## 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?