Linux Environment Variables: export, PATH, profile.d and systemd
Set Linux environment variables: export, echo, /etc/profile.d, ~/.bashrc, systemd Environment= and EnvironmentFile=, PATH, and debug with printenv.
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SSH config File on Linux: Host Aliases, Keys, Ports and ProxyJump
Use ~/.ssh/config on Linux: Host shortcuts, HostName, User, IdentityFile, Port, ProxyJump bastion, ssh -G test, and fix permissions…
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Linux Out of Memory (OOM): Find the Killer, Fix and Prevent Recurrence
Fix Linux out of memory: read OOM killer in dmesg/journalctl, use free and htop, systemd MemoryMax, swap as…
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systemd Service Failed to Start? Troubleshooting Guide for Linux
Fix systemd service failed to start: systemctl status, journalctl -u, ExecStart path and permissions, User=, dependencies, daemon-reload, and…
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Linux sudoers Explained: visudo, wheel Group and Safe NOPASSWD Rules
Understand /etc/sudoers on Linux: use visudo, sudoers.d drop-ins, wheel group, limit commands with Cmnd_Alias, audit auth logs, and…
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OpenSSL on Linux: Generate Private Keys, CSR and Self-Signed Certificates
Use OpenSSL on Linux to generate RSA/EC keys, create a CSR, issue a self-signed certificate for labs, set…
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Nginx 502 Bad Gateway: Causes and Fixes on Linux (Upstream, PHP-FPM, Timeouts)
Fix Nginx 502 Bad Gateway on Linux: check upstream is running, proxy_pass and fastcgi_pass, error.log messages, PHP-FPM pools,…
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How to Install and Use Git on Linux (Clone, Commit, Push and SSH Keys)
Install Git on Linux, configure user.name, clone repositories, branch, commit, push to GitHub/GitLab with SSH keys, and fix…
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How to Install Node.js and npm on Linux (LTS, nvm and Production Tips)
Install Node.js LTS on Linux with NodeSource or nvm, use npm correctly, run apps behind Nginx with systemd…
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MySQL vs MariaDB vs PostgreSQL: Which Database for Linux Servers?
Compare MySQL, MariaDB and PostgreSQL on Linux: compatibility, licensing, WordPress vs analytics workloads, backups, and when to pick…
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