Linux Networking: ip, ping, traceroute and mtr (Troubleshooting Guide)
Troubleshoot Linux networking with ip addr/route, ping for reachability, traceroute for path hops, mtr for packet loss, and…
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Mount a Disk on Linux: Partition, ext4, mount and fstab (UUID)
Mount a new disk on Linux: lsblk, partition with fdisk, mkfs.ext4, mount, persist with /etc/fstab UUID and defaults,nofail,…
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SSH Connection Refused on Linux: Fix Port, sshd, Firewall and SELinux
Fix SSH connection refused: verify sshd is running and listening, correct Port in sshd_config, UFW/firewalld and cloud security…
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firewalld on Linux: Zones, Services, Ports and Permanent Rules (RHEL/Alma)
Configure firewalld on AlmaLinux/Rocky: install, zones, allow http/https/ssh, custom ports, --permanent rules, reload, and verify with firewall-cmd and…
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lsof Command on Linux: Find Process Using a Port or File
Use lsof on Linux: list open files and sockets, lsof -i :PORT, who blocks umount, deleted files still…
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No Space Left on Device on Linux: df, du, Logs, Docker and Inodes
Fix Linux no space left on device: df -h and df -i, du under /var, journalctl vacuum, large…
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dig and nslookup on Linux: DNS Troubleshooting (A, MX, TTL, resolvers)
Troubleshoot DNS on Linux with dig and nslookup: read resolv.conf, query A/MX records, +trace, test against 8.8.8.8, NXDOMAIN…
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Apache Virtual Host on Linux: ServerName, DocumentRoot and PHP-FPM
Create an Apache VirtualHost on Linux: install httpd/apache2, ServerName and DocumentRoot, enable site, PHP-FPM proxy, configtest, and fix…
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How to Install PHP on Linux (8.x, php-fpm, Extensions and Nginx)
Install PHP on Ubuntu and AlmaLinux/Rocky: php-fpm, common extensions for WordPress, version checks, Nginx fastcgi_pass, and disable phpinfo…
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How to Install Docker Compose on Linux (Compose v2 Plugin)
Install Docker Compose v2 on Linux as a docker compose plugin, write compose.yaml, docker compose up -d, logs,…
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