Frederick Nyawaya nightcrawler-

psql: FATAL: Peer authentication failed for user “postgres” (or any user)

The connection failed because by default psql connects over UNIX sockets using peer authentication, that requires the current UNIX user to have the same user name as psql. So you will have to create the UNIX user postgres and then login as postgres or use sudo -u postgres psql database-name for accessing the database (and psql should not ask for a password).

If you cannot or do not want to create the UNIX user, like if you just want to connect to your database for ad hoc queries, forcing a socket connection using psql --host=localhost --dbname=database-name --username=postgres (as pointed out by @meyerson answer) will solve your immediate problem.

But if you intend to force password authentication over Unix sockets instead of the peer method, try changing the following pg_hba.conf* line:

from

	a=1
	for i in *.png; do
	new=$(printf "%04d.png" "$a") #04 pad to length of 4
	mv -i -- "$i" "$new"
	let a=a+1
	done

	# This file should contain all the record creation needed to seed the database with its default values.
	# The data can then be loaded with the rails db:seed command (or created alongside the database with db:setup).
	#
	# Examples:
	#
	# movies = Movie.create([{ name: 'Star Wars' }, { name: 'Lord of the Rings' }])
	# Character.create(name: 'Luke', movie: movies.first)

	# Seed file:
	# /home/frederick/Dev/data/legacy-medexam

	// Gets the version code -- number of git tags to this end
	def getVersionCode = { ->
	try {
	def code = new ByteArrayOutputStream()
	exec {
	commandLine 'git', 'tag', '--list'
	standardOutput = code
	}
	return code.toString().split("\n").size()
	}

	curl -sSLO https://github.com/pinterest/ktlint/releases/download/0.36.0/ktlint &&
	chmod a+x ktlint &&
	sudo mv ktlint /usr/local/bin/

	./ktlint --android applyToIDEA

	# http://webapps.stackexchange.com/questions/39587/view-estimated-size-of-github-repository-before-cloning
	# tested on macOS
	echo https://github.com/torvalds/linux.git \| perl -ne 'print $1 if m!([^/]+/[^/]+?)(?:\.git)?$!' \| xargs -I{} curl -s -k https://api.github.com/repos/'{}' \| grep size

	# output:
	# "size": 1746294,

	for i in {1..141}
	do
	curl --header "Content-Type: application/json" \
	--request POST \
	--data '{"content_id":"r4xa8y35","checked_answers":"wg8sfxa2zda4","name":null}' \
	https://strawpoll.com/api/poll/vote
	done