Calcolatori Elettronici (a.y. 2017-2018) - Hands-on Linux

1. Getting access to a Linux machine

1.1 A Zero footprint Linux shell

You can start playing with a Linux shell straight away by using JSLinux. No installation on your machine is needed. A Linux shell (albeit limited in functionality) is made avalable in your browser.

1.2 Accessing a remote Linux host via SSH

Prerequisite: SSH client installed on your machine. SSH is pre-installed in most Linux distributions or it can easily installed via the apt command. SSH client for Windows are available here and here.

If you have a Linux machine, then you can establish a SSH session by issuing the the following command on a terminal:

> ssh -p 2220 -l bandit0 bandit.labs.overthewire.org

where bandit.labs.overthewire.org is the address of the remote host, -p 2220 specified the port, and -l bandit0 specifies the account on the host. (The password for bandit0 on bandit.labs.overthewire.org is … bandit0).

1.3 Installing a Linux distribution on your machine

You can create a local, disposable copy of Linux by using the virtualization technology. Many virtualization solutions are available today, the most prominent being VMware and VirtualBox.

1.4 Linux on MacOS

Just open a terminal.

1.5 Linux on Window 11

See Installare Linux in Windows con WSL (in Italian) or Install Ubuntu on WSL2 on Windows 10 (in English).

2. Basic Linux shell commands

Learn to use and play with the following commands:

• pwd - Print name of current working directory
• cd - Change directory
• ls - List directory contents
• file - Determine file type
• less - View file contents
• cp - Copy files and directories
• mv - Move/rename files and directories
• mkdir - Create directories
• rm - Remove files and directories
• which - Display which executable program will be executed
• man - Display a command’s manual page
• whatis - Display a very brief description of a command
• cat - Concatenate files
• sort - Sort lines of text
• uniq - Report or omit repeated lines
• grep - Print lines matching a pattern
• find - Find…
• wc - Print newline, word, and byte counts for each file
• head - Output the first part of a file
• tail - Output the last part of a file
• tee - Read from standard input and write to standard output and files

3. Play with Bandit

Improve your hands-on skills by taking on the Bandit challenges.

4. Advanced Linux shell commands

• Standard Input, Output, And Error
• I/O Redirection
  • Redirecting Standard Output
    • ls -l /usr/bin > ls-output.txt
    • ls -l /usr/bin >> ls-output.txt
  • Redirecting Standard Error
    • ls -l /bin/usr > ls-output.txt
    • ls -l /bin/usr 2> ls-error.txt
  • Redirecting Standard Output And Standard Error To One File
    • ls -l /bin/usr > ls-output.txt 2>&1
    • ls -l /bin/usr &> ls-output.txt
    • ls -l /bin/usr &>> ls-output.txt
  • Disposing Of Unwanted Output
    • ls -l /bin/usr 2> /dev/null
  • Redirecting Standard Output and Standard Input

    • wget https://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Alan_Turing_Aged_16.jpg/440px-Alan_Turing_Aged_16.jpg
      ls -la 440px-Alan_Turing_Aged_16.jpg
      split --bytes=10000 440px-Alan_Turing_Aged_16.jpg
      ls -la x*
      cat x?? > new-440px-Alan_Turing_Aged_16.jpg
      diff 440px-Alan_Turing_Aged_16.jpg new-440px-Alan_Turing_Aged_16.jpg 
      

    • cat ls-output.txt
      cat
      cat > readme.txt
      cat < readme.txt
      

• Pipes
  • Filters
    • ls /bin /usr/bin | sort | less
  • Read From Stdin And Output To Stdout And Files
    • ls /usr/bin | tee ls.txt | grep zip