Lab1 Introduction to UNIX

During this week we will play-through the exercises refreshing your UNIX knowledge. Starting from the next week we start building the real serve-side service infrastructure. Therefore we find it critical for you to feel fluent with command line interface (CLI) of UNIX. The outline of this lab is as follows:

• CLI Intro
• Trying out basics of bash shell
• Solving bash shell exercises
• Playing bash games

CLI Intro

Command line interface interaction can be reduced to: typing in the desired command and reading or interpreting the corresponding output.

• Examples (assuming bash shell syntax, and GNU/Linux standard commands):
  • creating a directory:
    • mkdir dir1
  • listing the files in a directory:
    • ls dir1
  • renaming the directory:
    • mv dir1 dir2
  • copying a file
    • cp file1.txt dir2/file1.txt
  • navigating to the dir1
    • cd dir1
  • navigating one level up in the directory tree
    • cd ..
  • discovering the current directory (or current write directory (CWD))
    • pwd
  • removing a file
    • rm file1.txt
  • removing all text files (by *.txt extension)
    • rm *.txt
  • recursively removing all files in the current directory
    • rm -rf *
• There many more commands we face during this lab (here we showed just few file management ones)

As you can see, using the command line is not always trivial, nor is it safe. The last command actually tries to delete all the files in current directory, without really asking you whether it should. This is why one should have a proper grasp of commands and techniques used to manipulate a UNIX/Linux system.

Sandbox

To prevent accidents, we will first go into a "sandbox" machine.

Moving from one host to another on Linux systems is usually done by utilizing a protocol called SSH (Secure Shell). This can be used to login into another machine.

  The syntax usually follows like this: ssh <username>@<hostname>
  Example: mouse@lab.cs.ut.ee

Let's log into a machine called "lab.cs.ut.ee" with our university users. For Linux/Mac users this task is easy (classroom computers have Linux installed) - open terminal, and insert the previous command. Windows people will need to find out a solution for themselves. Common tool is called "putty".

You need to be able inside the University network to log in into that machine. University VPN helps if you're not in class.

Bash introduction

Helpful materials

At first, writing up commands that you won't remember is a very good idea. We will never prevent you from being able to look at your notes, even during exam!

This means that if you want, you can make a cheat sheet, or just write up any commands that you think you will not be able to remember.

In case you need more details about particular shell usage you may refer to:

• Shell Commands Explainer
• Bash Guide for Beginners
  • This one slightly larger but also detailed document about the bash shell usage
  • Recommended as a reference! When solving exercises you may quickly find the chapter to read through as the resource is having well organized index.

Intermediate tasks

If you want to learn by playing:

  Game called "bashcrawl", for beginner Linux users:

    Idea of the game: Crawl through a dungeon of bash.
    How to get started:

    (On our lab.cs.ut.ee machine, in your home directory)
    git clone https://gitlab.com/slackermedia/bashcrawl.git
    cd bashcrawl/entrance
    cat scroll
    (continue using the instructions)

  Game called "Command Line Heroes", for those who want to solidify their knowledge of command line.

    Idea of the game: Try to write as many Linux commands as possible in limited time.
    How to get started:

    Go to https://www.redhat.com/en/command-line-heroes/bash/index.html in your computer's browser

  Game that teaches how to write Bash scripts:

    https://www.hackerrank.com/domains/shell?filters%5Bsubdomains%5D%5B%5D=bash