systemd unit for pgagent - linux

Question

I want to make a systemd unit for pgagnent.
I found only init.d script on this page http://technobytz.com/automatic-sql-database-backup-postgres.html, but I don't know how to exec start-stop-daemon in systemd.
I have written that unit:
[Unit]
Description=pgagent
After=network.target postgresql.service
[Service]
ExecStart=start-stop-daemon -b --start --quiet --exec pgagent --name pgagent --startas pgagent -- hostaddr=localhost port=5432 dbname=postgres user=postgres
ExecStop=start-stop-daemon --stop --quiet -n pgagent
[Install]
WantedBy=multi-user.target
But I get errors like:
[/etc/systemd/system/pgagent.service:14] Executable path is not absolute, ignoring: start-stop-daemon --stop --quiet -n pgagent
What is wrong with that unit?

Answer 1

systemd expects the ExecStart and ExecStop commands to include the full path to the executable.
start-stop-daemon is not necessary for services under systemd management. you will want to have it execute the underlying pgagent commands.
look at https://unix.stackexchange.com/questions/220362/systemd-postgresql-start-script for an example

Answer 2

If you installed pgagent with yum or apt-get, it should have created the systemd file for you. For example, on RHEL 7 (essentially CentOS 7), you can install PostgreSQL 12 followed by pgagent
sudo yum install https://download.postgresql.org/pub/repos/yum/reporpms/EL-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm
sudo yum install postgresql12
sudo yum install postgresql12-server
sudo yum install pgagent_12.x86_64
This installs PostgreSQL to /var/lib/pgsql/12 and pgagent_12 to /usr/bin/pgagent_12
In addition, it creates a systemd file at /usr/lib/systemd/system/pgagent_12.service
View the status of the service with systemctl status pgagent_12
Configure it to auto-start, then start it, with:
sudo systemctl enable pgagent_12
sudo systemctl start pgagent_12
Most likely the authentication will fail, since the default .service file has
ExecStart=/usr/bin/pgagent_12 -s ${LOGFILE} hostaddr=${DBHOST} dbname=${DBNAME} user=${DBUSER} port=${DBPORT}
Confirm with sudo tail /var/log/pgagent_12.log which will show
Sat Oct 12 19:35:47 2019 WARNING: Couldn't create the primary connection [Attempt #1]
Sat Oct 12 19:35:52 2019 WARNING: Couldn't create the primary connection [Attempt #2]
Sat Oct 12 19:35:57 2019 WARNING: Couldn't create the primary connection [Attempt #3]
Sat Oct 12 19:36:02 2019 WARNING: Couldn't create the primary connection [Attempt #4]
To fix things, we need to create a .pgpass file that is accessible when the service starts. First, stop the service
sudo systemctl stop pgagent_12
Examining the service file with less /usr/lib/systemd/system/pgagent_12.service shows it has
User=pgagent
Group=pgagent
Furthermore, /etc/pgagent/pgagent_12.conf has
DBNAME=postgres
DBUSER=postgres
DBHOST=127.0.0.1
DBPORT=5432
LOGFILE=/var/log/pgagent_12.log
Examine the /etc/passwd file to look for the pgagent user and its home directory: grep "pgagent" /etc/passwd
pgagent:x:980:977:pgAgent Job Schedule:/home/pgagent:/bin/false
Thus, we need to create a .pgpass file at /home/pgagent/.pgpass to define the postgres user's password
sudo su -
mkdir /home/pgagent
chown pgagent:pgagent /home/pgagent
chmod 0700 /home/pgagent
echo "127.0.0.1:5432:postgres:postgres:PasswordGoesHere" > /home/pgagent/.pgpass
chown pgagent:pgagent /home/pgagent/.pgpass
chmod 0600 /home/pgagent/.pgpass
The directory and file permissions are important. If you're having problems, you can enable debug logging by editing the service file at /usr/lib/systemd/system/pgagent_12.service to enable debug logging by updating the ExecStart command to have -l 2
ExecStart=/usr/bin/pgagent_12 -l 2-s ${LOGFILE} hostaddr=${DBHOST} dbname=${DBNAME} user=${DBUSER} port=${DBPORT}
After changing a .service file, things must be reloaded with sudo systemctl daemon-reload (systemd will inform you of this requirement if you forget it).
Keep starting/stopping the service and checking /var/log/pgagent_12.log Eventually, it will start properly and sudo systemctl status pgagent_12 will show
● pgagent_12.service - PgAgent for PostgreSQL 12
Loaded: loaded (/usr/lib/systemd/system/pgagent_12.service; enabled; vendor preset: disabled)
Active: active (running) since Sat 2019-10-12 20:18:18 PDT; 13s ago
Process: 6159 ExecStart=/usr/bin/pgagent_12 -s ${LOGFILE} hostaddr=${DBHOST} dbname=${DBNAME} user=${DBUSER} port=${DBPORT} (code=exited, status=0/SUCCESS)
Main PID: 6160 (pgagent_12)
Tasks: 1
Memory: 1.1M
CGroup: /system.slice/pgagent_12.service
└─6160 /usr/bin/pgagent_12 -s /var/log/pgagent_12.log hostaddr=127.0.0.1 dbname=postgres user=postgres port=5432
Oct 12 20:18:18 prismweb3 systemd[1]: Starting PgAgent for PostgreSQL 12...
Oct 12 20:18:18 prismweb3 systemd[1]: Started PgAgent for PostgreSQL 12.