Linux guides
Hands-on guides that cover Linux. Every command is run and verified on a live server before it is published.
GuideWhat Is a Process
Every command on your server becomes a process with a PID, an owner and a parent. List the linux processes you own on Ubuntu and read each column.
GuideUsers and Groups
Linux users and groups decide who owns every file and process. Create a service account and a team group on a live server, then read what an account holds.
GuideThe Shell and Your First Commands
Learn Linux command line basics on a live Ubuntu 24.04 server. Run whoami, pwd, uname and id to see who you are and where you are before you change anything.
GuideDisks and Partitions
Map the linux disks on an Ubuntu 24.04 server: run lsblk to list the disk and its partitions, then df to see how much space is left.
GuideInterfaces and the ip Command
Use the linux ip command on an Ubuntu 24.04 server to see an interface, its IP address, and the route your traffic takes to leave the machine.
GuideThe First Hour
The eight things to do in the first hour on a new Linux server, before scanners find it. A practical hardening guide, with every command tested on a real VPS.
GuideSignals and Killing Processes
You do not close a program on a server, you signal it. Learn the linux kill signals, the polite TERM and the forceful KILL, and stop a stuck process cleanly.
GuideNavigating the Filesystem
Linux filesystem navigation with cd, ls and pwd on an Ubuntu 24.04 server. Move around the directory tree and learn to read what ls -la is telling you.
GuideOwnership: chown and chgrp
Linux file ownership with chown sets which user and group a file belongs to. Change ownership on a live server and see why a service needs the right owner.
GuidePorts and Sockets With ss
Use the linux ss command to see which ports are open on a server, which process owns each one, and whether it listens to the world or just localhost.
GuideFilesystems, Mounts and fstab
Learn linux mount and fstab on Ubuntu 24.04: how mount attaches a partition to a directory, findmnt shows what is mounted, and fstab makes it stick.
GuideRead, Write and Execute Permissions
Linux file permissions rwx are the ten characters at the start of every ls -l line. Read them for user, group and other, and learn what execute means.
GuideJobs, Foreground and Background
One terminal can run more than one thing. Push a command into the background, list your linux background jobs, and bring one back with fg when you need it.
GuideDisk Usage: df and du
Master linux disk usage with df and du on Ubuntu 24.04: df shows free space per filesystem, du shows what fills a directory so you find the culprit.
GuideWorking With Files and Directories
Create and move files on Linux with mkdir, cp, mv and rm. Practise on a real project tree so copying a config or cleaning up a release becomes muscle memory.
GuideDNS Resolution
Understand linux dns resolution: how a name becomes an IP address on Ubuntu, how to query a name with resolvectl, and how to read where the answer came from.
Guidedpkg and .deb Files
The dpkg command Linux runs under apt: list an installed package, see the files it placed, and map a file back to its package.
Guidechmod: Symbolic and Octal
The chmod command Linux uses edits permission bits two ways. Add execute to a script with symbolic mode, then lock a secrets file to 640 with octal mode.
Guidesystemd Services Explained
Server software runs as a service that starts on boot and restarts on failure. Meet systemd, the service manager on every Linux box, and read a live status.
GuideViewing and Editing Files
View files on the Linux command line with cat, less, head and tail. Read configs and logs, and watch a log grow in real time while a problem is happening.
Guidetar and Compression
Learn linux tar and compression on Ubuntu 24.04: use tar to bundle a directory into one archive, gzip to shrink it, then list and extract it.
GuideText Processing With sed
Use the linux sed command on Ubuntu 24.04 to find and replace text as it streams past, editing a log from a script without opening an editor.
Guidesudo and the Root Account
Linux sudo and root explained: why you never log in as root, how sudo runs one command at a time, and how group membership decides who may use it.
GuideWildcards and Globbing
Linux wildcards and globbing explained: how the shell expands star, question mark, brackets and braces before a command runs, so you act on many files at once.
GuideText Processing With awk
Use the linux awk command on Ubuntu 24.04 to read text as columns: pull specific fields from a log or CSV and add them up into the numbers you need.
GuideRedirection and Pipes
Linux pipes and redirection explained. Send command output to a file and chain small tools together to answer real questions about your logs in one line.
GuideSSH Keys and Passwordless Login
SSH key authentication Linux servers support beats passwords. Generate a key pair, learn the private and public split, and set up passwordless login.
GuideBuilding From Source
Build from source on Linux when no package exists: fetch the code, then run configure, make, and make install to get a working binary.
GuideFinding Files and Text
Find files and search text on Linux with find and grep. Locate files by name, type and age, then search inside them for the one error line that matters.
GuideScheduling With cron
Some jobs run on a schedule, not on demand. Write your first crontab entry, read the five time fields, and schedule linux cron jobs on a live Ubuntu server.
Guidecut, sort, uniq and tr
Combine linux cut, sort and uniq in a pipe on Ubuntu 24.04 to count how often each value appears in a file, the pattern behind many one-liners.
Guideumask and Default Permissions
The Linux umask default permissions rule sets the mode of every new file. See how umask subtracts bits, and tighten it so new files are not group-writable.
GuideThe Environment and PATH
Understand the Linux PATH and environment variables: why a command just works, why it sometimes says command not found, and what every process inherits.
GuideAccess Control Lists
Linux access control lists (ACL) grant one user access the owner-group-other model cannot. Add a rule with setfacl and read it back with getfacl.
GuideAccount and Password Policy
Set a Linux password policy with chage: read password ageing, set a maximum age, and lock an account cleanly when someone leaves the team.
GuideResource Limits: nice and ulimit
One heavy process should not starve the server. Lower a job's priority with linux nice, and read the per-shell caps that ulimit enforces on every process.
GuideDiagnosing a Slow Connection
Linux network troubleshooting for a slow service: test the layers in order, network, then DNS, then the application, and stop at the first that fails.
GuideScheduling an Automated Backup
Write a linux backup script and a cron entry on Ubuntu 24.04 so a directory is archived every night on its own, tying the whole series together.