Managing Software

Nov 3, 2025 [Nov 8, 2025]
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DNF and Flatpak Use Cases

RPM, YUM, and DNF

  • In the early days, software was packaged as a tarball, and installing meant extracting the tarball and do as directed
  • Red Hat Package Manager (rpm) introduced packages on Red Hat
    • These packages contained metadata with information about required dependencies
      • A database was also added to keep track of installed packages, which made updating software easier
      • Still, dependencies needed to be resolved manually
  • When Yellowdog Update manager (YUM) was introduced, packages could be installed from repositories, and dependencies could be handled automatically
  • Dandified Yum (DNF) was mainly an internal improvement of YUM, and still used the same approach for installing packages
  • Still in DNF, packages need to be created for specific Linux OSs and architecture

Flatpak

  • Flatpak is attempting to resolve the lack of package management standardization between distributions by providing images that run isolated as a container on most Linux distributions and architectures
  • The image contains everything required to run the package
  • A Flatpak application runs in a sandbox, which isolates it from other system components by default

When to use which?

  • Flatpak is excellent for desktop applications
  • DNF is preferred for server processes and daemons that need tight integration with the server operating system

Managing RPM Packages

  • Software on RHEL is installed using packages in Red Hat (RPM) format
  • An RPM package contains a compressed archive and package metadata
  • In the metadata, package dependencies are identified
  • To automatically handle dependency management, RHEL uses dnf and repositories for package installation
  • Packages should not be installed with dnf, not rpm
  • Installed packages are registered in the RPM database
  • The rpm command can be used to list packages and analyze package content
    • rpm -qa shows all packages currently installed
    • rpm -qf filename shows from which package filename was installed
    • rpm -ql lists files installed from a package
    • rpm -q --scripts shows scripts executed while installing the package
    • rpm -q --changelog shows the changelog for a package
  • Querying package files rather than the RPM database is also possible
    • Add -p to any of the commands above
  • Contents of an RPM package can be extracted to the current directory (without installing)
    • rpm2cpio mypackage.rpm | cpio -tv will show the contents of a package
    • rpm2cpio mypackage.rpm | cpio -idmv extracts the package contents to the current directory

Exercise

  • Determine what package the file /etc/crypttab comes from
  • List the other files created from that package
  • List the configuration files associated with that package

rpm Solution

rpm -qf /etc/crypttab
rpm -ql systemd-udev
rpm -qc systemd-udev

dnf Solution

Search both installed packages and repositories

dnf provides /etc/crypttab

Query an existing file

dnf repoquery -f /etc/crypttab

List all installed package files

dnf repoquery --installed -l systemd-udev

List all files in /etc. Note that not all these are configuration files, thus, rpm -qc is a better method.

dnf repoquery --installed -l systemd-udev | grep -E '^/etc/'

Setting up Repository Access

Adding a repository that exists on the filesystem

dnf config-manager --add-repo="file:///repo/BaseOS"
dnf config-manager --add-repo="file:///repo/AppStream"

Adding a repository over http

dnf config-manager --add-repo="http://server.com/repo/BaseOS"
dnf config-manager --add-repo="http://server.com/repo/AppStream"

During the exam there is no internet access so repository GPG keys cannot be checked. Add gpgcheck=0 to the repo file(s) in /etc/yum.repos.d.

cat >> /etc/yum.repos.d/AppStream.repo << EOF
[AppStream]
name=AppStream
baseurl=file:///repo/AppStream
gpgcheck=0
EOF

Managing packages with dnf

  • dnf list lists installed and available packages
    • dnf list 'selinux*'
  • dnf search searches name and summary dnf search all searches in description as well
    • dnf search seinfo
    • dnf search all seinfo
  • dnf provides searches in package file lists for the package that provides a specific file
    • dnf provides */Containerfile will list all packages that have a file Containerfile
  • dnf info shows information about a package
  • dnf install installs packages as well as any dependencies
  • dnf remove removes packages as well as dependencies
  • dnf update compares current package version with the package version listed in the repository and updates if necessary
    • dnf update kernel will install the new kernel and keeps the old as a backup

Using dnf groups

  • A dnf group is a collection of packages
  • A regular group is just a collection of packages
  • An environment group is used to install a specific usage pattern, and may consist of packages and groups
  • Use dnf group list to see a list of groups
  • Some groups are normally only installed through environment groups and not separately, and for that reason don’t show in dnf group list
  • dnf group info to see packages within a group
  • dnf group install to install only mandatory and default packages
    • dnf group install --with-optional to install optional as well

Managing dnf updates and history

  • dnf history list lists dnf transactions
  • dnf history undo to undo a transaction from the list (AMAZING)
  • dnf history --help for a list of options

Subscription Manager

DO NOT DO THIS FOR PRACTICE VMs

  • To register, use subscription-manager register
  • To unregister, use subscription-manager unregister
    • After registering, entitlement certificates are created
      • /etc/pki/product indicates the installed Red Hat products
      • /etc/pki/consumer identifies the Red Hat account for registration
      • /etc/pki/entitlement indicates which subscription is attached
  • Use rct to check current entitlements

Flatpak ‘remotes’

  • To get access to the default Flatpak repository, you must authenticate using podman login registry.redhat.io
  • To make the login persistent for the current user, use the following command:
    • cp $XDG_RUNTIME_DIR/containers/auth.json $HOME/.config/flatpak/oci-auth.json
  • Flatpak uses remote repositories (“remotes”) to install packages
  • Remotes are stored in /etc/flatpak/remotes.d
  • Red Hat has its own remote repository, otherwise the repository at https://flathub.org is commonly used
  • Use flatpak remotes to print a list of the remote repositories that are available
  • To add a remote, use
    • flatpak remote-add --if-not-exists fedora oci+https://registry.fedoraproject.org
    • flatpak remote-add --if-not-exists {remote-name} {remote-url}
  • flatpak remotes --system lists remotes available to everyone
  • flatpak remotes --user lists remotes available to this user only
  • flatpak remote-ls {remote} lists applications available in the remote repository

Managing Flatpak applications

  • flatpak search
  • flatpak install
    • flatpak install -u to install an application for the current user only
  • flatpak list shows applications currently installed
  • flatpak info
  • flatpak update
  • To ensure that an application won’t be updated, use flatpak mask
    • Use flatpak mask --remove to remove the mask
  • flatpak uninstall [--delete-data] uninstalls and optionally deletes application data

Lab Exercise

  1. Ensure your system is using an offline repository for base packages as well as application streams
  2. Find the package that contains the seinfo program file and install it
  3. Install Firefox as a flatpak application
Solution
  1. —
  2. dnf provides seinfo; dnf install ...
  3. — 
    flatpak remote-add --if-not-exists fedora oci+https://registry.fedoraproject.org
flatpak search firefox
flatpak install fedora org.mozilla.firefox

- Clint Jordan