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Linux Upskill Challenge: Day 2

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Introduction

I’ve started following the Linux Upskill Challenge to sharpen my Linux knowledge and hands-on skills. It’s a series of 21 lessons designed to be completed daily, but I’ll be going through them at my own pace. I’ll share my journey and notes here as I move forward.

Day 2 - Basic navigation

RTFM

  • In this lesson, I learned a new acronym: RTFM – “Read the F***ing Manual.” 😆
  • When you’re learning and using Linux (or anything else) and have questions, of course, you’re always free to Google it or ask ChatGPT.
  • However, the best system administrators are those who first RTFM.

This is something we’re starting to forget nowadays!

  • Linux systems offer several ways to access documentation. But if—after searching—you still need help, you can always ask a well-written question in forums, Reddit, Discord, or other communities.

I think this is even more relevant today, especially when writing good prompts in the “GPT era.”

Looking for Documentation

  • The man command is a great place to start—most installed applications have their own manual.

  • For instance, you can find the manual for these commands:

    • man cp
    • man mv
    • man grep
    • man ls
    • even man man 🙂

  • That said, man output can be overwhelming for some commands or too minimal for others. That’s where tldr comes in—it provides simplified, community-written man pages for common Linux (and other OS) commands.

  • tldr is another tool for viewing documentation. I installed it using sudo apt install tldr, but it didn’t work right away on my EC2 instance.
  • I got the following error:
tldr: /home/ubuntu/.local/share/tldr: createDirectory: does not exist (No such file or directory)
  • I fixed it with these two commands:
mkdir -p ~/.local/share/tldr
tldr --update
  • The second command pulls the latest pages from the official GitHub repo (make sure your server has internet access!).
  • I tried tldr with the same commands as before, and yes—it showed me much more simplified info.
  • I also learned about the apropos command, which is equivalent to man -k.
  • Both are useful when you kind of know what a command does and want to search for keywords in the manual.
  • For example, if you search for the phrase “remove file” using apropos "remove file", you’ll get results like this:
ubuntu@ip-172-31-92-220:~$ apropos "remove file"
git-rm (1)           - Remove files from the working tree and from the index
rm (1)               - remove files or directories
ubuntu@ip-172-31-92-220:~$ man -k "remove file"
git-rm (1)           - Remove files from the working tree and from the index
rm (1)               - remove files or directories

  • Some commands—especially shell built-ins—don’t have man pages.

  • For those, you can use the help command instead.

  • Example: use help export instead of man export.

  • I found exceptions like echo, which works with both man echo and help echo.

  • The best way to check if a command is a shell built-in is to use the type command.

  • Lastly, there’s the info command. It gives more detailed documentation, sometimes written in a tutorial style and with hypertext navigation.

  • I discovered a command that gives you documentation about the Linux file system: man hier.

  • / is the top-level directory (called root) for all other folders.

  • 🧭 To find out where you are in the file system, use pwd—this is like your GPS in Linux. 🛰

  • By default, you’ll start in the /home/<user> directory, unless you’re logged in as root, in which case you’ll be in /root.

  • You can move between directories using cd:

    • cd .. takes you “up” one level.
      • cd . keeps you in the same folder. đŸ€”

  • You can use either relative or absolute paths to move around:

    • For example, if you first do cd /var, then both cd log and cd /var/log will get you to the same place.

  • Just running cd returns you to your home directory, as does cd ~.

  • You can also use ~ as a shortcut to move into folders inside your home directory from anywhere.

    • For instance, if you’re in /var/log and want to go to /home/ubuntu/data/example, just use cd ~/data/example.
ubuntu@ip-172-31-92-220:/var/log$ cd ~/data/example/
ubuntu@ip-172-31-92-220:~/data/example$

Listing Files in a Folder

  • I used ls with different options (“switches”) to list files.
    For example: ls, ls -l -L, and ls -l -t -r -a (or just ls -ltra).

  • Files or folders that start with a . are hidden. Use ls -a to see them.

  • You can combine switches and provide a folder path:
    e.g., ls -ltra /var/log

  • Entries that start with d are directories.

  • Some terminals show these in a different color—if not, try --color=auto.

ubuntu@ip-172-31-92-220:~/data/example$ ls -ltra /var/log
...

Basic Directory Manipulation

  • I created a new folder with mkdir test, then moved into it with cd test.
  • You can repeat this to build nested folder structures.
mkdir test
cd test
  • To move a folder into another directory, I used mv:
  • Created a folder test2, then moved example from test to test2.
mv test/example test2
  • To remove an empty directory, use rmdir.
  • To remove a non-empty one, use rm -r.

Basic File Manipulation

  • To create a new (empty) file: touch newfile.txt
  • To move it: mv newfile.txt test2
  • To delete it: rm
touch newfile.txt
mv newfile.txt test2
rm test2/newfile.txt

A Bit More Advanced Directory Navigation (Stack-Based)

  • I learned about pushd and popd, which let you move between folders using a stack (LIFO order).
  • It’s different from cd ..—with pushd you can hop to /etc, then /var/log, and then jump back in reverse order using popd.
  • Use dirs to see the current directory stack.
pushd /etc
pushd /var/log
dirs
popd
popd
  • If you run pushd without arguments, it swaps your current and previous directories—similar to cd -, but it remembers your path history.

So these are my notes for the Day 2 – Basic Navigation of the Linux Upskill Challenge.

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