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## Flashback in lesson 2	– Back to lesson 1
•	Why do we talk about GNU/Linux?
•	Describe in your own words: what is a kernel?
•	What is the difference between Open Source and Free?
•	How is the ‘Administrator’ user called? (uid?)
•	What does MBR stand for and how does it work?
•	What are the limitations of MBR? (Solution?)
•	What is swap en what is it used for?
•	How is the first disk of the SCSI-bus called in linux? (1st partition of that disk?)
•	Tell something about these concepts: package, repository, dependency
•	Explain the bootprocess of a linux-based server.
•	Which command can be used to manipulate packages? (search, install, remove, …)
•	What is the difference between “apt update” and “apt upgrade”?
•	Which protocol makes the link between MAC address and IP address?
•	Which command gives you the current ARP-table?
•	What are the 5 layers of the TCP/IP network model?
•	How do you find the MAC-address of a network interface?
•	What does swapiness mean?
•	What is meant with the term Linux ‘distribution’?

## Flashback in lesson 3	Back to lesson 2
•	Using which command can you request the current working directory?
•	What is meant with the term ‘runlevel’ in linux?
•	What is single user mode?
•	What is / are the most common runlevel(s) under linux?
•	Where on the filesystem can you find devices of your linux system?
•	What is the home directory of the user root?
•	Describe the required steps to add a disk to a linux virtual machine.
•	Why is it important that a partition is correctly aligned?
•	How do you make sure with the tool parted that your partition is correctly aligned?
•	What command do we use to create a filesystem in a partition?
•	What do you need to do to have a mounted filesystem available even after reboot?
•	Tell something about the proc filesystem
•	Where can you put temporary files in a linux system?
•	What should you be aware of when using /tmp?
•	How can you quickly search through your previously used commands?
•	What can you use a bind mount for?
•	What is swap and what is it used for?
•	What are the limitations of MBR?
•	Explain in your own words: what is a file descriptor? (lab)

## Flashback in lesson 4	Back to lesson 3
•	What is meant by the term journalling for filesystems?
•	Why is journalling used with filesystems?
•	Give 2 examples of filesystems under linux that use journalling.
•	How can you find out which kernel modules are currently loaded?
•	Which command can you use to load a kernel module? And which to 'unload' a kernel module?
•	How many disks do you need at least to build a RAID10 system? Why?
•	What is meant by a 'Copy On Write' filesystem?
•	What are the advantages of a CoW filesystem?
•	What are snapshots (in the context of storage systems)?
•	What are the disadvantages of a CoW filesystem?
•	Why do you still need backup when you have RAID1 and have snapshots?
•	How can you find out which 'type' is a file? There are no extensions.
•	What is an inode?
•	What is the difference between a softlink and a hard link?
•	At the output of the command ls -la: Which values can the first character of the line have and what do they mean?
•	At the output of the command ls -la: Which possible values can the 3 groups of 3 characters have to describe the rights?
•	With what command can you 'change' the 'owner' of a file or directory?
•	With which command can you 'change' the rights of a file or directory?
•	What does number 5 mean when you use it to determine file system permissions?
•	What does number 7 mean when you use that to determine file system rights? Explain why.
•	Which command do you use to cut structured input at a specific location?
•	Which command do you use to display the first 16 lines of a text file?
•	Which command do you use to display the last 12 lines of a text file?
•	How can you find out how long it has been since a linux system was rebooted?
•	Which command can you use to find out all the modified files from the last 24 hours?
•	Which command can you use to get an overview of all daemons that are currently active in your system?

## Flashback in lesson 5	Back to lesson 4
•	What does ‘piping’ mean?
•	What is a prerequisite for using the command ‘uniq’ ?
•	What is the difference between the following 2 commands?
•	Which are the 2 output streams in linux, and what do they contain?
•	What is ‘exit code’?
•	Why is the exit code useful?
•	What different values can the exit code be?
•	What is the exit code for success?
•	How do you request the exit code?
•	How do you turn a command into a job?
•	How do you pause a job?
•	What command shows the list of all running or paused jobs?
•	How do you re-activate a paused job?
•	What does the command ‘screen’ do?
•	What is meant by the term ‘signal’?
•	How do you send a signal to a process?
•	How do you specify which process?
•	Give 2 examples of signals.
•	Is a systemload of 23 problematic? Explain.
•	What process has PID 1?
•	Where do you know this process from?

## Flashback in lesson 6	Back to lesson 5
•	In what file can you find the hashes of passwords?
•	What command do you use to remove a user?
•	How can you change the password of a different user than your own user?
•	How do you add an existing user to an existing group?
•	How do you give someone sudo rights?
•	Give 2 differences between telnet and ssh.
•	There are 2 types of tunnels you can create with SSH? Which are that?
•	With which tool can you get information about who owns domain names, IP addresses, ... on the internet?
•	With which command do you gain insight into the open files of a process?
•	Can you disable and enable CPUs in a multi-processor Linux system on-the-fly (so without a reboot)?
•	How can you find out which users are all logged in to your system?
•	How do you get information about the CPU (or CPUs) that are in a Linux system?
•	With which command can you send a message to all users at the same time on a system?
•	Which Linux tool can you use to calculate IP addresses, subnets, ...?
•	What are the 5 layers of the network model?
•	Can you run multiple services on 1 server?
•	How do we identify different instances of layer 2?
•	What is a firewall?
•	Name 3 categories of firewalls.
•	What is known as kernel space?
•	What is the opposite of kernel space?
•	Explain: conntrack
•	On which layer of the network model does routing take place?

## Flashback in lesson 7	Back to lesson 6
•	How do you request the route table?
•	With which command do you check how much free disk space there is?
•	With which command do you check which filesystems are mounted where?
•	With which command can you request the MAC address of a network interface?
•	With which command do you request the table that makes the link between IP address and MAC address?
•	Wireshark is a tool for capturing network traffic. Which CLI tool can capture network traffic in Linux?
•	With which command do you get an overview of all processes and how much CPU, memory, ... these take up?
•	What is the systemload?
•	How can you request which services listen on which ports?
•	What is the most commonly used filesystem under linux?
•	What is journalling?
•	What does copy-on-write mean?
•	What is meant with a multi-homed system?
•	How can you verify if a multi-homed system can send traffic from one NIC to another?
•	What does the target ‘MASQUERADE’ do in iptables?
•	How many tables does iptables have? Also give the name of the 2 most commonly used ones.
•	How many chains are there in iptables? Which ones do you find in the FILTER-table?
•	How many netfilter-hooks are there in the linux kernel?
•	Give 3 ‘states’ of a connection.
•	What does ‘DORA’ stand for in the context of DHCP?
•	Where on the filesystem can you find the system-wide host-specific configuration files?
•	What is meant with ‘split brain’?
•	Which port(s) does DNS listen on?
•	What is the name of the type of resource record in DNS that links a name to an IP address (forward lookup).
•	With which command can you perform DNS queries and get (many) details?

## Flashback in lesson 8	Back to lesson 7
•	Give 3 loadbalancing algorithms.
•	What is a potential risk with (W)LC?
•	What are things you can configure for a healthcheck?
•	What are the 3 ‘building blocks’ of a haproxy config?
•	Give 3 levels of loadbalancing with haproxy.
•	What does stickiness mean?
•	How can you get an overview of the health of your haproxy setup?
•	What is the difference between High Availability & Load Balancing?
•	How can you find you what type of file (textfile, binary, …) something is?
•	What command do you need to change access rights of a file?
•	What command do you need to change the owner and/or group of a file?
•	What are the 2 output streams in linux?
•	How can you interfere with / influence the 2 output streams?
•	Give at least 3 ways to get an overview of running processes on your system.
•	How can you find out what the parent of a process is?
•	What is being passed to the parent of a process?
•	What is a signal?
•	How can you send a signal to a process?
•	How do you arrange for a filesystem which you mounted to become available after reboot?
•	What is swap and what is it used for?
•	What are the restrictions of MBR?
