Linux 101⚓︎
Difficulty:
Direct link: Linux 101 terminal
Objective⚓︎
Request
Visit Ginger Breddie in Santa's Shack on Christmas Island to help him with some basic Linux tasks. It's in the southwest corner of Frosty's Beach.
Ginger Breddie @ Santa's Surf Shack
Hey, welcome to Santa's Surf Shack on tropical Christmas Island! I'm just hanging ten here, taking it easy while brushing up on my Linux skills.
You ever tried getting into Linux? It's a super cool way to play around with computers.
Can you believe ChatNPT suggested this trip to the Geese Islands this year? I'm so thrilled!
Kudos to ChatNPT, eh? The sunshine, the waves, and my surfboard – simply loving it!
So, what do you have planned? Care to join me in a Linux session?
Solution⚓︎
Welcome message
The North Pole 🎁 Present Maker:
All the presents on this system have been stolen by trolls. Capture trolls by following instructions here and 🎁's will appear in the green bar below. Run the command "hintme" to receive a hint.
Question 1⚓︎
Question
Perform a directory listing of your home directory to find a troll and retrieve a present!
To list directories in Linux, it's simply ls.
Answer
ls
Question 2⚓︎
Question
Now find the troll inside the troll.
To find the troll, simply read the troll file with cat.
Answer
cat troll_19315479765589239
Question 3⚓︎
Question
Great, now remove the troll in your home directory.
To remove file, run rm on it.
Answer
rm troll_19315479765589239
Question 4⚓︎
Question
Print the present working directory using a command.
To get the current working directory, run pwd.
Answer
pwd
Question 5⚓︎
Question
Good job but it looks like another troll hid itself in your home directory. Find the hidden troll!
To list hidden files/folders, use ls -a which will list ALL files/folders. -l switch makes it look nicer but not required.
Answer
ls -a
Question 6⚓︎
Question
Excellent, now find the troll in your command history.
Run history to get history of commands and pipe its output to input of grep which will search for -i (case-insensitive) word troll.
Answer
history | grep -i troll
Question 7⚓︎
Question
Find the troll in your environment variables.
Command env outputs all environment variables for the current user - pipe its output to grep to find the troll.
Answer
env | grep -i troll
Question 8⚓︎
Question
Next, head into the workshop.
Simply cd to change directory
Answer
cd workshop
Question 9⚓︎
Question
A troll is hiding in one of the workshop toolboxes. Use "grep" while ignoring case to find which toolbox the troll is in.
Run grep -i troll * to read all files in current directory, searching for the case-insensitive word troll.
Answer
grep -i troll *
Question 10⚓︎
Question
A troll is blocking the present_engine from starting. Run the present_engine binary to retrieve this troll.
First, we need to find the present_engine file using find / -name present_engine 2>/dev/null which looks for all files with this name while dropping all error messages for cleaner output (stderr in this case is lack of permissions for some files/directories).
Once the file is found in the current directory, it cannot be ran (permission denied) - this is due to missing execution bit.
Set the execution bit using chmod +x and rerun the file FTW.
Answer
find / -name present_engine 2>/dev/null
chmod +x /home/elf/workshop/present_engine
/home/elf/workshop/present_engine
Question 11⚓︎
Question
Trolls have blown the fuses in /home/elf/workshop/electrical. cd into electrical and rename blown_fuse0 to fuse0.
To rename files, use mv .
Answer
cd /home/elf/workshop/electrical
mv blown_fuse0 fuse0
Question 12⚓︎
Question
Now, make a symbolic link (symlink) named fuse1 that points to fuse0
Use ln -s to create a symbolic link - source filename is first while destination is next.
Answer
ln -s fuse0 fuse1
Question 13⚓︎
Question
Make a copy of fuse1 named fuse2.
To copy, use cp.
Answer
cp fuse1 fuse2
Question 14⚓︎
Question
We need to make sure trolls don't come back. Add the characters "TROLL_REPELLENT" into the file fuse2.
Use echo to output text, appending (>>) it to the file.
Answer
echo "TROLL_REPELLENT" >> fuse2
Question 15⚓︎
Question
Find the troll somewhere in /opt/troll_den.
Since challenge mentions "somewhere," we can use case-insensitive -iname switch for the find command, as well as wildcards (*) to include filenames that contain troll in their filename.
Answer
find /opt/troll_den -iname troll
Question 16⚓︎
Question
Find the file somewhere in /opt/troll_den that is owned by the user troll.
To find a file based on owner, use -user switch.
Answer
find /opt/troll_den -user troll 2>/dev/null
Question 17⚓︎
Question
Find the file created by trolls that is greater than 108 kilobytes and less than 110 kilobytes located somewhere in /opt/troll_den.
Find a file (-type f) that is over 108KB (-size +108k) but less than 110KB (-size -110k).
Answer
find /opt/troll_den -type f -size +108k -size -110k
Question 18⚓︎
Question
List running processes to find another troll.
top can be used to monitor running processes.
Answer
top
Question 19⚓︎
Question
The 14516_troll process is listening on a TCP port. Use a command to have the only listening port display to the screen.
To get listening processes use netstat with -ntlp switches to not resolve names, TCP-only, listening, and programs/PID respectfully.
Answer
netstat -ntlp
Question 20⚓︎
Question
The service listening on port 54321 is an HTTP server. Interact with this server to retrieve the last troll.
Since this is an HTTP server, curl can be used to make a basic request to the localhost on specified port.
Answer
curl http://127.0.0.1:54321
Question 21⚓︎
Question
Your final task is to stop the 14516_troll process to collect the remaining presents.
To list all running processes, ps -aux can be used and from there, use kill to kill the process PID in question.
Answer
kill 28128
Challenge Completed!
Response⚓︎
Ginger Breddie @ Santa's Surf Shack
Wow, if your surfing skills are as good as your Linux skills, you could be winning competitions!
Right on GB. 🤙 Off to explore the rest of Christmas Island...