Chapter 5
Installing and Maintaining Software in Red Hat

Installing and maintaining software on Red Hat–based servers is similar to the Ubuntu server process, just with different tools. Just like Ubuntu, Red Hat uses a package management system to make installing and updating software easy, especially if your server is connected to the Internet. However, if your Red Hat server is not connected to the Internet, there's still a way for you to install and upgrade software using packages.

Exploring Red Hat Packages

Red Hat Enterprise Linux, CentOS, and Fedora use the Red Hat Package Manager (RPM) utility to install and manage software. Application files are bundled into an rpm package for distribution. rpm package files have an .rpm file extension and use a specific naming format as follows:

name-version-release.architecture.rpm

Since software packages are compiled for specific architectures, there are usually multiple rpm packages for each software package. The version is the program's version number, so you can easily track what version of the software is currently installed and what version is available for download. The release is the distribution release identifier. Even though rpm packages can be installed on any Red Hat–based Linux system, sometimes packages are compiled for specific distribution environments. Packages created for CentOS normally have a release of el8. Here's an example of listing some .rpm files:

# ls -l *.rpm
total 11920
drwxr-xr-x. 2 sysadmin sysadmin     253 Dec  5 10:23 .
drwx------. 3 sysadmin sysadmin      74 Dec  5 10:21 ..
-rwxr-x---. 1 sysadmin sysadmin 1621792 Dec  5 10:21 bash-4.4.19-10.el8.x86_64.rpm
-rwxr-x---. 1 sysadmin sysadmin 5943540 Dec  5 10:21 binutils-2.30-73.el8.x86_64.rpm
-rwxr-x---. 1 sysadmin sysadmin  361000 Dec  5 10:21 curl-7.61.1-12.el8.x86_64.rpm
-rwxr-x---. 1 sysadmin sysadmin  507956 Dec  5 10:21 openssh-8.0p1-4.el8_1.x86_64.rpm
-rwxr-x---. 1 sysadmin sysadmin  713708 Dec  5 10:21 openssl-1.1.1c-15.el8.x86_64.rpm
-rwxr-x---. 1 sysadmin sysadmin 3039264 Dec  5 10:21 zsh-5.5.1-6.el8_1.2.x86_64.rpm
#

Notice that the architecture for each is x86_64, indicating that the software packages were compiled for a 64‐bit CPU environment.

There are two ways to install rpm packages.

  • Using an automated package management tool
  • Manually using the rpm command‐line tool

Using an automated package management tool is usually preferred. These tools have the ability to connect via the Internet to a software repository to find the requested package and install it, along with any dependent packages. However, there are times when a Red Hat server doesn't have Internet access, such as in secure environments. In those cases, you'll have to download the software rpm packages on a different platform, transfer them to the server, and then install them manually using the rpm command‐line tool. The following sections cover both methods of installing RPM software packages.

Automated Package Management

Like the Debian‐based distributions, the Red Hat–based systems have several different front‐end tools available. The common ones are these:

  • yum : Used in Red Hat, CentOS, and Fedora
  • dnf : An updated version of yum with some additional features
  • zypper : Used in openSUSE

These front ends are all based on the rpm command‐line tool. The following section discusses how to manage software packages using these various rpm ‐based tools. The focus will be on dnf, but the other packages use similar commands and formats.

Listing Installed Packages

To find out what is currently installed on your system, at the shell prompt use the list option of the dnf command, as shown here:

$ dnf list installed
Installed Packages
NetworkManager.x86_64                 1:1.22.8-5.el8_2                     @BaseOS
NetworkManager-config-server.noarch   1:1.22.8-5.el8_2                     @BaseOS
NetworkManager-libnm.x86_64           1:1.22.8-5.el8_2                     @BaseOS
NetworkManager-team.x86_64            1:1.22.8-5.el8_2                     @BaseOS
NetworkManager-tui.x86_64             1:1.22.8-5.el8_2                     @BaseOS
PackageKit.x86_64                     1.1.12-4.el8                         @AppStream
PackageKit-glib.x86_64                1.1.12-4.el8                         @AppStream
abattis-cantarell-fonts.noarch        0.0.25-4.el8                         @AppStream
acl.x86_64                            2.2.53-1.el8                         @BaseOS
adcli.x86_64                          0.8.2-5.el8                          @BaseOS
at.x86_64                             3.1.20-11.el8                        @BaseOS
attr.x86_64                           2.4.48-3.el8                         @BaseOS
audit.x86_64                          3.0-0.17.20191104git1c2f876.el8      @BaseOS
audit-libs.x86_64                     3.0-0.17.20191104git1c2f876.el8      @BaseOS
…
$

There will be lots of packages installed on your server; it usually helps to redirect the output to the more or less command to look at the list in a controlled manner. You can also redirect the output to a text file for viewing in a text editor.

dnf list installed > installed.txt

The format of the listing is a little different from the format of the original package names, but you can probably pick out the different components. The package name and architecture are listed first, followed by the version and release. The third column shows what repository category the package came from.

You can also look for a single installed package.

$ dnf list installed bash
Installed Packages
bash.x86_64                          4.4.19-10el8                       @BaseOS
$

If the package isn't installed, dnf will tell you.

$ dnf list installed zsh
Error: No matching Packages to list
$

You can then check if the package is available in the software repository by using the list option with the software package name.

$ dnf list zsh
Last metadata expiration check: 0:00:18 ago on Sat 05 Dec 2020 10:33:03 AM EST.
Available Packages
zsh.x86_64                        5.5.1-6.el8_1.2                         BaseOS
$

Finally, if you need to find out what software package provides a particular file on your filesystem, use the provides option.

dnf provides file_name

Here's an example of trying to find what software provided the file /usr/bin/gzip :

$ dnf provides /usr/bin/gzip
Last metadata expiration check: 0:04:02 ago on Sat 05 Dec 2020 10:32:22 AM EST.
gzip-1.9-9.el8.x86_64 : The GNU data compression program
Repo        : @System
Matched from:
Filename    : /usr/bin/gzip
 
gzip-1.9-9.el8.x86_64 : The GNU data compression program
Repo        : BaseOS
Matched from:
Filename    : /usr/bin/gzip
$

dnf checked two separate repositories: the local system (denoted by @System) and the default fedora repository (denoted by BaseOS). That allows you to easily check whether there's an update available for the file.

Installing Software with dnf

Installation of a software package using dnf is simple. All you need is the install option, followed by the package name.

dnf install package_name

This installs not only the software package specified, but also any package dependencies. The output will show you the package information, along with any dependent packages required to install, and prompt you to continue the installation.

Upgrading Software with dnf

In most Linux distributions, when you're working away in the graphical user interface (GUI), you get those nice little notification icons telling you a software upgrade to a new version is needed. Here at the command line, it takes a little more work.

To see the list of all the available upgrades for your installed packages, type the following command:

dnf list upgrades

If you see that a particular software package needs upgrading, then type in the following command:

dnf upgrade package_name

If you'd like to upgrade all the packages listed in the upgrade list, just enter the following command:

dnf upgrade

One nice feature in dnf is the upgrade‐minimal command. It upgrades a package to the latest bug fix or security patch version instead of the latest and greatest version.

Uninstalling Software with dnf

The dnf tool also provides an easy way to uninstall software you no longer need by using the remove option.

# dnf remove zsh
Dependencies resolved.
==============================================================================
 Package      Architecture    Version                  Repository        Size
==============================================================================
Removing:
 zsh          x86_64          5.5.1-6.el8_1.2          @BaseOS          7.2 M
 
Transaction Summary
==============================================================================
Remove  1 Package
 
Freed space: 7.2 M
Is this ok [y/N]: y
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                      1/1
  Running scriptlet: zsh-5.5.1-6.el8_1.2.x86_64                           1/1
  Erasing          : zsh-5.5.1-6.el8_1.2.x86_64                           1/1
  Running scriptlet: zsh-5.5.1-6.el8_1.2.x86_64                           1/1
  Verifying        : zsh-5.5.1-6.el8_1.2.x86_64                           1/1
Installed products updated.
 
Removed:
  zsh-5.5.1-6.el8_1.2.x86_64
 
Complete!
#

Unlike the Ubuntu apt tool, dnf doesn't provide an option to remove the application files but keeps any configuration or data files. When you remove a package, everything associated with that package is removed.

Handling Broken Dependencies

Sometimes as multiple software packages get loaded, a software dependency for one package can get overwritten by the installation of another package. This is called a broken dependency.

If this should happen on your system, first try the following command:

dnf clean all

Then try to use the upgrade option in the dnf command. Sometimes, just cleaning up any misplaced files can help.

If that doesn't solve the problem, try the following command:

dnf repoquery --deplist package_name

This command displays all the package's library dependencies and what software package provides them. Once you know the libraries required for a package, you can then install them. Here's an example of determining the dependencies for the zsh package:

# dnf repoquery --deplist zsh
CentOS Linux 8 - AppStream                      1.3 MB/s | 6.2 MB     00:04
CentOS Linux 8 - BaseOS                         867 kB/s | 2.3 MB     00:02
package: zsh-5.5.1-6.el8_1.2.x86_64
  dependency: /bin/sh
   provider: bash-4.4.19-12.el8.x86_64
  dependency: coreutils
   provider: coreutils-8.30-8.el8.x86_64
  dependency: grep
   provider: grep-3.1-6.el8.x86_64
  dependency: info
   provider: info-6.5-6.el8.x86_64
  dependency: libc.so.6(GLIBC_2.15)(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libdl.so.2()(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libdl.so.2(GLIBC_2.2.5)(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libgdbm.so.6()(64bit)
   provider: gdbm-libs-1:1.18-1.el8.x86_64
  dependency: libm.so.6()(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libm.so.6(GLIBC_2.2.5)(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libm.so.6(GLIBC_2.23)(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libncursesw.so.6()(64bit)
   provider: ncurses-libs-6.1-7.20180224.el8.x86_64
  dependency: libpcre.so.1()(64bit)
   provider: pcre-8.42-4.el8.x86_64
  dependency: librt.so.1()(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: librt.so.1(GLIBC_2.2.5)(64bit)
   provider: glibc-2.28-127.el8.x86_64
  dependency: libtinfo.so.6()(64bit)
   provider: ncurses-libs-6.1-7.20180224.el8.x86_64
  dependency: rtld(GNU_HASH)
   provider: glibc-2.28-127.el8.i686
   provider: glibc-2.28-127.el8.x86_64
#

As you can see from the output, there are lots of different packages that must be installed for the Z shell to work properly. Good thing dnf ensured they were all installed for us!

Working with RPM Repositories

Just like the apt systems, dnf has its software repositories set up at installation. For most purposes, these preinstalled repositories will work just fine for your needs. But if and when the time comes that you need to install software from a different repository, here are some things you will need to know.

To see what repositories you are currently pulling software from, use the repolist option.

# dnf repolist
repo id                         repo name
appstream                       CentOS Linux 8 - AppStream
baseos                          CentOS Linux 8 - BaseOS
extras                          CentOS Linux 8 - Extras
#

If you don't find a repository you need software from, then you will need to do a little configuration file editing. There are two places where the dnf repository definitions can be located.

  • In the /etc/dnf/dnf.conf configuration file
  • As separate files in the /etc/yum.repos.d directory

Good repository sites such as rpmfusion.org will lay out all the steps necessary to use them. Sometimes these repository sites will offer an RPM file that you can download and install. The installation of the RPM file will do all the repository setup work for you!

Working Directly with Packages

There may be some environments where your Linux server won't have Internet access to contact the repository to automatically download packages. For example, often high‐security environments block all network traffic except internal traffic. In these environments, you'll need a way to manually install or update software packages.

The main tool for working with .rpm files is the rpm program. The rpm utility is a command‐line program to install, modify, and remove .rpm software packages. Its basic format is as follows:

rpm action [OPTION] package

Table 5.1 describes the actions for the rpm command.

TABLE 5.1: The rpm Command Actions

SHORT LONG DESCRIPTION
‐e ‐‐erase Removes the specified package
‐F ‐‐freshen Upgrades a package only if an earlier version already exists
‐i ‐‐install Installs the specified package
‐q ‐‐query Queries if the specified package is installed
‐U ‐‐upgrade Installs or upgrades the specified package
‐V ‐‐verify Verifies if the package files are present and the package's integrity

The following sections show how to use the rpm command to manually manage software packages.

Finding Package Files

If you need to obtain copies of RPM files on a Red Hat–based distro, such as CentOS or Fedora, you have a few different options. If you have a separate Linux system connected to the Internet, use the yumdownloader utility. This downloads a specified rpm package file directly from the repository. The yumdownloader tool is part of the yum‐utils package, which you'll most likely need to install first; then you can download any rpm package from the repository.

$ yumdownloader zsh
Last metadata expiration check: 0:21:30 ago on Sat 05 Dec 2020 08:49:35 AM EST.
zsh-5.5.1-6.el8_1.2.x86_64.rpm                  1.1 MB/s | 2.9 MB     00:02
 
$ ls -l zsh*
-rw-r--r--. 1 root root 3039264 Dec  5 09:11 zsh-5.5.1-6.el8_1.2.x86_64.rpm
$

The other method for obtaining rpm package files is using the distribution website. Most Linux distributions provide direct access to RPM files used in the distribution via a download site. For CentOS, click the RPMs link on the Download page (mirror.centos.org/centos/8 / at the time of this writing), next to the distribution version you have installed on the server. This takes you to a repository of all the current rpm packages for that distribution.

Inspecting Package Files

Use the ‐q action to perform a simple query on the package management database for installed packages.

$ rpm -q bash
bash-4.4.19-12.el8.x86_64
$ rpm -q zsh
package zsh is not installed
$

There are several options you can add to the query action to obtain more detailed information. Table 5.2 shows a few of the more commonly used query options.

TABLE 5.2: The rpm Command Query Action Options

SHORT OPTION LONG OPTION DESCRIPTION
‐c ‐‐configfiles Lists the names and absolute directory references of package configuration files
‐i ‐‐info Provides detailed information, including version, installation date, and signatures
N/A ‐‐provides Shows what facilities the package provides
‐R ‐‐requires Displays various package requirements (dependencies)
‐s ‐‐state Provides states of the different files in a package, such as normal (installed), not installed, or replaced
N/A ‐‐what‐provides Shows to what package a file belongs

You can also add the ‐i action, which provides a detailed list of information on the package.

$ rpm -qi bash
Name        : bash
Version     : 4.4.19
Release     : 12.el8
Architecture: x86_64
Install Date: Sat 05 Dec 2020 08:43:49 AM EST
Group       : Unspecified
Size        : 6861588
License     : GPLv3+
Signature   : RSA/SHA256, Tue 21 Jul 2020 12:08:45 PM EDT, Key ID 05b555b38483c65d
Source RPM  : bash-4.4.19-12.el8.src.rpm
Build Date  : Tue 21 Jul 2020 12:03:55 PM EDT
Build Host  : x86-02.mbox.centos.org
Relocations : (not relocatable)
Packager    : CentOS Buildsys <bugs@centos.org>
Vendor      : CentOS
URL         : https://www.gnu.org/software/bash
Summary     : The GNU Bourne Again shell
Description :
The GNU Bourne Again shell (Bash) is a shell or command language
interpreter that is compatible with the Bourne shell (sh). Bash
incorporates useful features from the Korn shell (ksh) and the C shell
(csh). Most sh scripts can be run by bash without modification.
$

From the output of the detailed query, you can see specific information, such as the date the package was installed and a brief description of the package.

Installing Package Files

There are a couple of ways to install an rpm package that you have downloaded. For a new package, use the ‐i action to install the package. However, if an older version of the package already exists on your system, you'll receive an error message.

It's more common to use the ‐U action, which installs the new package, or upgrades the package if it's already installed on the system. It has also become somewhat common to add the ‐vh options as well. The ‐h option shows the progress of the update, and the ‐v option shows what it's doing.

rpm -Uvh package

It's also important to remember that you must have root privileges to manually install packages, either as the root user or as a user account with root privileges.

Even though you installed the zsh package using the rpm command‐line tool, it appears when you use the dnf command to list the installed packages. This shows that both commands install packages to the same package management database.

Removing Package Files

To remove an installed package, just use the ‐e action for the rpm command.

# rpm -e zsh
# rpm -q zsh
package zsh is not installed
# dnf list installed zsh
Error: No matching Packages to list
#

The ‐e action doesn't show if it was successful, but it will display an error message if something goes wrong with the removal. You can check to make sure the removal was successful by using the ‐q action to query the package database or by using the dnf list installed command.

Using Flatpak Containers

As discussed in Chapter 3, “Installing and Maintaining Software in Ubuntu,” containers are software packaging systems that bundle all the files required to run an application into a single package. While this creates duplication of files, it helps eliminate the issue of conflicting library files and makes it easier to move application containers around between servers.

The flatpak application container format was created as an independent open source project with no direct ties to any specific Linux distribution. That said, battle lines have already been drawn, with Red Hat, CentOS, and Fedora oriented toward using flatpak instead of Canonical's snap container format.

While CentOS desktop distributions install flatpak by default, the CentOS server environment doesn't. However, you can easily install flatpak as a package using the standard dnf or rpm methods.

To find an application in the flatpak repository, you use the flatpak search command.

# flatpak search mosh
Name     Description          Application ID     Version    Branch    Remotes
Mosh     The Mobile Shell     org.mosh.mosh      1.3.2      stable    flathub
#

When working with a container, you must use its Application ID value and not its name. To install the application, use the flatpak install command.

# flatpak install org.mosh.mosh
Looking for matches…
Found similar ref(s) for 'mosh' in remote 'flathub' (system).
Use this remote? [Y/n]: y
Found ref 'app/org.mosh.mosh/x86_64/stable' in remote 'flathub' (system).
Use this ref? [Y/n]: y
Required runtime for org.mosh.mosh/x86_64/stable (runtime/org.freedesktop.Platform/x86_64/20.08) found in remote flathub
Do you want to install it? [Y/n]: y
…
Installation complete.
#

To check whether the installation went well, you can use the flatpak list command again.

# flatpak list
Name                Application ID                   Version  Branch Installation
Freedesktop Plat… org.freedesktop.Platform           20.08.2  20.08  system
default           …freedesktop.Platform.GL.default            20.08  system
openh264          …g.freedesktop.Platform.openh264   2.1.0    2.0    system
Mosh              org.mosh.mosh                      1.3.2   stable  system
#

Finally, to remove an application container, use the flatpak uninstall command.

# flatpak uninstall org.mosh.mosh
 
        ID                  Branch      Op
 1. [-] org.mosh.mosh       stable      r
 
Uninstall complete.
#

Using application containers is similar to using package management systems, but what goes on behind the scenes is fundamentally different. However, the end result is that you have an application installed on your Linux system that can be easily maintained and upgraded.

The Bottom Line

  • Recognize Red Hat packages. Developers bundle the files required for an application into a package to make it easier to install. A package management system allows you to easily track what software packages are installed on your Linux system, as well as install, update, and remove them. Red Hat–based Linux distributions use the Red Hat Package Management (RPM) system for managing application software. The rpm command‐line tool provides access to the package management database, allowing you to quickly determine the status of installed packages.
    • Master It The curl software package allows you to easily transfer data using a multitude of protocols (such as FTP, HTTP, and SCP) from the command line. What command would you use to determine whether curl is installed on your Linux system? If the package is installed, what command would you use to view the version and a description of the package?
  • Use automated Red Hat package managers. Most Red Hat–based Linux distributions are based on the rpm utility but use different front‐end tools at the command line. Red Hat, CentOS, and Fedora use dnf for installing and managing software packages. The dnf tool automatically installs any software packages required by the package you install.
    • Master It The perf utility allows you to monitor the performance of a Linux system. What command would you use to check whether the perf software is available as an rpm package for your Linux system, and what command would you use to install it? What command would you use to remove it?
  • Manually install Red Hat packages. Not all Linux systems are connected to the Internet, allowing the automated package management tools to connect to a repository. In those situations, you'll need to manually find and download RPM software packages and then use the rpm command to manually install the package. The most common options used to install software are the ‐Uvh options, which will update the package if it's already installed and provide verbose information on the installation progress.
    • Master It What steps would you need to take to install the perf utility if your Linux system is not connected to the Internet?
  • Install flatpak application containers. Application containers are relatively new in software package management. Containers bundle all of the software required for an application to run, including all files the application is dependent on. This makes containers portable and easily moved between systems. Red Hat Linux–based distributions use the flatpak container format.
    • Master It Cointop is a terminal‐based application for tracking cryptocurrencies. What command would you use to check if there's a flatpak container for it, and what command would you use to install it?