Lab1 Introduction to System Administration

Welcome to the System Administration course. Before getting started, please make sure you have read the following information:

• Courses Homepage for information about the Course Info
• Lab1 slides for more detailed Course Information.
• Slack page for communication through Slack.

For any questions, we recommend using the Slack channels, as this will also make answers visible to other people.

Labs

This course is set up mainly utilizing the Courses pages, all labs every week follow the same format - a weekly guide in the Practicals page that works you through setting up a system or a service, or some closely related systems and services. Often enough, a next week's lab might need settings to be changed in the previous lab's topic, for example, the web servers lab will require changes in things done in the domain name servers lab. That's just how IT works.

Scoring

During the course, you will be monitored and scored by a scoring server: https://scoring.sa.cs.ut.ee . This site monitors the progress of all the labs that you complete. When you are completing labs, you can see that you did everything right when monitoring goes green.

The credentials are to access the website:

User: student Password: SysAdm2022%

Once you access the scoring site, you can search for Services on the left side panel. When you click on it, a new view appears, where there's a host called "Lab1". From there, search a line with your username in it (it appears for the first time a bit after you log into lab1.cloud.ut.ee). When this line goes green, you have completed this week's task.

During the next weeks, when you get your own personal VM, you will have a line with your VMs name in the list. Every week, as we publish another lab with tasks, the monitored services list will also expand.

When monitoring your personal VMs, there are two types of checks - with one we log into your machine and check whether something looks as it should, and the other option is to query your machine from the outside world. This means that you can't expect things in Lab6 to work when Lab2 is not done, as, for example, we can't access your machine, because Lab2 is where you set our access up.

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Remembering *NIX

During this week we will play through the exercises refreshing your UNIX knowledge. Starting from the next week we start building the real server-side service infrastructure. Therefore we find it critical for you to feel fluent with the command-line interface (CLI) of Linux. The outline of this lab is as follows:

• Helpful materials
• CTF (this part is graded)
• Cool Games

Helpful materials

Before we get started with the practical part of the lab, let's go over where to find information, as that is a large part of this whole course. Every lab will have new commands, systems, configuration files, log file locations, and weird error outputs, which is why we strongly recommend utilizing google to its full extent and to talk with each other!

At first, writing up commands that you won't remember is a very good idea. We will never prevent you from being able to look at your notes, even during the exam!

This means that if you want, you can make a cheat sheet, or just write up any commands that you think you will not be able to remember.

Automation is also encouraged during the labs and the exam - during the following weeks we will also be teaching how to use a tool called Ansible, which will take care of config management and more. The third lab will be about Ansible best practices, and after that we add extra examples and guides about Ansible into the weekly labs as well. A well-written Ansible playbook could in theory allow you to pass the exam in just a few minutes, so keeping it up to date might prove invaluable.

We will also try to provide you with informational visualizations to further your understanding. We hope these to be useful!

There are also remotely hosted resources that are very useful:

• Shell Commands Explainer
• Bash Guide for Beginners

Especially Shell Commands Explainer, which takes the input command line, and tries to fully explain what is going on. Works for surprisingly many commands.

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CTF

We now get to the practical part of the lab. Before we can do anything, we need to get inside the environment where we can play around without having to worry about our machines.

Accessing the Sandbox machine

First, make sure that you are connected to the University of Tartu network.

Remotely (not in the lab), this is achieved by using the University of Tartu VPN service. The guide for that can be found at https://wiki.ut.ee/pages/viewpage.action?pageId=17105590.

When you are using the classroom computers or University WiFi, you should be fine without the VPN.

Moving from one host to another on Linux systems is usually done by utilizing a protocol called SSH (Secure Shell). This can be used to login into another machine.

  The syntax usually follows like this: ssh <username>@<hostname>
  Example: ssh mouse@lab1.cloud.ut.ee

Let's log into a machine called lab1.cloud.ut.ee with our University of Tartu username and password.

The way to do this depends on which operating system you use currently:

For Linux/Mac (the classroom machines) users this can be done by opening your terminal application, and inserting the following command to the command line ssh <username>@lab1.cloud.ut.ee . You will be asked whether you trust the host and for your University of Tartu password. You can tell whether you were successful logging in when you are not getting an error and if the shell prompt changes. Also, the output of commands whoami, hostname and pwd should be different from your own machine.

Windows users have two options:

• Windows Subsystem for Linux - WSL(more info at https://www.microsoft.com/en-us/p/ubuntu/9nblggh4msv6?activetab=pivot:overviewtab). Using WSL grants you the ability to open a Linux terminal in Windows, to use the ssh command as mentioned above. WSL is harder to set up, but easier and more convenient to use in the future, as it emulates the whole command line.
• Software called PuTTY, that allows the creation of an SSH connection to the server. Putty is very easy to run, but in the future might cause you to need to jump through extra hoops to do some stuff, like add an SSH key. A guide on using PuTTY can be found on the University HPC page https://docs.hpc.ut.ee/ssh/.

CTF Excercise

Capture The Flag (CTF) is a form of exercise where the task is to find very specific "flags", hidden in the system or software by competitors or organizers. This is very prevalent in especially Cyber Security, and if you like the following game, make sure to check out https://overthewire.org/wargames/bandit/.

In our case, we have prepared a small CTF as a way to test your Linux knowledge. Do not worry if you cannot do every task outright, some of these are deceptively difficult.

If you cannot think of a solution, do not know how to do something, or want an explanation, make sure to ask a teacher either directly or by using Slack.

Task 1 - A file with Flag inside in local directory:

Task 2 - Flag as an output of a command from history:

Task 3 - A file with Flag in the name inside a subdirectory:

Task 4 - A Flag in a log file:

Task 5 - Flag inside a system file:

Task 6 - Flag received by executing a binary:

Task 7 - A Flag in the output of a curl command:

Task 8 - A Flag in the output of nmap command:

Task 9 - Flag can be received by sending a message to a port on localhost in the range 31000 to 32000:

NB! The last task is monitored by the scoring server. It checks whether a correct username has been input as data into the port. It might take up to 5 minutes for monitoring to pick this up.

Once that's green, you're done with this week's lab. Congratulations!

Epilogue

By the end of the lab, make sure you have done all the following things, as a preparation to the next weeks:

• Have the capability of SSHing into a Linux host
• Are able to connect to the University of Tartu VPN (personal machines).
• Can access the Scoring website (https://scoring.sa.cs.ut.ee) with your (preferably personal) machines.
• Have access to our course's Slack channels.
• Are knowledgeable about the topics and can find information related to the course.
• Have brushed up your google skills.

If missing anything, ask!