linuxexpert-practice-labs/labs/lfcs/1-4-software-packages/README.md

LFCS 1.4: Software packages

Finding which package has a command, adding a third-party repository, verifying installed files, and holding a package at its version.

Before you start

The VM needs internet access. The lab makes sure dig isn't installed, and changes one character in a configuration file of the openssh-server package (a comment, so sshd keeps working). On Ubuntu, removing dig also removes the ubuntu-standard metapackage; reset puts both back.

Tasks

1. Find which package provides the dig command, install it, and list the package's files. Write the package's name to /root/lab-answers/1.
2. Add a third-party repository with its signing key (Docker's or another vendor's published instructions are good practice), install a package from it, then remove the repository so it's no longer used. Write the package's name to /root/lab-answers/2.
3. Find the changed file with the package manager, write its full path to /root/lab-answers/3, and restore the packaged file. rpm -V openssh-server or dpkg --verify openssh-server lists the file until it's restored.
4. Stop the package curl from being upgraded.

Hints

• dnf provides, rpm -qf, rpm -ql; apt-file search, dpkg -S, dpkg -L.
• A .repo file in /etc/yum.repos.d/, or a .sources file in /etc/apt/sources.list.d/ with a key in /etc/apt/keyrings/; dnf repolist, apt-cache policy.
• rpm -V, dpkg --verify; delete the file, then dnf reinstall or apt install --reinstall -o Dpkg::Options::=--force-confmiss.
• dnf versionlock (from python3-dnf-plugin-versionlock), apt-mark hold.