setup.sh

#!/usr/bin/env bash

PGDATA=/var/lib/postgresql/data
POSTGRES_PASSWORD=cs480
POSTGRES_USER=postgres

# used to create initial postgres directories and if run as root, ensure ownership to the "postgres" user
docker_create_db_directories() {
	local user; user="$(id -u)"

	mkdir -p "$PGDATA"
	# ignore failure since there are cases where we can't chmod (and PostgreSQL might fail later anyhow - it's picky about permissions of this directory)
	chmod 700 "$PGDATA" || :

	# ignore failure since it will be fine when using the image provided directory; see also https://github.com/docker-library/postgres/pull/289
	mkdir -p /var/run/postgresql || :
	chmod 775 /var/run/postgresql || :

	# Create the transaction log directory before initdb is run so the directory is owned by the correct user
	if [ -n "${POSTGRES_INITDB_WALDIR:-}" ]; then
		mkdir -p "$POSTGRES_INITDB_WALDIR"
		if [ "$user" = '0' ]; then
			find "$POSTGRES_INITDB_WALDIR" \! -user postgres -exec chown postgres '{}' +
		fi
		chmod 700 "$POSTGRES_INITDB_WALDIR"
	fi

	# allow the container to be started with `--user`
	if [ "$user" = '0' ]; then
		find "$PGDATA" \! -user postgres -exec chown postgres '{}' +
		find /var/run/postgresql \! -user postgres -exec chown postgres '{}' +
	fi
}

# initialize empty PGDATA directory with new database via 'initdb'
# arguments to `initdb` can be passed via POSTGRES_INITDB_ARGS or as arguments to this function
# `initdb` automatically creates the "postgres", "template0", and "template1" dbnames
# this is also where the database user is created, specified by `POSTGRES_USER` env
docker_init_database_dir() {
	# "initdb" is particular about the current user existing in "/etc/passwd", so we use "nss_wrapper" to fake that if necessary
	# see https://github.com/docker-library/postgres/pull/253, https://github.com/docker-library/postgres/issues/359, https://cwrap.org/nss_wrapper.html
	local uid; uid="$(id -u)"
	if ! getent passwd "$uid" &> /dev/null; then
		# see if we can find a suitable "libnss_wrapper.so" (https://salsa.debian.org/sssd-team/nss-wrapper/-/commit/b9925a653a54e24d09d9b498a2d913729f7abb15)
		local wrapper
		for wrapper in {/usr,}/lib{/*,}/libnss_wrapper.so; do
			if [ -s "$wrapper" ]; then
				NSS_WRAPPER_PASSWD="$(mktemp)"
				NSS_WRAPPER_GROUP="$(mktemp)"
				export LD_PRELOAD="$wrapper" NSS_WRAPPER_PASSWD NSS_WRAPPER_GROUP
				local gid; gid="$(id -g)"
				echo "postgres:x:$uid:$gid:PostgreSQL:$PGDATA:/bin/false" > "$NSS_WRAPPER_PASSWD"
				echo "postgres:x:$gid:" > "$NSS_WRAPPER_GROUP"
				break
			fi
		done
	fi

	if [ -n "${POSTGRES_INITDB_WALDIR:-}" ]; then
		set -- --waldir "$POSTGRES_INITDB_WALDIR" "$@"
	fi

	eval 'initdb --username="$POSTGRES_USER" --pwfile=<(echo "$POSTGRES_PASSWORD") '"$POSTGRES_INITDB_ARGS"' "$@"'

	# unset/cleanup "nss_wrapper" bits
	if [[ "${LD_PRELOAD:-}" == */libnss_wrapper.so ]]; then
		rm -f "$NSS_WRAPPER_PASSWD" "$NSS_WRAPPER_GROUP"
		unset LD_PRELOAD NSS_WRAPPER_PASSWD NSS_WRAPPER_GROUP
	fi
}

# append POSTGRES_HOST_AUTH_METHOD to pg_hba.conf for "host" connections
# all arguments will be passed along as arguments to `postgres` for getting the value of 'password_encryption'
pg_setup_hba_conf() {
	# default authentication method is md5 on versions before 14
	# https://www.postgresql.org/about/news/postgresql-14-released-2318/
	if [ "$1" = 'postgres' ]; then
		shift
	fi
	local auth
	# check the default/configured encryption and use that as the auth method
	auth="$(postgres -C password_encryption "$@")"
	: "${POSTGRES_HOST_AUTH_METHOD:=$auth}"
	{
		echo
		if [ 'trust' = "$POSTGRES_HOST_AUTH_METHOD" ]; then
			echo '# warning trust is enabled for all connections'
			echo '# see https://www.postgresql.org/docs/12/auth-trust.html'
		fi
		echo "host all all all $POSTGRES_HOST_AUTH_METHOD"
	} >> "$PGDATA/pg_hba.conf"
}

# start socket-only postgresql server for setting up or running scripts
# all arguments will be passed along as arguments to `postgres` (via pg_ctl)
docker_temp_server_start() {
	if [ "$1" = 'postgres' ]; then
		shift
	fi

	# internal start of server in order to allow setup using psql client
	# does not listen on external TCP/IP and waits until start finishes
	set -- "$@" -c listen_addresses='' -p "${PGPORT:-5432}"

	PGUSER="${PGUSER:-$POSTGRES_USER}" \
	pg_ctl -D "$PGDATA" \
		-o "$(printf '%q ' "$@")" \
		-w start
}

# stop postgresql server after done setting up user and running scripts
docker_temp_server_stop() {
	PGUSER="${PGUSER:-postgres}" \
	pg_ctl -D "$PGDATA" -m fast -w stop
}

# create initial database
# uses environment variables for input: POSTGRES_DB
docker_setup_db() {
	local dbAlreadyExists
	dbAlreadyExists="$(
		POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" --tuples-only <<-'EOSQL'
			SELECT 1 FROM pg_database WHERE datname = :'db' ;
		EOSQL
	)"
	if [ -z "$dbAlreadyExists" ]; then
		POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" <<-'EOSQL'
			CREATE DATABASE :"db" ;
		EOSQL
		echo
	fi
}

# check arguments for an option that would cause postgres to stop
# return true if there is one
_pg_want_help() {
	local arg
	for arg; do
		case "$arg" in
			# postgres --help | grep 'then exit'
			# leaving out -C on purpose since it always fails and is unhelpful:
			# postgres: could not access the server configuration file "/var/lib/postgresql/data/postgresql.conf": No such file or directory
			-'?'|--help|--describe-config|-V|--version)
				return 0
				;;
		esac
	done
	return 1
}

_main() {
	# setup data directories and permissions (when run as root)
	docker_create_db_directories
	if [ "$(id -u)" = '0' ]; then
		# then restart script as postgres user
		exec su-exec postgres "$BASH_SOURCE" "$@"
	fi

	# check dir permissions to reduce likelihood of half-initialized database
	ls /docker-entrypoint-initdb.d/ > /dev/null

	docker_init_database_dir
	pg_setup_hba_conf "$@"

	# PGPASSWORD is required for psql when authentication is required for 'local' connections via pg_hba.conf and is otherwise harmless
	# e.g. when '--auth=md5' or '--auth-local=md5' is used in POSTGRES_INITDB_ARGS
	export PGPASSWORD="${PGPASSWORD:-$POSTGRES_PASSWORD}"
	docker_temp_server_start "$@"

	docker_setup_db

    ## load data
    /docker-entrypoint-initdb.d/create_db.sh

	docker_temp_server_stop
	unset PGPASSWORD

	echo
	echo 'PostgreSQL init process complete; ready for start up.'
	echo
}

_main