Install, update and remove software

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$ als gewone gebruiker# als root (of met sudo)

Examendoelen in dit hoofdstuk

Software installeren en bijwerken vanaf het Red Hat-netwerk, een externe repository of het lokale bestandssysteem

Understand repositories

A repository is a place (web server, folder, ISO) with packages and an index. dnf reads the index, solves the dependencies and installs everything that is needed.

A RHEL system gets the Red Hat repositories only after it is registered (subscription).
The two main repositories are BaseOS (the core OS) and AppStream (applications, languages, databases).
Repositories are described in files /etc/yum.repos.d/*.repo. Red Hat's own file is redhat.repo, managed by subscription-manager.

$dnf repolist
$dnf repolist all
$ls /etc/yum.repos.d/

Examentip

On the exam the system is normally not registered. You must create a .repo file for the repository URL they give you before you can install anything.

9.2

Register the system with Red Hat

Registration connects the system to your Red Hat account and enables the Red Hat repositories.

#subscription-manager register --username your_rh_user
#subscription-manager status
#subscription-manager repos --list-enabled
#subscription-manager repos --enable codeready-builder-for-rhel-10-x86_64-rpms

A free Red Hat Developer subscription allows up to 16 systems for learning.
subscription-manager unregister removes the system again (do it before you delete a VM).

9.3

Connect to a repository

A .repo file needs only three things: a label in [ ], a name and a baseurl. Add GPG settings to check the packages.

Create the file for each repository.

#vim /etc/yum.repos.d/exam.repo

/etc/yum.repos.d/exam.repo

[BaseOS]
name=BaseOS
baseurl=http://repo.example.com/rhel10/BaseOS
gpgcheck=0
 
[AppStream]
name=AppStream
baseurl=http://repo.example.com/rhel10/AppStream
gpgcheck=0

Or let dnf write the file for you.

#dnf config-manager --add-repo http://repo.example.com/rhel10/BaseOS

Check that dnf sees the repositories.
```
#dnf repolist
```

Key	Meaning
`baseurl`	URL of the repo: `http://`, `https://`, `ftp://` or `file:///path`
`enabled`	`1` = use it (default), `0` = do not use it
`gpgcheck`	`1` = check the package signatures
`gpgkey`	Where the public key is, like `file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release`

Let op

dnf config-manager --add-repo does not add a gpgcheck line. With the default gpgcheck=1 from /etc/dnf/dnf.conf, install fails if the key is unknown. Add gpgcheck=0 (lab only) or the right gpgkey.

9.4

Keep packages trusted

Packages are signed with a GPG key. dnf checks the signature, so nobody can give you a changed package.

#rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
$rpm -q gpg-pubkey --qf '%{NAME}-%{VERSION}-%{RELEASE}\t%{SUMMARY}\n'
$rpm -K package.rpm

Op het werk

In production keep gpgcheck=1 and repo_gpgcheck where the repository supports it. gpgcheck=0 is for labs and the exam only.

9.5

Make a repository from the installation ISO

The RHEL installation ISO contains BaseOS and AppStream with their indexes. Mount it and point a .repo file to it — a full repository without internet.

Mount the ISO for good.

#mkdir /repo
#echo "/root/rhel-10.0-x86_64-dvd.iso /repo iso9660 defaults,loop 0 0" >> /etc/fstab
#systemctl daemon-reload; mount -a

Point dnf to both folders on the ISO.

/etc/yum.repos.d/local.repo

[local-BaseOS]
name=Local BaseOS
baseurl=file:///repo/BaseOS
gpgcheck=0
 
[local-AppStream]
name=Local AppStream
baseurl=file:///repo/AppStream
gpgcheck=0

For your own RPM files, create the index with createrepo.
```
#dnf install -y createrepo_c
#createrepo /srv/myrepo
```

Controleer het

The local repositories are listed.

#dnf repolist

9.6

Find software

Search by name or description, or find the package that gives a file or command.

$dnf search nmap
$dnf search all "web server"
$dnf provides '*/semanage'
$dnf provides /usr/bin/dig
$dnf info httpd

Onthoud

"Which package has the command X?" → dnf provides */X.

9.7

Install and remove packages

dnf install adds packages with all dependencies; dnf remove removes them (and dependencies that nothing else needs).

#dnf install -y httpd
#dnf install -y ./tool-1.2-1.el10.x86_64.rpm
#dnf reinstall -y openssh-server
#dnf remove -y httpd
#dnf autoremove

-y answers yes to every question.
A local .rpm file with dnf install (not rpm -i) also installs the dependencies from the repositories.

9.8

List packages

dnf list shows installed and available packages; use patterns to narrow it down.

$dnf list installed
$dnf list available 'python3*'
$dnf list --upgrades
$dnf list 'selinux*'
$rpm -qa | wc -l

9.9

Update the system

dnf upgrade (or dnf update) installs newer versions. A new kernel is added next to the old one, so you can boot the old one if the new one fails.

#dnf check-update
#dnf upgrade -y
#dnf upgrade -y openssh-server
#dnf upgrade --security -y
$rpm -q kernel

Op het werk

Check dnf needs-restarting -r after updates: it tells you if a reboot is needed (kernel, glibc, systemd).

9.10

Install package groups

A group is a set of packages for one job, like "Development Tools" or "Server with GUI".

$dnf group list
$dnf group list --hidden
$dnf group info "Development Tools"
#dnf group install -y "Development Tools"
#dnf group remove -y "Development Tools"

9.11

Undo changes with dnf history

dnf remembers every transaction. You can see what changed and undo it.

#dnf history
#dnf history info 12
#dnf history undo 12

Notitie

undo works only if the old package versions are still in a repository.

9.12

Read RPM file names

The file name tells name, version, release, OS and architecture.

example

httpd-2.4.63-1.el10.x86_64.rpm

Part	Value
Name	`httpd`
Version (upstream)	`2.4.63`
Release (Red Hat build)	`1`
OS	`el10` = RHEL 10
Architecture	`x86_64` (or `noarch` for any)

9.13

Query installed packages with rpm

rpm -q asks the database of installed packages: which files, configs and docs a package has, and which package a file belongs to.

$rpm -qa | grep httpd
$rpm -qi httpd
$rpm -ql httpd
$rpm -qc httpd
$rpm -qd httpd
$rpm -qf /etc/ssh/sshd_config
$rpm -V openssh-server

Option	Shows
`-qa`	All installed packages
`-qi`	Information
`-ql`	All files
`-qc`	Config files only
`-qd`	Documentation files
`-qf FILE`	The package of a file
`-V`	Changed files (verify)

9.14

Look inside a package file before installing

Add -p to query an .rpm file instead of the database. Always check the scripts of a package from the internet.

$rpm -qpi tool-1.2-1.el10.x86_64.rpm
$rpm -qpl tool-1.2-1.el10.x86_64.rpm
$rpm -qp --scripts tool-1.2-1.el10.x86_64.rpm
$rpm -qpR tool-1.2-1.el10.x86_64.rpm

Let op

Package scripts run as root during the install. A bad script can do anything.

9.15

Install desktop apps with Flatpak

Flatpak installs mostly graphical apps in a sandbox, with their own runtime, independent from the RPM packages. It is not meant for server software.

Install Flatpak and add a remote (a Flatpak repository).

#dnf install -y flatpak
#flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
$flatpak remotes

Find and install an app.

$flatpak search gimp
#flatpak install -y flathub org.gimp.GIMP
$flatpak list --app

Run, update and remove it.

$flatpak run org.gimp.GIMP
#flatpak update -y
#flatpak uninstall -y org.gimp.GIMP

Installed as root = for all users (system). With --user = only for that user.
Red Hat has its own remote with RHEL apps: flatpak remote-add rhel https://flatpaks.redhat.io/rhel.flatpakrepo (needs a Red Hat login).

9.16

Remember the main points

The most important facts of this chapter, in short.

dnf installs, updates and removes packages and solves dependencies; yum is the same command.
Repositories are set in .repo files in /etc/yum.repos.d/ with baseurl, enabled and gpgcheck.
GPG keys prove that packages are real; keep gpgcheck=1 when you can.
dnf search, dnf info, dnf provides, dnf list installed find packages; dnf history shows and undoes transactions.
Package groups install sets of software: dnf group list, dnf group install "NAME".
rpm -q asks the RPM database: -qa all, -qi info, -ql files, -qf FILE which package owns a file, -qc config files.
You can make your own repository from an ISO or folder of RPMs (createrepo for a folder).
Flatpak installs desktop apps from Flathub in their own sandbox.

9.17

Learn the key terms

The words of this chapter in simple English.

Term	Meaning
Package	One file with a program, its files and data about it (RPM).
Dependency	Another package that a package needs.
Repository	A collection of packages with an index (metadata).
.repo file	The settings of a repository for dnf.
GPG key	The key that checks the signature of packages.
Package group	A set of packages for one job, like "Development Tools".
Module	An older way to offer more versions of software (AppStream).
RPM database	The list of installed packages and their files.
Transaction	One dnf action that installs, updates or removes packages.
Flatpak	A way to install desktop apps with their own runtime.