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ITEC 2210 Cheat Sheet by

linux     server     networking

Troubl­esh­ooting

1.Find out what the problem is, which should have EAR(ex­pected, actual, reprod­uction)
2.Triage the Situation, make sure the system is still in as good of a condition under the circum­sta­nces.
3.Examine as best you can inc. Logs.
4.Diagnose problem using elimin­ation, successive refine­ment, bisection. You can use elimin­ation, bisection, or successive refine­ment.
5/6. Test the changes and "­Cur­e"(D­eploy)

TCP/IP

4 Layer System:
Applic­ation Layer(Like Youtube)
TCP(Tr­ansport Layer): Wants to know how it's going to get to it's locati­on(also makes it a packet at that point)
Internet (IP) Layer: Uses IP addresses to send the packets through a network interface to an IP(Which works like a house address)
Network Interface: This is how a packet get's transf­err­ed(Ie. Wifi, Ethernet, Etc.)

TCP Handshake: (A > B) SYN, (B > A) ACK-SYN, (A > B) SYN.

UDP is stateless and has minimal overhead, packet has addressing and data with dupe protec­tion.

Vlans are their own networks, to traverse VLANs
 

Launching a Service

1. Define the ready list by Must have features, would be nice features, bugs and regres­sions, assertions and approvals.
2. Work on the ready list
3. Launch the beta with staging enviro­nme­nts­(de­v-Q­A-U­AT-­bet­a-prod)
4.Launch production
5.Capture Lessons by making sure mistakes won't be repeated again.
6.Repeat

Linux Commands

cat - concatenate files and print the standard output
id - prints real and effective user and group IDs
sudo- executes commands as a root user
adduser - add a user or group to the system
ctlr+l - clear terminal
ls - list the directory
touch - changes the file timestamps
chown - change the file owner and group
chgrp - change the group ownership
chmod - change file access permissions
apt-get/apt- get packages/install applications
tree- like ls but listing the content of directories
ln- make a symbolic link between files
dig- performs dns lookups
host - resolve a hostname into a IP address
whois - tells you who owns the ip/hostname
 

Containers and VM's

Types:
IAS(In­fra­str­ucture as a Service), Vendor gives Infras, you do everything else on your own
PAS(Pl­atform as a Service), run an applic­ation using framework or enviro­nment specific to a vendor
SAS(So­ftware as a Service) basically Youtub­e/G­ithub.
VM's:
HVM(Needs to pause VM to use hardware such as a sata contro­ller)
PV(Par­avi­rtu­ali­zation) just sends the I/O calls directly to the VMM.
Contai­ners:
Basically VM's but with no set resources.

Networking

RING Topology
It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.
STAR Topology
In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
TREE Topology
It has a root node and all other nodes are connected to it forming a hierarchy. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).

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