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Networking
#1

How do you find the IP address of a computer on Linux?

ip address (ip a)

ifconfig (deprecated)

#2

What is a way that you can test to see if you are able to access a computer on a network?

ping -v4 <IP Address>

nmap <IP Address>

#3

In the string, "192.168.2.1/24", What does "/24" represent?

CIDR Notation (Classless Inter-Domain Routing)

 

192.168.2.1/24 represents the IPv4 address 192.168.2.1 and its associated routing prefix 192.168.2.0, or equivalently, its subnet mask 255.255.255.0, which has 24 leading 1-bits.

#4

DHCP assigns IP address... but what else can it define?

  • Hostnames
  • Custom Routing
  • Default Gateways
  • Subnet
  • DNS
  • Default Domain
#5

What command would you use to figure out MAC to IP/hostname correlations?

arp (being deprecated)

ip neighbor

IPTables
#1

What is IPTables?

A user-space application program that allows a system administrator to configure the tables provided by the Linux kernel firewall and the chains and rules it stores.

#2

What are basic chains that IPTables is usually setup with?

PREROUTING: Packets will enter this chain before a routing decision is made.

INPUT: Packet is going to be locally delivered. It does not have anything to do with processes having an opened socket; local delivery is controlled by the "local-delivery" routing table: ip route show table local.

FORWARD: All packets that have been routed and were not for local delivery will traverse this chain.

OUTPUT: Packets sent from the machine itself will be visiting this chain.

POSTROUTING: Routing decision has been made. Packets enter this chain just before handing them off to the hardware.

#3

What command would you use to save the current ruleset in IPTables?

iptables-save > /etc/iptables/iptables.rules

#4

What command would you use to open port 80 on the current machine?

iptables -A INPUT  -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT
#5

What command would you use to redirect incoming traffic from port 80 to another machine?

iptables -A PREROUTING -d <incoming ip interface>/32 -p tcp -m multiport --dports 22,80,443,6667,3000 -j DNAT --to-destination <to ip address>

 

iptables -A POSTROUTING -s <to ip address>/32 -o <Interface name> -j SNAT --to-source <incoming ip interface>

Bash
#1

What does BASH mean?

Bourne-Again Shell

#2
This famous string ":(){ :|: & };:", is also known as...

Fork Bomb

 

:() means you are defining a function called :

{:|: &} means run the function : and send its output to the : function again and run that in the background.

The ; is a command separator, like &&.

: runs the function the first time.

#3

What is the linux equivalent to making a shortcut to a file in another location?

ln -s TARGET LINK_NAME

 

ln - make links between files

 

-s - Specifies to make a soft link

#4

What does this command do?

 

`chmod 123 filename`

Change the permission on the "filename":

Owner: Execute Only

Group: Write Only

Others: Write and Execute

(This is a weird permission set... don't actually use this.)

#5

The common tool "touch" can be used to create a file, however what is the original intent for this tool?

Modify date modified of a file.

Physical
#1

What is the process of connecting RJ-45 to CAT cables called?

Wire Crimping

#2

Why are most CAT cables come as twisted pairs?

Twisting pairs of wires helps mitigate noise and interference from outside sources.

#3

What is the common wiring standard for ordering the twisted pairs in a RJ-47 connector called?

T-568A

T-568B

#4

What is the difference between registered and unregistered memory?

Registered (also called buffered) memory modules have a register between the DRAM modules and the system's memory controller. They place less electrical load on the memory controller and allow single systems to remain stable with more memory modules than they would have otherwise.

 

Conventional memory is usually referred to as unbuffered memory or unregistered memory.

#5

What modules to server need to provide out-of-band remote managment?

IPMI (Intelligent Platform Management Interface)

 

HP: LightsOut

Dell: DRAC (Dell Remote Access Controller)

Tools
#1

What tool would you use to figure out processes running on a machine?

top

htop

ps

 

#2

What common linux command would you use to find out how long this computer has been on?

uptime

#3

What common server daemon would you use to administrate a linux computer remotely with?

openssh-server

sshd

#4

What command would you use to figure out pci devices connected to your linux computer?

lspci

lsusb

#5

Freebie: Name your favorite command to use.

Freebie! Any answer is okay!

Final Question

How many physical servers does ACM have and are in use right now!?

43 active physical servers right now.