Added systemd unit file

Makefile

-all:
+all: postgresql-service
 	rm /etc/passwd
 	mv -v /data/etc/passwd /etc/passwd
 	rm /etc/group
@@ -35,4 +35,37 @@ all:
 	install -v -dm755 /run/postgresql
 	chown -Rv postgres:postgres /srv/pgsql /run/postgresql
 	su - postgres -c '/usr/bin/initdb -D /srv/pgsql/data'
+	@echo "d /run/postgresql 0775 postgres postgres -" > /usr/lib/tmpfiles.d/postgresql.conf
+	@echo "$$POSTGRESQL_SERVICE" > /lib/systemd/system/postgresql.service
+	systemctl enable postgresql.service
 	rm -rf postgresql-12.0
+
+postgresql-service:
+define POSTGRESQL_SERVICE
+[Unit]
+Description=PostgreSQL database server
+After=network.target
+
+[Service]
+Type=forking
+TimeoutSec=120
+User=postgres
+Group=postgres
+
+Environment=PGROOT=/srv/pgsql
+
+SyslogIdentifier=postgres
+PIDFile=/srv/pgsql/data/postmaster.pid
+
+ExecStart= /usr/bin/pg_ctl -s -D $${PGROOT}/data start -w -t 120
+ExecReload=/usr/bin/pg_ctl -s -D $${PGROOT}/data reload
+ExecStop=  /usr/bin/pg_ctl -s -D $${PGROOT}/data stop -m fast
+
+# Due to PostgreSQL's use of shared memory, OOM killer is often overzealous in
+# killing Postgres, so adjust it downward
+OOMScoreAdjust=-200
+
+[Install]
+WantedBy=multi-user.target
+endef
+export POSTGRESQL_SERVICE