Thanh Nguyen memoryonrepeat

From "Unix and Linux system administration handbook - 5th ed"

Process & threads: Use strace for deep debugging
For risky commands i.e rm, try with -i (interactive) for confirmation first

From sadservers.com

Scenario 1 (figure out which process is writing to some files):
- fuser <filename> (fuser ~ find user --> return list of processes using the supplied file)
- Can also use lsof | grep <filename>
Scenario 2 (get most frequent visitor's IP from access log): awk '{print $1}' access.log | sort | uniq -c | sort | tail -1
Scenario 3 (find which port to knock): Using nmap against all ports nmap -p- localhost

Arithmetic can be seen as a type of transformation
- Useful when dealing with matrix
Can also apply to dot product - measurement of "directional growth" obtained by applying one vector on top of another vector

Use kubectx for switching between contexts / namespaces
For all commands should specify --namespace <NAMESPACE> or --all-namespaces or kubectl will use default namespace
kubectl auth can-i create deployments --namespace <NAMESPACE> --> Check deployment permission
General grammar: kubectl <verb> <noun> [options]
https://www.digitalocean.com/community/tutorials/how-to-inspect-kubernetes-networking
kubectl get pods --namespace=<NAMESPACE> -o wide | grep <SERVICE> --> Get all pods running a service
kubectl exec -it <POD> --namespace <NAMESPACE> -- /bin/bash --> Open shell inside some pod. Can also do other commands
Port forwarding to access service from localhost (Helm chart message upon successful deployment)

What we want to do is take our instincts and then find an ethical system that’s consistent with them, not the other way round.

--> Implication: There is no ground truth to rely on at the beginning. Ethical system is simply a model to approximate truth. Therefore we can only rely on our instinct which is the closest thing to truth that we have, and adjust our model, not try to fit the truth into an arbitrary model.

Find a duality. Play duels against each other. What if unstoppable force meet immovable object?
Try adding a new dimension and look at the problem from that dimension
Think of locality of reference. How to / what does it mean to approach the problem from either spatial / temporal locality ? Is there any other locality (i.e different dimension) that can be used?
Reduce to first principles by applying Socratic methods or Five whys
Inverse thinking --> analyze backwards
Solve a special case / solve a generalized case
Max >= average, min <= average (any more general implications?)
Second-order thinking -> try to think ahead more than 1 step
Think about energy: nature flows in the most optimal way (water from high to low places etc..) --> implications ?
Think about entropy: in closed systems entropy always increa

To keep track of intermediate result along a path, record a var together with the node that get pushed to stack / queue. Example: queue = [(node value, current result along path)]
During graph search, can override calculated result to make graph simpler for next search iteration Example: https://github.com/memoryonrepeat/brainteasers/blob/master/leetcode/numberofislands.py

To practice:

Find largest k elements (in terms of value etc...) in a collection. What to do when facing this pattern ?

Sweep line technique

Inspired by computational geometry. Ideal for problems involving segments / intervals

https://www.shortcutfoo.com/app/dojos/sublime-text-3-mac/cheatsheet

Navigation

CTRL + g: Go to line #
CTRL + m: Go to matching bracket

Selection

CTRL + SHIFT + m: Select function currently enclosed by current bracket (repeat to select those enclosed by outside brackets)
CMD + l: Select current line (repeat to select next line)
CMD + d: Select current word (repeat to have more cursors to hightlight same word at other locations, then any change will be applied to all selections - very useful for refactoring) ---> CMD + k + CMD + d: Skip current match

	version: '3'
	services:
	fcg-mysql:
	image: mysql:5
	command: --default-authentication-plugin=mysql_native_password --lower_case_table_names=2
	environment:
	MYSQL_ROOT_PASSWORD: ""
	MYSQL_ALLOW_EMPTY_PASSWORD: "yes"
	MYSQL_ROOT_HOST: "%"
	expose:

	# /cpu/{sub(/requests/, "found!!!!", last)} NR>1{print last} {last=$0} END {print last}

	{
	# $0 is current line
	if ($0 ~ /cpu/ && previous ~ /requests/){
	sub(/cpu: "0.1"/,"cpu: \"0.01\"",$0)
	print(previous)
	}
	else if ($0 ~ /cpu/ && previous ~ /limits/) {
	sub(/cpu: "0.1"/,"cpu: \"1\"",$0)

	// https://pm2.io/doc/en/runtime/reference/ecosystem-file/

	const appList = [
	'auction',
	'auth',
	'booking',
	'car',
	'cardata',
	'contact',
	'document',