How do I run a single command at startup using systemd?

Question

I'd like to startup an Apache Spark cluster after boot using the following command:

sudo ./path/to/spark/sbin/start-all.sh

Then run this command when the system prepares to reboot/shutdown:

sudo ./path/to/spark/sbin/stop-all.sh

How can I get started? Is there a basic template I can build on?

I've tried to use an extremely simple (file: /lib/systemd/system/spark.service):

[Unit]
Description=Spark service

[Service]
ExecStart=sudo ./path/to/spark/sbin/start-all.sh

Which doesn't work.

Answer 1

Your .service file should look like this:

[Unit]
Description=Spark service

[Service]
ExecStart=/path/to/spark/sbin/start-all.sh

[Install]
WantedBy=multi-user.target

Now, take a few more steps to enable and use the .service file:

1. Place it in /etc/systemd/system folder with a name like myfirst.service.

2. Make sure that your script is executable with:

    chmod u+x /path/to/spark/sbin/start-all.sh
   

3. Start it:

    sudo systemctl start myfirst
   

4. Enable it to run at boot:

    sudo systemctl enable myfirst
   

5. Stop it:

    sudo systemctl stop myfirst
   

Notes

1. You don't need to launch Spark with sudo in your service, as the default service user is already root.

2. Look at the links below for more systemd options.

Moreover

Now what we have above is just rudimentary, here is a complete setup for spark:

[Unit]
Description=Apache Spark Master and Slave Servers
After=network.target
After=systemd-user-sessions.service
After=network-online.target
 
[Service]
User=spark
Type=forking
ExecStart=/opt/spark-1.6.1-bin-hadoop2.6/sbin/start-all.sh
ExecStop=/opt/spark-1.6.1-bin-hadoop2.6/sbin/stop-all.sh
TimeoutSec=30
Restart=on-failure
RestartSec=30
StartLimitInterval=350
StartLimitBurst=10
 
[Install]
WantedBy=multi-user.target

To setup the service:

sudo systemctl start spark.service
sudo systemctl stop spark.service
sudo systemctl enable spark.service

Further reading

Please read through the following links. Spark is a complex setup, so you should understand how it integrates with Ubuntu's init service.

• https://datasciencenovice.wordpress.com/2016/11/30/spark-stand-alone-cluster-as-a-systemd-service-ubuntu-16-04centos-7/
• https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files
• https://www.freedesktop.org/software/systemd/man/systemd.unit.html

Answer 2

Copy-paste this into a terminal (as root) to create /root/boot.sh and run it on boot:

bootscript=/root/boot.sh
servicename=customboot

cat > $bootscript <<EOF
#!/usr/bin/env bash
echo "$bootscript ran at \$(date)!" > /tmp/it-works
EOF

chmod +x $bootscript

cat > /etc/systemd/system/$servicename.service <<EOF
[Service]
ExecStart=$bootscript
[Install]
WantedBy=default.target
EOF

systemctl enable $servicename

To modify the parameters, for example to use a different $bootscript, just set that variable manually and skip that line when copying the commands.

After running the commands, you can edit /root/boot.sh using your favorite editor, and it will run on next boot. You can also immediately run it by using:

systemctl start $servicename

Answer 3

Adding startup items in systemd is complex and cumbersome. To make this more convenient, I have wirte a tool add_service which provides a simple way to quickly add startup item in systemd.

Install:

pip3 install add_service

Usage:

python -m add_service [shell_file/cmd] [user (default `whoami`)]

Examples:

python -m add_service ssh_nat.sh  # by default user is `whoami`
python -m add_service "`which python3` -m http.server 80" root