Setting up a Repository Access

Importance of Setting Up a Repository

• Setting up a repository is crucial because:

  • On the exam, there may be no repository access available by default.

  • The exam operates in a disconnected environment, necessitating local configurations.

Definition of a Repository

• A repository is defined as:

  • A collection of RPM (Red Hat Package Manager) packages.

  • Each repository contains an index that details the contents of that repository.

  • Repositories can be hosted through websites or created locally on a machine.

Use of DNF Command

• DNF Command (Dandified YUM):

  • Default command used in current RHEL (Red Hat Enterprise Linux) for managing packages from repositories.

  • It is an improvement above YUM (Yellowdog Updater, Modified), which was used in earlier RHEL versions.

  • DNF and YUM provide the same core functionalities but with enhanced performance in DNF.

Subscription Manager

• The Subscription Manager is essential for accessing online Red Hat repositories:

  • To access these repositories, the RHEL system must be registered through the Subscription Manager.

  • Access requires an active subscription, which can be a developer subscription.

  • On the exam, the system operates in a completely disconnected setup, making it impossible to connect to Red Hat repositories directly.

• Alternatives exist:

  • Red Hat Satellite can serve as a repository when no Internet access is available.

  • Without both Internet connection and Red Hat Satellite, manual configuration of repository access is necessary.

GPG Keys and Package Signing

• GPG (GNU Privacy Guard) Keys:

  • GPG is an open-source alternative to PGP (Pretty Good Privacy).

  • The GPG key is used to sign all package contents before installation to ensure authenticity and integrity.

  • The signature of the package is checked against the local GPG key before the installation.

• GPG Check Option:

  • For easier access to trusted repositories during the exam, setting gpgcheck=0 in the repository client file is acceptable.

  • For online repositories, GPG keys are automatically fetched upon the first contact if the repository is GPG signed.

  • In manual setups, obtaining GPG keys might not be feasible, necessitating conservative settings in the configurations.

Manually Configuring Repository Access

• Adding Repository Access via DNF:

  • To enable access to repositories through Subscription Manager:

  • Use command: dnf config-manager --enable <repository_name>.

  • For third-party repositories, you can use:

  • A .repo file located in /etc/yum.repos.d/, or

  • DNF config manager commands.

• Example Command for Local Repository Access:

  • Command: dnf config-manager --add-repo=file:///repo/appstream

  • This command points to a repository present in the local file system.

  • Structure of the URL indicates where the repository is found: file:///repo/appstream.

• Manual Creation of Repository File:

  • Create a file within /etc/yum.repos.d/ with the following structure:

  • Label: [repo_name]

  • name: Repository name

  • baseurl: Location of the repository

  • Must use three slashes (///) not two, and gpgcheck=0 to disable GPG checking.

Challenges of Exam Environment

• Potential exam challenge:

  • Information provided on how to access a repository server will most likely be from a locally installed server.

  • Generally, the URL to access the repository will be HTTP-based.

• Issues with Standalone Demo Environment:

  • Users will need to set up their own repository server in a disconnected environment.

  • The current demonstration focuses on configuring the installation disk as a repository.

Setting Up a Local Repository Server

• Check Disk Space:

  • Verify at least 10 GB in the root directory:

  • Use command: df -h

• Preferable procedure:

  • Reinstall the virtual machine on a 20 GB disk for optimal space.

• Clone Optical Disk:

  • Command: dd if=/dev/sr0 of=rel10.iso bs=1M

  • This copies the optical disk to an ISO file named rel10.iso.

  • If the message "no medium found" appears, ensure the optical disk device is connected (via VMware or other virtualization software).

• Mounting the ISO File:

  • Mount the created ISO file in the /repo directory:

  • Modify /etc/fstab to include:

    • rel10.iso /repo iso9660 defaults 0 0

  • Important to use double redirection to prevent overwriting the file.

• Use mount -a to mount everything that has not been previously mounted, which populates the /repo directory with necessary files.

Fallback Procedure if Less Space is Available

• If less than 10 GB is available:

  • Command: mknod /repo (create mount point)

  • Ensure /etc/fstab contains:

  • dev/sr0 /repo iso9660 defaults 0 0

  • Mount with: mount -a

• Caution with this approach due to potential disconnection issues with the optical disk. Better to ensure 10 GB availability.

Setting Up Repository Access for Client

• After setting up the repository server:

  • Command to configure the repository client:

  • dnf config-manager --add-repo=file:///repo/baseos

  • Edit repository files:

  • Open etc/yum.repos.d/repo_baseos.repo using Vim.

  • Set gpgcheck=0 to avoid signature verification errors.

• Repeat for the AppStream repository:

  • dnf config-manager --add-repo=file:///repo/appstream

  • Edit the respective .repo file to add gpgcheck=0.

Testing the Configuration

• Verify successful configuration by attempting to install a package:

  • Example command: dnf install m (where 'm' is a received package).

  • Check output on repository information and total download size.

  • Confirm installation was successful due to previously configured repository access.

Conclusion

• Following these steps allows successful configuration of repository access in a disconnected environment, critical for exam scenarios.