Mastering Linux System Administration. Richard Blum

      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.

      ROGUE REPOSITORIES

      These days, it's always a good idea to stick with approved repositories. An approved repository is one that is sanctioned by the distribution's official site. If you start adding unapproved repositories, you lose the guarantee of stability. And you will be heading into broken dependencies territory.

      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