Linux basics [1d]

Resources

• Learn Enough Command Line to be Dangerous Show archive.org snapshot (it's in our library => Google Drive Show archive.org snapshot )
• CLI tricks every developer should know Show archive.org snapshot
• Install the tldr tool using sudo apt install tldr. You can then get usage examples for every console command, e.g. tldr ssh to get examples for the ssh command. (If there are no entries, run tldr -u and try again)

Exercises

Basic commands

Experiment and do something useful with the following commands. You might need to use tldr or Google the command.

• man (Get a more colorful output for man pages]
• top
• cat
• less
• dpkg -l
• apt-cache search <text>
• apt update
• apt dist-upgrade
• apt install <package-name>
• sudo <command>
• sudo su
• ssh
• scp
• df -h .
• du -h .
• ss --listening --tcp or (old) netstat --listen --tcp
• ln -s
• touch
• telnet
• curl
• ps
• kill
• kill -9
• pkill -f <partial-name>
• env
• dig
• grep (use with |)
• zgrep <needle> log/*.log*

Configuration files

Understand what you can do with the following configuration files:

• ~/.bashrc
• ~/.ssh/config
• ~/.gitconfig

Note that changes to your ~/.bashrc don't affect already opened shells.

Terminal editor

To edit files from within a terminal, you'll need a CLI editor.

• Chose an editor ( vim Show archive.org snapshot or nano Show archive.org snapshot )
  • If you chose vim, learn how to exit Show archive.org snapshot an open editor:
    • :q to exit
    • :wq to save (write) and exit
    • :q! to exit without writing
• Persist your choice in the $EDITOR Show archive.org snapshot variable. It defines the default for commands like git commit:

# Example with vim

# open the configuration file
vim ~/.bashrc

# navigate to the end of the file,
# press "i" to switch to insert mode
# then type out the line you want to add
export EDITOR=vim

# persist your changes
:wq

Note

While you could set $EDITOR locally to a graphical to a editor like gedit, this is not possible for remote shells to our servers.
Getting accustomed to a CLI editor will pay off in the long term.

Terminal shortcuts

Understand what the following shortcuts do in a terminal:

• Up-arrow
• Tab
• CTRL+R
• CTRL+Z / jobs / fg / bg Show archive.org snapshot
  • This allows you to faux-multitask within a single shell. E.g. you can temporarily suspend a running vim editor, take a look around the system, then return to your vim editor.

File ownership

Understand access rights and ownership of files:

• What does "ownership" mean for files?
• Each file has 9 flags, 3 read, 3 write, and 3 executable flags. What do they mean?
• Write a simple bash script that prints a message. How can you execute it?
• Write the same script in Ruby. What do you have to do to just call it from the command line without using the ruby command directly? Learn about the "shebang".