Omer Cakmak

Learn how to restart the cron or crond service on Ubuntu, Debian, RHEL, Rocky Linux, AlmaLinux and CentOS, when a restart is required, and why crontab changes normally reload automatically.

Install Java on RHEL, Rocky Linux, AlmaLinux, CentOS Stream, Oracle Linux, or Fedora using OpenJDK, Eclipse Temurin, or Oracle JDK, then configure alternatives, JAVA_HOME, updates, verification, and uninstall.

Install JasperReports Server on RHEL, Rocky Linux, AlmaLinux, CentOS Stream, Oracle Linux, or Fedora using the evaluation binary installer with bundled components or a production WAR deployment on supported Tomcat and …

Compare DNF4 and DNF5 command differences, plugins, history syntax, and group handling, and learn what to change in scripts before your distribution moves to DNF5.

List users in Linux with getent, /etc/passwd, who, and id. Filter normal and system accounts, see logged-in sessions, and check whether a user exists on Ubuntu and RHEL.

List groups in Linux with getent, groups, id, and /etc/group. Check user group membership, list group members, and compare primary vs supplementary groups.

Install Node.js on Ubuntu with apt nodejs, NodeSource setup scripts, NVM for multiple versions, or the official nodejs.org linux-x64 tar.xz under /opt, verify with node --version and npm --version, and uninstall per …

sort reads lines from files or stdin and prints them in order. Use it for log lines, CSV columns, version strings, and pipeline output from ls, awk, or find — then pair with uniq to drop duplicates.

rmmod removes loadable kernel modules from a running Linux kernel. Use it to unload drivers you loaded for testing; modprobe -r is the higher-level alternative that handles dependencies.

List obsolete packages on Ubuntu with apt list ?obsolete, preview removal with apt-get -s, purge safely after do-release-upgrade, and distinguish obsolete packages from autoremove and rc config cleanup.

Downgrade Ubuntu 21.04 (Hirsute Hippo) to 20.04 LTS (Focal Fossa) with apt pinning, sources.list retargeting, and aptitude dist-upgrade—no data loss under /home when the run completes, plus dpkg recovery, reboot checks, …

Install AWS CLI on Debian 11, 12, or 13 with the official awscli-exe-linux bundle, apt install awscli on Trixie, or legacy pip awscli. Verify with aws --version, configure credentials, fix PATH conflicts, and uninstall …

Install Flatpak on Debian 11, 12, or 13 with apt install flatpak, add the Flathub remote, install sandboxed apps with flatpak install, update with flatpak update, and remove Flatpak cleanly from system or user scope.

Install Go on Debian 11, 12, or 13 with apt install golang-go, the official go.dev Linux tarball under /usr/local/go, PATH and GOPATH setup, go mod init, verify with go version, and uninstall without mixing two …

Install ifconfig on Debian 11, 12, or 13 with apt install net-tools, fix ifconfig command not found on minimal images, compare with ip from iproute2, verify interfaces, and uninstall net-tools cleanly.

Install netstat on Debian 11, 12, or 13 with apt install net-tools, fix netstat command not found on minimal images, compare listening ports and routes with ss from iproute2, and remove net-tools cleanly.

Install PostgreSQL on Debian 11, 12, or 13 with apt install postgresql, verify systemd and psql, create users and databases, add the PGDG repository for other majors, and remove clusters cleanly with pg_dropcluster.

Install curl on Debian 11, 12, or 13 with sudo apt install curl, verify with curl --version and an HTTPS request, fix curl command not found and libcurl4t64 dependency errors, install php-curl when PHP needs libcurl, and …

Install Java on Debian 11, 12, or 13 with apt install openjdk-21-jdk or openjdk-25-jdk, default-jdk metapackages, Eclipse Temurin from Adoptium, and update-java-alternatives. Set JAVA_HOME, verify java -version, compile …

Install Wine on Debian 11, 12, or 13 with apt install wine and i386 multiarch, add the WineHQ repository for winehq-stable or staging, initialize a WINEPREFIX with wineboot, use winetricks for runtimes, and uninstall …

Install Firefox on Debian 11, 12, or 13 with firefox-esr from Debian, the official Mozilla APT repository for the latest release, Snap, Flatpak, or a .tar.xz from firefox.com. Verify versions, set the default browser, …

Install the latest Python on Debian 11, 12, or 13 without breaking system python3: use apt for the distro version, uv or pyenv for upstream releases, or make altinstall from python.org. Create a venv, verify with python …

Install sudo on Debian 11, 12, or 13 with apt install sudo, add your user to the sudo group, verify with sudo -l, and edit sudoers safely with visudo. Covers minimal installs without sudo, su as root, and fixing common …

Install Eclipse Temurin on Debian 11, 12, or 13 with the Adoptium APT repository, a manual .tar.gz under /opt, or update-alternatives. Switch JDKs with update-java-alternatives, set JAVA_HOME, verify with java -version, …

Install Git on Debian 11, 12, or 13 with sudo apt install git, optionally pull a newer release from backports or build from the official kernel.org tarball, set user.name and user.email, verify with git --version, update …

Install Node.js on Debian 11, 12, or 13 with apt install nodejs npm, switch versions with nvm, or unpack official nodejs.org Linux binaries. Configure npm, create a package.json project, run scripts with node and npx, …

Install Steam on Debian 11, 12, or 13 with steam-installer from contrib, Valve steam_latest.deb or repo.steampowered.com APT repo, Snap, or Flathub. Enable i386 multiarch, install steam-devices for controllers, bootstrap …

Install Google Chrome on Debian 11, 12, or 13 amd64 with the official google-chrome-stable_current_amd64.deb or Google signed APT repository, verify with google-chrome --version, set the default browser, update through …

List installed packages on Debian with apt list --installed, dpkg -l, dpkg-query, and apt-mark showmanual. Search one package, count totals, list Snap and Flatpak apps, export names for another machine, and read apt or …

Install eza on Debian 11, 12, or 13 with apt install eza, the deb.gierens.de APT repository for newer releases, or cargo install eza with rustup. Verify with eza --version, set ls aliases, use tree and Git listings, and …