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While managing your server, you’ll sometimes need to check on which software (or packages) you have installed on your system. You’ll need to know package names, version numbers, dates of installation, etc. In this Liquid Web tutorial, we’re going to be discussing how to inspect packages installed on your CentOS system. There are several ways to accomplish this, and we’ll discuss a few of them. Let’s dig in! To use these commands, you’ll need to log in to your server via SSH. For more information, see Logging into Your Server via Secure Shell (SSH)
Using RPM Package Manager
This first command uses the rpm package manager to poll for installed packages. This command allows you to see every installed package on your system, along with the version that is currently installed:
Note the -q means “query” and -a means “all”. We’re asking rpm to query all installed packages.
Let’s examine a small portion of the results in detail. Note that you might not have these specific packages installed on your CentOS server. The important thing here is to understand how to read the output. Take a look at a small excerpt of entries from the list.
Each entry can be broken up into three parts. From left to right, these are:
Package name: (kpartx)
Instead of displaying all installed packages, rpm can also be used to search for a single package. Let’s use rpm to query kpartx:
rpm -q kpartx
You’ll see the output displays the same package name and version we saw from rpm -qa.
Using Yum to Check Installed Packages
Using rpm is not the only way to check for installed packages on your system. Now we will discuss how to use “yum” to accomplish the same task. Try the following command:
yum list installed
You will see that the list yum provides is formatted slightly differently. Let’s look at an entry in depth.
whois.x86_64 5.1.1-2.el7 @base
The first column shows the package name and architecture: (whois.x86_64).
The second column shows the version installed: (5.1.1-2.el7).
Finally the third column shows the repository the software was installed from: (@base).
Using Yum to View Historical Installation Data
We can also use yum to view historical installation data on your system. Run the following command to see a list of anytime yum was used to install, remove, or upgrade a package:
Here is an example of the output you might see. Your system will show different results here, and that is OK. We’re just interested in learning how to read the output.
ID | Command line | Date and time | Action(s) | Altered
10 | upgrade | 2019-06-01 04:13 | I, U | 12 EE
9 | install whois | 2019-05-04 17:40 | Install | 1
8 | install python36 | 2019-05-03 21:23 | Install | 2
7 | install epel-release | 2019-05-03 21:02 | Install | 1
6 | install bind-utils | 2019-05-03 19:33 | Install | 2
5 | install docker-ce docker | 2019-05-03 17:37 | Install | 4
4 | install yum-utils yum-co | 2019-05-03 17:26 | Install | 6
3 | install git | 2019-05-03 17:19 | Install | 4
2 | install vim | 2019-05-03 17:18 | Install | 31
1 | update | 2019-05-03 17:09 | I, U | 57
Notice the column headings: “ID number, Data and time, Action(s), and Altered.” This is a good summary of when yum was used, but it is lacking detailed information. Let’s examine one of these history entries in detail. Try the following command, replacing “ID_NUMBER” with the actual ID you want to inspect.
yum history info ID_NUMBER
Here is some example output:
Loaded plugins: fastestmirror
Transaction ID : 9
Begin time : Sat May 4 17:40:24 2019
Begin rpmdb : 356:8ab21eca9f4a219812e33c41a73fbd4eb7de1ed8
End time : (0 seconds)
End rpmdb : 357:cf2bf4588ba4d3263d1c9af051c3bcc525596a68
User : Cloud User <centos>
Return-Code : Success
Command Line : install whois
Transaction performed with:
Installed rpm-4.11.3-35.el7.x86_64 installed
Installed yum-3.4.3-161.el7.centos.noarch installed
Installed yum-plugin-fastestmirror-1.1.31-50.el7.noarch installed
Install whois-5.1.1-2.el7.x86_64 @base
In this tutorial, we discussed how to use rpm and yum to search your CentOS server for installed packages. These utilities are both critical tools for Linux sysadmins on CentOS systems. Of course if you have any questions about how to use these utilities on your own Liquid Web server, let us know! The Most Helpful Humans in Hosting are standing by 24×7 and we’ll be happy to answer your questions.