buildroot/package/postgresql/postgresql.service

[Unit]
Description=PostgreSQL database server
After=network.target

[Service]
Type=notify

# start timeout disabled because initdb may run a little
# longer (eg. 5 minutes on RaspberryPi)
TimeoutStartSec=0

User=postgres
Group=postgres

StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=postgres
PIDFile=/var/lib/pgsql/postmaster.pid

ExecStartPre=/bin/sh -c "if [ ! -f /var/lib/pgsql/PG_VERSION ]; then /usr/bin/pg_ctl initdb -D /var/lib/pgsql; fi"
ExecStart=/usr/bin/postgres -D /var/lib/pgsql
ExecReload=/usr/bin/kill -HUP $MAINPID
KillMode=mixed
KillSignal=SIGINT
TimeoutSec=0

[Install]
WantedBy=multi-user.target