ip address (ip a)

ifconfig (deprecated)

ping -v4 <IP Address>

nmap <IP Address>

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.

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

arp (being deprecated)

ip neighbor

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.

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.

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

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

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>

Bourne-Again Shell

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.

ln -s TARGET LINK_NAME

ln - make links between files

-s - Specifies to make a soft link

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.)

Modify date modified of a file.

Wire Crimping

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

T-568A

T-568B

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.

IPMI (Intelligent Platform Management Interface)

HP: LightsOut

Dell: DRAC (Dell Remote Access Controller)

top

htop

ps

uptime

openssh-server

sshd

lspci

lsusb

Freebie! Any answer is okay!