Linux

1. 1

   The Shell and First Commands

   Welcome. If you have never used a terminal before, you are in the right place. A terminal is a window where you talk to your computer by typing...

   TerminalShellPromptFirst commandsMan pages
   20 min
2. 2

   Filesystem and Navigation

   In the last lesson you ran a handful of commands and read their output, but you never moved anywhere. Every command you typed happened in the same...

   Filesystem treeLsCdHidden filesAbsolute vs relative paths
   25 min
3. 3

   Files and Permissions

   You can now find your way around the filesystem, but so far you have only looked at files that were already there. Real work means creating files,...

   TouchCatCpMvRmMkdir+4
   30 min
4. 4

   Text Tools: grep, sed, awk

   Almost everything on a Linux system is text. Configuration files are text. Logs are text. The list of every user on the machine is a text file....

   GrepSedAwkHeadTailWc+2
   30 min
5. 5

   Pipes and Redirection

   In the last lesson you built small pipelines with | almost in passing, sending the output of one text tool into another. It is time to slow down and...

   PipesStdoutStderrStdinRedirectionTee
   25 min
6. 6

   Processes and Signals

   Type a command and press Enter, and something has to actually be running to carry it out. That something is a process, the operating system's word...

   PsTopHtopKillSignalsForeground+3
   30 min
7. 7

   Users and Groups

   Every command you have run so far, you ran as one particular account without ever being asked who you were. But Linux was built from day one to be...

   WhoamiIdSudo/etc/passwdUseraddAdduser+2
   25 min
8. 8

   Package Management

   Someone tells you to "just install htop". On Windows or a Mac you would go find a website, download an installer, click through it, and hope you got...

   AptDpkgApt searchApt showDnfPacman
   25 min
9. 9

   Networking Basics

   "The site is down." You open it and it works fine from your laptop but not from the server. Somewhere between the two machines, something is wrong,...

   Ip aIp routePortsSsCurlWget+4
   30 min
10. 10

    Shell Scripting

    You have worked out a sequence of six commands that does something useful: check a directory, make a folder, copy some files, print a summary. It...

    ShebangVariablesIfForWhileCommand substitution+2
    35 min
11. 11

    systemd Services

    You wrote a script that works. You run it, it does its job, and then you close your terminal and it dies with the session. You want it to start when...

    SystemctlUnit filesEnableStartStopStatus+1
    35 min
12. 12

    SSH and Remote Access

    The machine you actually need is somewhere else. It is a server in a data centre, a virtual machine in a cloud, a build box under someone's desk. You...

    SshSsh-keygenAuthorized_keysSsh-copy-idScpSsh config
    30 min
13. 13

    Logs and Journals

    A service that was working yesterday is not working now. Nobody changed anything, or so everybody says. You can stare at configuration files for an...

    /var/logSyslogJournaldJournalctlLog rotation
    25 min
14. 14

    Disks and Storage

    "No space left on device." The service stops writing, the database refuses connections, and everything downstream falls over, all because some...

    DfDuLsblkPartitionsFilesystemsMount+2
    30 min
15. 15

    Cron and Scheduled Tasks

    You wrote a backup script and it works beautifully, right up until the evening you forget to run it. Almost everything a server does routinely is...

    CrontabCron fields@daily@reboot/etc/cron.dailySystemd timers
    25 min
16. 16

    Performance and Monitoring

    Someone messages you: "the server feels slow." That is all you get. Slow could be a runaway process, memory exhaustion, a disk that cannot keep up,...

    UptimeLoad averageFreeVmstatIostatHtop+1
    30 min
17. 17

    Capstone: Server Setup

    Everything so far has been one idea at a time. Real work is never one idea at a time. Somebody hands you a bare Ubuntu machine and says "get the site...

    Sudo userSsh keysNginxSystemd timerBackupsJournalctl
    60 min

Every lesson, quiz, and tutor reply renders in your language. The AI tutor matches the language you ask in.

See how hiring teams interview engineers on Linux, in production-like environments.