Scenario: "Saint John": what is writing to this log file?
Level: Easy
Type: Fix
Access: Public
Description: A developer created a testing program that is continuously writing to a log file /var/log/bad.log and filling up disk. You can check for example with tail -f /var/log/bad.log. This program is no longer needed. Find it and terminate it. Do not delete the log file.
Test: The log file size doesn't change (within a time interval bigger than the rate of change of the log file).
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: There's a web server access log file at /home/admin/access.log. The file consists of one line per HTTP request, with the requester's IP address at the beginning of each line.
Find what's the IP address that has the most requests in this file (there's no tie; the IP is unique). Write the solution into a file /home/admin/highestip.txt. For example, if your solution is "1.2.3.4", you can do echo "1.2.3.4" > /home/admin/highestip.txt
Test: The SHA1 checksum of the IP address sha1sum /home/admin/highestip.txt is 6ef426c40652babc0d081d438b9f353709008e93 (just a way to verify the solution without giving it away.)
Description: There is a web server on port :80 protected with Port Knocking. Find the one "knock" needed (sending a SYN to a single port, not a sequence) so you can curl localhost.
Test: Executing curl localhost returns a message with md5sum fe474f8e1c29e9f412ed3b726369ab65. (Note: the resulting md5sum includes the new line terminator: echo $(curl localhost))
Scenario: "Resumable Server": Linux Upskill Challenge
Level: Easy
Type: Do
Access: Email
Description: This is a Debian 11 server without a challenge; it's for you to do as you please.
It's meant in principle for guided tutorials like the Linux Upskill Challenge, with some limitations (there's still no outgoing Internet access).
Once you are done with your task, you can stop (pause) your server from your dashboard.
From the dashboard at any time you can restart the stopped server to continue your tasks or you can stop the server if it's running. You can also destroy it at any time.
After 30 mins, the server will be stopped. You can restart it from the dashboard.
This is a "beta" feature and there can be some issues.
Description: There's a file /home/admin/scores.txt with two columns (the first number is a line number and the second one is a test score for example).
Find the average (more precisely; the arithmetic mean: sum of numbers divided by how many numbers are there) of the numbers in the second column (find the average score).
Use exactly two digits to the right of the decimal point. i. e., use exaclty two "decimal digits" without any rounding. Eg: if average = 21.349 , the solution is 21.34. If average = 33.1 , the solution is 33.10.
Save the solution in the /home/admin/solution file, for example: echo "123.45" > ~/solution
Tip: There's bc, Python3, Golang and sqlite3 installed in this VM.
Description: A web application relies on the PostgreSQL 13 database present on this server. However, the connection to the database is not working. Your task is to identify and resolve the issue causing this connection failure. The application connects to a database named app1 with the user app1user and the password app1user.
Description: There's a Kubernetes Deployment with an Nginx pod and a Load Balancer declared in the manifest.yml file. The pod is not coming up. Fix it so that you can access the Nginx container through the Load Balancer.
There's no "sudo" (root) access.
Test: Running curl 10.43.216.196 returns the default Nginx Welcome page.
See /home/admin/agent/check.sh for the test that "Check My Solution" runs.
Description: In a directory /home/admin/data, there are multiple files, all of them with same content. One of these files has been modified, a word was added. You need to identify which word it is and put it in the solution file (both newline terminated or not are accepted).
Test:md5sum /home/admin/solution should return 55aba155290288b58e9b778c8f616560 or 2eeefea9fc4b16ea624bed5c67a49d80
Check My Solution: The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can
Description: The directory at /home/admin/git has a Git repository with a Golang program and a test for it.
To execute the test, from this "git" directory run: go test. The last (current HEAD) commit fails the test. Suppose the first commit passed the test.
Find the (long hash) commit that first broke the test and enter it in the /home/admin/solution file. For example: echo 9e80a7eb1b09385e93ab4a76cb2c93beec48fd9f > /home/admin/solution
Description: Break the Comma Separated Valued (CSV) file data.csv in the /home/admin/ directory into exactly 10 smaller files of about the same size named data-00.csv, data-01.csv, ... , data-09.csv files in the same directory. All the files should have the same header (first line with column names) as data.csv. None of the smaller files should be bigger than 32KB.
Note: to simplify, disregard broken lines in your files (ie, you can break a file at any point, not just at a newline). The resulting files don't have to be proper CSV files.
Test: The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: Join (merge) all the 338 files in /home/admin/polldayregistrations_enregistjourduscrutin?????.csv into one single /home/admin/all.csv file with the contents of all the CSV files in any order. There should be only one line with the names of the columns as a header.
Test: The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A spy has left a password in a file in /proc/sys . The contents of the file start with "secret:" (without the quotes).
Find the file and save the word after "secret:" to the file /home/admin/secret.txt with a newline at the end (e.g. if the file contents were "secret:password" do: echo "password" > /home/admin/secret.txt).
(Note there's no root/sudo access in this scenario).
Description: There's an Nginx web server running on this machine, configured to serve a simple "Hello, World!" page over HTTPS. However, the SSL certificate is expired.
Create a new SSL certificate for the Nginx web server with the same Issuer and Subject (same domain and company information).
Test: Certificate should not be expired: echo | openssl s_client -connect localhost:443 2>/dev/null | openssl x509 -noout -dates and the subject of the certificate should be the same as the original one: echo | openssl s_client -connect localhost:443 2>/dev/null | openssl x509 -noout -subject
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute
Scenario: "Tokamachi": Troubleshooting a Named Pipe
Level: Easy
Type: Fix
Access: Email
Description: There's a process reading from the named pipe /home/admin/namedpipe.
If you run this command that writes to that pipe:
/bin/bash -c 'while true; do echo "this is a test message being sent to the pipe" > /home/admin/namedpipe; done' &
And check the reader log with tail -f reader.log
You'll see that after a minute or so it works for a while (the reader receives some messages) and then it stops working (no more received messages are printed to the reader log or it takes a long time to process one). Troubleshoot and fix (for example changing the writer command) so that the writer keeps sending the messages and the reader is able to read all of them.
Test: There should be a process running where a message is being sent to the pipe and that while that is running, another message can be sent to the pipe and read back. The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Scenario: "Yokohama": Linux Users Working Together
Level: Easy
Type: Fix
Access: Paid
Description: There are four Linux users working together in a project in this server: abe, betty, carlos, debora.
First, they have asked you as the sysadmin, to make it so each of these four users can read the project files of the other users in the /home/admin/shared directory, but none of them can modify a file that belongs to another user. Users should be able modify their own files.
Secondly, they have asked you to modify the file shared/ALL so that any of these four users can write more content to it, but previous (existing) content cannot be altered.
Test: All users (abe, betty, carlos, debora) can write to their own files. None of them can write to another user's file. All users can add more content (append)) to the shared/project_ALL file but none can change its current content. The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A Python app serving simulated bank data runs as root and listens on port 20280. The app is managed by supervisor and cannot be stopped or reconfigured to use a different port.
An internal legacy monitoring system expects the service to be available on port 80, but the app is hardcoded to 20280 for security and legacy reasons. Your task is to make the service accessible on port 80 locally.
Scenario: "Rio de Janeiro": Do we have another option?
Level: Easy
Type: Fix
Access: Email
Description: This scenario server is dedicated to Jenkins, a Java application managed by systemd. Jenkins is failing to start. Troubleshoot and find the problem, then apply the solution so Jenkins runs properly.
Test: The service must return the string "Sign in - Jenkins" amongst some other html code. You can check with the command curl -s localhost:8888/login | grep Jenkins | head -n1
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: (NOTE: if you are a Pro user, you cannot SSH directly into this VM; click the "Open the Server Terminal" button to use the web browser instead).
SSH seems broken in this server. The user admin has an id_ed25519 SSH key pair in their ~/.ssh directory with the public key in ~/.ssh/authorized_keys but ssh 127.0.0.1 won't work.
Test: You can ssh locally, i.e. ssh admin@127.0.0.1 works.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A critical health check script at /opt/scripts/health.sh is supposed to run every 10 seconds. This check is triggered by a systemd timer. The script's job is to check the local Nginx server and write its status (e.g., "STATUS: OK") to the log file at /var/log/health.log. The log file is not being updated, and it appears the health check is failing.
Find out why the health check system is broken and fix it. The check will pass once the /var/log/health.log file is being correctly updated by the timer with a STATUS: OK message.
Test: The /opt/scripts/health.sh script writes STATUS: OK to /var/log/health.log every 10 seconds.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A critical backup cron job has silently stopped working 3 days ago. The backup script is located at /opt/backup/backup.sh and should create daily backups in /var/backups/daily/, but no new backups have been created recently.
Looking at the backup directory, you can see old backup files from a few days ago, proving the system used to work. However, there are no error emails, no obvious error logs, and the cron service appears to be running normally.
Fix ALL issues preventing the backups from running, so that backups are created successfully and reliably.
Test directory: /var/backups/daily/ Backup script: /opt/backup/backup.sh
Test: The solution will be validated by checking if a backup file has been created in the last 10 minutes.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Scenario: "Manhattan": can't write data into database.
Level: Medium
Type: Fix
Access: Public
Description: Your objective is to be able to insert a row in an existing Postgres database. The issue is not specific to Postgres and you don't need to know details about it (although it may help).
Helpful Postgres information: it's a service that listens to a port (:5432) and writes to disk in a data directory, the location of which is defined in the data_directory parameter of the configuration file /etc/postgresql/14/main/postgresql.conf. In our case Postgres is managed by systemd as a unit with name postgresql.
Description: There's a web server serving a file /var/www/html/index.html with content "hello sadserver" but when we try to check it locally with an HTTP client like curl 127.0.0.1:80, nothing is returned. This scenario is not about the particular web server configuration and you only need to have general knowledge about how web servers work.
Test:curl 127.0.0.1:80 should return: hello sadserver
Description: There's an Nginx web server installed and managed by systemd. Running curl -I 127.0.0.1:80 returns curl: (7) Failed to connect to localhost port 80: Connection refused , fix it so when you curl you get the default Nginx page.
Test:curl -Is 127.0.0.1:80|head -1 returns HTTP/1.1 200 OK
Description: There's a "dockerized" Node.js web application in the /home/admin/app directory. Create a Docker container so you get a web app on port :8888 and can curl to it. For the solution to be valid, there should be only one running Docker container.
Test:curl localhost:8888 returns Hello World! from a running container.
Description: Try and figure out if you are inside a container (like a Docker one for example) or inside a Virtual Machine (like in the other scenarios).
Test: This scenario doesn't have a test (hence also no "Check My Solution" either).
Description: There is a Python WSGI web application file at /home/admin/wsgi.py , the purpose of which is to serve the string "Hello, world!". This file is served by a Gunicorn server which is fronted by an nginx server (both servers managed by systemd). So the flow of an HTTP request is: Web Client (curl) -> Nginx -> Gunicorn -> wsgi.py . The objective is to be able to curl the localhost (on default port :80) and get back "Hello, world!", using the current setup.
Test:curl -s http://localhost returns Hello, world! (serving the wsgi.py file via Gunicorn and Nginx)
Description: There's an etcd server running on https://localhost:2379 , get the value for the key "foo", ie etcdctl get foo or curl https://localhost:2379/v2/keys/foo
Description: Given the CSV file /home/admin/table_tableau11.csv, find the Electoral District Name/Nom de circonscription that has the largest number of Rejected Ballots/Bulletins rejetés and also has a population of less than 100,000.
The initial CSV file may be corrupted or invalid in a way that can be fixed without changing its data.
Installed in the VM are: Python3, Go, sqlite3, miller directly and PostgreSQL, MySQL in Docker images.
Save the solution in the /home/admin/mysolution , with the name as it is in the file, for example: echo "Trois-Rivières" > ~/mysolution (the solution must be terminated by newline).
Description: A developer put an important password on his webserver localhost:5000 . However, he can't find a way to recover it. This scenario is easy to to once you realize the one "trick".
Find the password and save it in /home/admin/mysolution , for example: echo "somepassword" > ~/mysolution
Description: There are two pods: "logger" and "logshipper" living in the default namespace. Unfortunately, logshipper has an issue (crashlooping) and is forbidden to see what logger is trying to say. Could you help fix Logshipper?
Do not change the K8S definition of the logshipper pod. Use "sudo".
Because k8s takes a minute or two to change the pod state initially, the check for the scenario is made to fail in the first two minutes.
Description: There are three Docker containers defined in the docker-compose.yml file: an HAProxy accepting connetions on port :5000 of the host, and two nginx containers, not exposed to the host.
The person who tried to set this up wanted to have HAProxy in front of the (backend or upstream) nginx containers load-balancing them but something is not working.
Test: Running curl localhost:5000 several times returns both hello there from nginx_0 and hello there from nginx_1
Check /home/admin/agent/check.sh for the test that "Check My Solution" runs.
Description: Find in the file frankestein.txt the second most frequent word and save in UPPER (capital) case in the /home/admin/mysolution file.
A word is a string of characters separated by space or newlines or punctuation symbols .,:; . Disregard case ('The', 'the' and 'THE' is the same word) and for simplification consider the apostrophe as another character not as punctuation ("it's" would be a word, distinct from "it" and "is"). Also disregard plurals ("car" and "cars" are different words) and other word variations (don't do "stemming").
We are providing a shorter test.txt file where the second most common word in upper case is "WORLD", so we could save this solution as: echo "WORLD" > /home/admin/mysolution
This problem can be done with a programming language (Python, Golang and sqlite3) or with common Linux utilities.
Description: A developer created a database named 'main' but now some data is missing in the database. You need to restore the database using the the dump "/home/admin/backup.sql". The issue is that the developer forgot the root password for the MariaDB server. If you encounter an issue while restoring the database, fix it.
"Abaokoro": Restore MySQL Databases Spooked by a Ghost
Scenario: "Abaokoro": Restore MySQL Databases Spooked by a Ghost
Level: Medium
Type: Fix
Access: Paid
Description: There are three databases that need to be restored. You need to create three databases called "first", "second" and "third" and restore the databases using the file "/home/admin/dbs_to_restore.zip". If you encounter an issue while restoring the database, fix it.
Scenario: "Poznań": Helm Chart Issue in Kubernetes
Level: Medium
Type: Fix
Access: Paid
Description: NOTE: Prompt may take a few extra seconds to be responsive while the k3s environment gets ready. Root access is not needed for this challenge ("admin" user cannot sudo).
A DevOps engineer created a Helm Chart web_chart with a custom nginx site, however he still gets the default nginx index.html.
You can check for example with POD_IP=$(kubectl get pods -n default -o jsonpath='{.items[0].status.podIP}') and curl -s "${POD_IP}">.
In addition he should set replicas to 3.
The chart is not working as expected. Fix the configurations so you get the custom HTML page from any nginx pod.
Test: Doing curl on the default port (:80) of any nginx pod returns a Welcome SadServers page. The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: You have been tasked with compressing the file /home/admin/names, which is 35147 bytes, to a size smaller than 9400 bytes. You can use any compressing tool at your disposal (there are many available in the server), also you can modify the file without deleting anything in it. Put the solution (compressed file) in the /home/user/admin/solution directory with the default extension used by the compression tool (example: ~/solution/names.gzip).
Test: The size of the compressed file is smaller than 9400 bytes.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Scenario: "Warsaw": Prometheus can't scrape the webserver
Level: Medium
Type: Fix
Access: Paid
Description: A developer created a golang application that is exposing the /metrics endpoint. They have a problem with scraping the metrics from the application. They asked you to help find the problem.
Full source code of the application is available at the /home/admin/app directory.
"Moyogalpa": Security Snag. The Trials of Mary and John
Scenario: "Moyogalpa": Security Snag. The Trials of Mary and John
Level: Medium
Type: Fix
Access: Email
Description: Mary and John are working on a Golang web application, and the security team has asked them to implement security measures. Unfortunately, they have broken the application, and it no longer functions. They need your help to fix it.
The fixed application should be able to allow clients to communicate with the application over HTTPS without ignoring any checks. (eg: curl https://webapp:7000/users.html) and serve its static files.
Test:curl https://webapp:7000/users.html should return the content of file.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
"Helsingør": The first walls of postgres physical replication
Scenario: "Helsingør": The first walls of postgres physical replication
Level: Medium
Type: Fix
Access: Email
Description: You're setting up a PostgreSQL database with replication, you decided to use Docker along with Docker Compose to make it easier to manage and test, after a few hours of work you finished the job and the master database is up and running, but you're having trouble with the replica.
You need to figure out what's wrong with the replica and fix it.
Since you are using Docker Compose, you can check the status of the running containers using docker compose ps or docker ps will do the job too). You may also want to check the logs of the containers.
All definition for the containers are inside the docker-compose.yml file. You can stand up the environment by running docker compose up -d and set it down by running `docker compose down`.
If you make any change to the docker-compose.yml file, you can restart the containers by running docker compose up -d --force-recreate.
Test: Postgres replica container works.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: There is an nginx service running on port 443, it is the main web server for the company and looks like a new employee has deployed some changes to the configuration of supervisor and now it is not working as expected.
If you try to access curl -k https://bekasi it should return Hello SadServers! but for some reason it is not.
You cannot modify files from the /home/admin/bekasi folder in order to pass the check.sh
Description: You are tasked to add compression to the company website. The website is running on an Nginx server, and you decide to add Brotli compression to it.
Brotli has became very popular these days because of its high compression ratio. It's a generic-purpose lossless compression algorithm that compresses data using a combination of a modern variant of the LZ77 algorithm, Huffman coding, and 2nd order context modeling.
For this purpose, you decided to compile the brotli modules yourself and add them to the Nginx server.
The location of the Brotli source code is at /home/admin/ngx_brotli. The nginx source code (needed to compile the modules) is located at /home/admin/nginx-1.18.0. From the ngx_brotli repository first you need to compile the brotli dependencies and then configure and make modules for Nginx. Afer that you need to add the modules to the Nginx configuration.
After installing the modules, you need to make sure the responses from the server are being server with compression.
Create a port-forward to port 80 from the server to your computer and check the header Content-Encoding, responses must return br for Brotli compression. You can also use curl -H "Accept-Encoding: br, gzip" -I http://localhost to check the header.
Something nice about Brotli is that it fails over to gzip if the client doesn't support Brotli, so curl -H "Accept-Encoding: gzip" -I http://localhost should return gzip instead.
Description: (You can learn about Linux Libraries before starting this scenario).
The Linux shared library liblzma.so has been compromised (the real compromised XZ Utils liblzma has not been used). The liblzma.so at the path /usr/lib/x86_64-linux-gnu/liblzma.so.5.2.5 is the good one. Consider the same library liblzma.so.5.2.5 at other paths as compromised or malicious (ideally we would have used other real versions with different checksums).
Find all instances of this "malicious" liblzma library (remember, it's the same library but in different directory locations) and make it so none of the running processes use it, while the applications "webapp" and "jobapp" (both of which managed by systemd) still run properly (eg, stopping those applications is not a solution).
Test:lsof | grep liblzma.so.5 returns only the liblzma in the path: /usr/lib/x86_64-linux-gnu/liblzma.so.5.2.5
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer created a script /home/admin/readdb.py that tests access to a database. Without modifying the readdb.py file, change the database so that running the script returns the string "John Karmack".
Scenario: "Minneapolis with a Vengeance": Break a CSV file
Level: Medium
Type: Do
Access: Email
Description: Break the Comma Separated Valued (CSV) file data.csv in the /home/admin/ directory into exactly 10 smaller files of about the same size named data-00.csv, data-01.csv, ... , data-09.csv files in the same directory. All the files should have the same header (first line with column names) as data.csv. None of the smaller files should be bigger than 32KB.
Note: unlike the original Minneapolis scenario, here the resulting files have to be proper CSV files.
As a helper tool, you can run the program check_csv.py to check if your data-??.cs files look like proper CSV files.
Test: The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: The Hanoi office has a Linux server with a large number of user accounts and groups. The system administrators need to identify which users belong to multiple groups for better access management.
Given two files, `users.txt` and `groups.txt`, create a new file `/home/admin/multi-group-users.txt` containing the usernames of users who belong to more than one group, one username per line, sorted alphabetically.
The `users.txt` file contains a list of usernames, one per line. The `groups.txt` file contains group names and their members, in the format `group_name:user1,user2,user3`.
There is a web server (Caddy) on HTTP port :80 but curl http://127.0.0.1 doesn't work. Find out what's wrong and make the necessary fixes so the web server returns a URL.
Note: as a limitation, the file /home/admin/db_connector.py must not be modified so that the challenge is considered solved properly. The web server has to respond on the IP address 127.0.0.1; not only on "localhost".
Test: The command curl http://127.0.0.1 returns a URL address.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
"Bengaluru": Kubernetes StatefulSet least known characteristic
Scenario: "Bengaluru": Kubernetes StatefulSet least known characteristic
Level: Medium
Type: Fix
Access: Email
Description: There's a Kubernetes cluster (created with "k3d") with two worker nodes and two pods on the node k3d-cluster-agent-0: a Deployment demo-deployment-... and a StatefulSet demo-statefulset-0. Their manifests are identical except for the different kind of K8s resource.
Make the node hosting the pods unavailable (it "goes down" or "crashes" without being deleted from k8s), for example with: docker stop k3d-mycluster-agent-0.
After waiting for about a minute (tolerationSeconds in the manifest is 30s, we shorten the K8S 5 minutes default so you don't have to wait so much, plus a grace period), both pods are marked as Terminating. While the Deployment pod is evicted and deployed onto the remaining available node k3d-cluster-agent-1, the StatefulSet demo-statefulset-0 is not (Why?).
Make the StatefulSet pod demo-statefulset-0 run on the available node.
Note: you can use k as a shortcut for kubectl.
Test: Node k3d-cluster-agent-0 is NotReady. Both the Deployment and the StatefulSet are running on the node k3d-cluster-agent-1 The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: This is a "hacking" or Capture The Flag challenge. You need to copy the message at /home/user3/secret.txt into the /home/admin/solution.txt file.
Test: Running md5sum /home/user10/secret.txt returns the hash 7fe16554d0b326309d980314cebc2994
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Scenario: "Quito": Control One Container from Another
Level: Medium
Type: Do
Access: Email
Description: You have a running container named docker-access. Another container nginx is present but in a stopped state. Your goal is to start the nginx container from inside the docker-access container.
You must not start the nginx container from the host system or any other container that is not docker-access. You can restart this docker-access container.
Description: You have an Envoy proxy routing traffic to two unhealthy backend services.
When the number of healthy backends falls under a panic threshold (default 50%), Envoy enters a panic mode and it will either send traffic to all upstream hosts or to none at all.
We are simulating this condition by returning an HTTP 503 status code from the /health endpoint in both backends. In our case Envoy is sending traffic to all upstream services.
Your objective is to change the panic Envoy behaviour so that it does not route any traffic to unhealthy services and instead Envoy returns "no healthy upstream". (Do not change anything in the backend services). There can also be other Envoy configuration issues you need to fix.
Test: Running curl localhost:10000 should return no healthy upstream.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: Given the file user_list.txt you must create all the users specified in the file with their corresponding passwords.
The entries in the user_list.txt file are stored as username;password
Test: All users are created with the right password. The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
The objective of this exercise is to delete all the Bash history lines that contain the term foo.
Clearing out or deleting the history file /home/admin/.bash_history is not allowed. Note that in our case, new commands (including the ones to try and delete "foo" from history) are also appended to the history file.
Test: Running history |grep "foo" returns nothing.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A Python web application running on port 5000 from the /opt directory is experiencing severe performance issues; every request takes more than 5 seconds to complete. The application is supposed to use the redis-server cache service for speed.
Your mission is to diagnose the performance bottleneck and restore the application to its normal, fast response time.
Do not change the Python application file slow_app.py.
Test:curl localhost:5000 returns Data from FAST cache!
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer wants to deploy an open-source tool on Kubernetes. The tool unfortunately has limited documentation.
They built a helm chart and a container image. When the application is deployed, for some reason the server in Kubernetes doesn't seem to work but when the binary is started on their laptop/machine it works perfectly.
The application server is deployed by Helm. The command they used is: helm upgrade --install ruaka charts/ruaka.
Debug and help the developer find the issue. NOTE: Do not change or delete any current Helm field value in the chart, only add if needed.
Remember to give enough time to k8S after you apply a change before checking the solution.
Test:kubectl get pod shows the ruaka application pod up and running, while no Helm fields have been taken out from the applicaiton chart.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Scenario: "Campina Grande": Give me my cert, Vault
Level: Medium
Type: Fix
Access: Paid
Description: A web application running at https://nginx.example.com has an expired certificate. Issue a new certificate using the Hashicorp Vault running on the server. The Vault instance is already unsealed and initialized, and you have full admin access with the admin user.
The certificate presented by Nginx is issued by the Vault PKI (check using openssl verify -CAfile /usr/local/share/ca-certificates/vault-pki-ca.crt /etc/nginx/ssl/cert.pem).
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer has been working on Linux deployment scripts on their machine and then transferred the files to a Linux server. However, when they try to execute the scripts, they encounter the mysterious error:
-bash: cannot execute: required file not found
The scripts appear to be syntactically correct, but something is preventing them from executing properly. The developer needs your help to identify and fix the issue so the deployment can proceed.
There are several script files in /home/admin/deploy/ that need to be fixed before the deployment process can work correctly.
Test: All script files in /home/admin/deploy/ should execute without the cannot execute: required file not found error.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer wants to run a program that splits their pile of their data into compressed parts for efficient transport across their network. Unfortunately when the tool runs it never completes.
The application binary in question is called bondo located in /home/admin/bondo.
Run it, then debug and help the developer find the issue.
Test: Executing /home/admin/bondo as admin returns part files generation completed!.
The file /etc/fstab has not been modified and the solution would work on reboot.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: There is a small "C" application in the /home/admin/app directory. Create the Docker container "app" with a small footprint and minimalistic so you get a hello binary that returns a greeting in Atlantean (Docker multi-stage build). The binary application is automatically called when running docker run app
Test:docker run app returns SOO-puhk
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer is having trouble deploying an application on a preconfigured cluster.
The application kilifi is to be deployed on kubernetes in the default namespace. The application server is deployed by helm. The command they used is helm install kilifi charts/kilifi. The application operates correctly with ~210 MB of memory, but 256 MB is recommended.
Swap should remain disabled in the cluster.
Debug and help the developer fix any issue with deployment.
Test: The kilifi application runs properly; it's Service on :3333/healthz returns "kilifi ready to serve".
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: You have a ClickHouse installation CHI running on a Kubernetes cluster and a set of requests (located at ~/data/requests.csv) that you must populate into the http_requests table in the monitoring database (table may not exist in all pod instances). Do this insert in all pod instances of the database. The user and password to connect to the database are default. The keeper pods provide clickhouse replication services.
Test: You are able to query the database and see the data:
clickhouse-client -h --password default -q 'SELECT COUNT(*) FROM monitoring.http_requests'
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A Redis master-replica setup is running on this server, with the master on port 6379 and the replica on port 6380. Both instances show as "connected" when you check their status, but data synchronization has silently broken.
Recent writes to the master don't appear on the replica, even though there are no obvious errors in the logs and both Redis instances appear healthy.
Fix the replication issues so that data written to the master (port 6379) immediately appears on the replica (port 6380) without data loss.
Description: The security team has asked again Mary and John to implemente more security measures. Unfortunately, this time they have broken the LAMP stack (Apache with PHP) so the frontend is unable get an answer upstream, thus, they need your help again to fix it.
The fixed application should be able to serve the content from the webserver, the problem is a network connectivity, although the logs have valuable informatiion, it has nothing to do with the configuration of the apache server.
Test:curl localhost | head -n1 returns SadServers - LAMP Stack
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: While working with a distro with a very small footprint, we just found out that there are some basic commands not present, this was supposed to be a security feature, after all this is just a small server, however, the web content was not deployed. Your task is to decompress the file /home/admin/web.zip and move the file home.html in it to /var/www/html/index.html
Test: The service must return the string "Homepage". You can check with the command curl -s localhost
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: Can't ping google.com. It returns ping: google.com: Name or service not known. Expected is being able to resolve the hostname. (Note: currently the VMs can't ping outside so there's no automated check for the solution).
Test:ping google.com should return something like PING google.com (172.217.2.46) 56(84) bytes of data.
"Bern": Docker web container can't connect to db container.
Scenario: "Bern": Docker web container can't connect to db container.
Level: Hard
Type: Fix
Access: Email
Description: There are two Docker containers running, a web application (Wordpress or WP) and a database (MariaDB) as back-end, but if we look at the web page, we see that it cannot connect to the database. curl -s localhost:80 |tail -4 returns:
<body id="error-page"> <div class="wp-die-message"><h1>Error establishing a database connection</h1></div></body> </html>
This is not a Wordpress code issue (the image is :latest with some network utilities added). What you need to know is that WP uses "WORDPRESS_DB_" environment variables to create the MySQL connection string. See the ./html/wp-config.php WP config file for example (from /home/admin).
Test:sudo docker exec wordpress mysqladmin -h mysql -u root -ppassword ping . The wordpress container is able to connect to the database in the mariadb container and returns mysqld is alive.
Scenario: "Karakorum": WTFIT – What The Fun Is This?
Level: Hard
Type: Fix
Access: Paid
Description: There's a binary at /home/admin/wtfit that nobody knows how it works or what it does ("what the fun is this"). Someone remembers something about wtfit needing to communicate to a service in order to start. Run this wtfit program so it doesn't exit with an error, fixing or working around things that you need but are broken in this server. (Note that you can open more than one web "terminal").
"Singara": Docker and Kubernetes web app not working.
Scenario: "Singara": Docker and Kubernetes web app not working.
Level: Hard
Type: Fix
Access: Email
Description: There's a k3s Kubernetes install you can access with kubectl. The Kubernetes YAML manifests under /home/admin have been applied. The objective is to access from the host the "webapp" web server deployed and find what message it serves (it's a name of a town or city btw). In order to pass the check, the webapp Docker container should not be run separately outside Kubernetes as a shortcut.
Test:curl localhost:8888 returns a value from the webapp deployed Kubernetes pod.
Scenario: "Hong-Kong": can't write data into database.
Level: Hard
Type: Fix
Access: Paid
Description: (Similar to "Manhattan" scenario but harder). Your objective is to be able to insert a row in an existing Postgres database. The issue is not specific to Postgres and you don't need to know details about it (although it may help).
Postgres information: it's a service that listens to a port (:5432) and writes to disk in a data directory, the location of which is defined in the data_directory parameter of the configuration file /etc/postgresql/14/main/postgresql.conf. In our case Postgres is managed by systemd as a unit with name postgresql.
Description: A user client was added to the server, as well as their SSH public key. The objective is to be able to SSH locally (there's only one server) as this user client using their ssh keys. This is, if as root you change to this user sudo su; su client, you should be able to login with ssh: ssh localhost.
Test: As user admin: sudo -u client ssh client@localhost 'pwd' returns /home/client
Description: There is a secret stored in a file that the local Apache web server can provide. Find this secret and have it as a /home/admin/secret.txt file.
Note that in this server the admin user is not a sudoer.
Also note that the password crackers Hashcat and Hydra are installed from packages and John the Ripper binaries have been built from source in /home/admin/john/run
There is a one-class Java application in your /home/admin directory. Running the program will print out a secret code, or you may be able to extract the secret from the class file without executing it but I'm not providing any special tools for that.
Put the secret code in a /home/admin/solution file, eg echo "code" > /home/admin/solution.
Description: There is a RabbitMQ (RMQ) cluster defined in a docker-compose.yml file.
Bring this system up and then run the producer.py script in such a way that is able to send messages to RMQ. In particular you have to send the message "hello-lwc".
- RMQ is a queuing system: messages are put in the queue with a "producer" and they are taken out from the other side by a "consumer". The queue name has to be the same for both.
- To send the message "hello-lwc": python3 ~/producer.py hello-lwc. Should return Message sent to RabbitMQ. "IncompatibleProtocolError" means RMQ is not working properly.
- To test consuming it: python3 ~/consumer.py, this will retrieve the next message from the queue and print it. Once everything is working send more than one message so there's at least one in the queue when the validation runs.
- Do not change the consumer.py and producer.py files; if you do the Check My Solution will fail.
Test:python3 ~/consumer.py returns hello-lwc
See /home/admin/agent/check.sh for the exact test.
Description: There is a web server on :5000 with a form. POSTing the correct form password into this web service will return a secret.
Save this secret provided by the web page (not the password you sent to it) to /home/admin/mysolution, for example: echo "SecretFromWebSite" > ~/mysolution
TIP: a developer worked on the web server code in this VM, using the same 'admin' account.
Description: You are working as a DevOps Engineer in a company and another team member left the company and left the docker-compose.yml of a database-backed web application unfinished.
Generally, the problem revolves around the database migration and docker compose.
Additionally on front of the application there is an Nginx server and you need to fix the proper access to it as well.
Scenario: "Zaragoza": Test changing critical files
Level: Hard
Type: Do
Access: Paid
Description: The goal is to make the script /home/admin/agent/check.sh return OK, without editing the original /etc/hosts file.
Think of testing changes in the critical directory /etc in a safe way. In this case, adding "127.0.0.1 my.local.test" to /etc/hosts .
There would be many ways of trying to do this with "sudo" access, like the usual procedure of making a copy of the config file, editing there and copying or renaming back to the original file. In our case, to avoid all those simple solutions, there is no general "sudo" privileges in this scenario (but there may be for some commands).
Test: The string my.local.test is in /etc/hosts
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
"Amygdala": Do you have enough insight to see the secrets?
Scenario: "Amygdala": Do you have enough insight to see the secrets?
Level: Hard
Type: Fix
Access: Paid
Description: Troubleshoot and fix a Kubernetes web application running in the app namespace. Make the deployment run successfully so that it returns Hello handsome! when you curl it.
Fix first your admin user access to the local Kubernetes cluster; the KUBECONFIG environment variable must be set to $HOME/.kube/config.
You have full admin access to a Vault server (containing the secrets you need) from the admin user. All the used manifests for the application are placed on the /home/admin/manifests directory.
Test: Running: POD_IP=$(kubectl get po -n app -l app=app -o jsonpath='{.items[0].status.podIP}') curl http://$POD_IP returns Hello handsome!.
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: A developer wants to upgrade their stateful application. This application handles their archives/backups.
The application tigoni is deployed on kubernetes in the default namespace. The application server is deployed by Helm. The command they used is helm install tigoni charts/tigoni.
Upgrade the tigoni application to v2.0.0. The image already exists in the local repository. Debug and help the developer fix any issue with the upgrade. Everytime v1.0.0 is launched the archiving code starts on a clean slate.
Test: The tigoni pod with version v2 runs correctly (its endpoint :3000/healthz displays serverVersion:v2)
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
Description: You need to build and push a docker image without changing the Dockerfile to your company's Harbor registry, which is running at harbor.sadservers.local, with its home directory at /opt/harbor. You have full admin access with admin:Harbor12345 credential. The source code and the Dockerfile are in the ~/app directory. The image name must be harbor.sadservers.local/images/app:1.0.0. It is also expected that the application will be up and running at localhost:5000 in a container named app.
IMPORTANT. Do not: 1. Generate new internal certificates 2. Change the Dockerfile 3. Change the /opt/harbor.yml file
Test: You are able to pull the application image from Harbor: docker rmi harbor.sadservers.local/images/app:1.0.0 docker pull harbor.sadservers.local/images/app:1.0.0
You can access the application; curl localhost:5000 returns Hello world!
The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.
