upgrade, because it will either remove an old version and install a new version of the package or simply install the package if it's not on the system already. The example in the graphic shows the -v, the verbose output option, and the -h, hashmarks will be printed as progress indicators, as common flags to use when installing or replicating a package, I happen to use Uvh all the time. The last example I'll mention is the -e flag. Now, this removes or erases, that's what the e stands for, a package from the system. Note that it's unlikely that this is going to work the first time you run it because it won't remove a package without removing all packages that depend on it, which I do think does make sense. But of course, that can lead to a hunting expedition to find all the dependent packages and then you have to make some decisions about whether you want to de-install those, if you want to remove those guys. Fortunately, you can use a combination of the -q flag and the minus minus what requires flag to display the packages that are dependent on the package to be deleted. Now, this is a good start on RPM but at this point, I'll send you to the main page and online documentation for clear and helpful guidance on using other aspects of the RPM command because I want to move on to the commands that you're most likely going to use.
