Linux

linux Advanced

Build a custom Linux kernel module for hardware device monitoring

Learn how to write, build and load a custom Linux kernel module that exposes hardware metrics through a character device, proc and sysfs interfaces, then sign it for Secure Boot and package it with DKMS for distribution across kernel updates.

90 min 4 distros 20 views

linux Beginner

Check and manage running services on Linux with systemctl

Learn how to check running services on Linux, start, stop and restart them, enable them at boot, and read their logs with journalctl using systemctl on any systemd-based distro.

15 min 7 distros 73 views

linux Beginner

Fix Redis OOM command not allowed when used memory greater than maxmemory

Learn why Redis throws OOM command not allowed when used memory greater than maxmemory, how to diagnose it with redis-cli and free -m, and how to fix it by setting a sane maxmemory and eviction policy.

15 min 6 distros 71 views

linux Advanced

Build a highly available Linux cluster with Pacemaker and Corosync

Build a two-node active-passive cluster with Pacemaker, Corosync and pcs, including STONITH fencing, resource constraints and automatic failover of a floating virtual IP.

75 min 4 distros 91 views

linux Beginner

Find and view hidden files and directories on Linux

Learn how hidden files and dotfiles work on Linux, list them with ls -a and ls -la, find them with the find command, and view them in GUI and terminal file managers like ranger and mc.

15 min 7 distros 246 views

linux Beginner

Fix SSH Too many authentication failures error on Linux

Learn why SSH rejects you with too many authentication failures and how to fix it on the client with IdentitiesOnly and IdentityFile, manage ssh-agent keys correctly, and safely raise MaxAuthTries on servers you control.

15 min 7 distros 97 views

linux Beginner

Find out which process is using all your CPU or memory on Linux

Learn how to identify which process is consuming your Linux server's CPU or memory using top, ps aux, and sort, then safely terminate runaway or zombie processes without guessing.

15 min 7 distros 329 views

linux Beginner

Fix apt update E: Repository no longer has a Release file

Learn why apt update fails with the Release file error on Ubuntu and Debian, how to find the broken repository entry, and how to fix it safely, including EOL releases and GPG key issues.

15 min 4 distros 543 views

linux Beginner

Check disk space usage on Linux with df and du commands

Learn how to check disk space on Linux using df and du, find large files and directories, spot hidden disk usage from deleted but open files, and troubleshoot common out-of-space problems.

15 min 7 distros 291 views

linux Beginner

Find and kill processes using a specific port on Linux

Learn how to find which process is using a specific port on Linux, identify its owner safely, and kill it with the right tool. Covers lsof, ss, fuser, and how to prevent address already in use errors for good.

15 min 7 distros 371 views

linux Beginner

Fix PostgreSQL FATAL sorry, too many clients already

Learn why PostgreSQL throws FATAL: sorry, too many clients already, how to check and close idle connections, safely raise max_connections, and prevent the error from coming back with connection pooling.

20 min 4 distros 258 views

linux Intermediate

Implement backup rotation policies with automated cleanup using systemd timers and shell scripts

Set up automated backup rotation with systemd timers to manage storage space, implement retention policies for different backup types, and create monitoring alerts for backup health and cleanup processes.

45 min 4 distros 1,449 views