Ubuntu 18.04 : how to run start up script

Add your code there:

[Unit]

Description=/etc/rc.local Compatibility

ConditionPathExists=/etc/rc.local

[Service]

Type=forking

ExecStart=/etc/rc.local start

TimeoutSec=0

StandardOutput=tty

RemainAfterExit=yes

SysVStartPriority=99

[Install]

WantedBy=multi-user.target

Create and make sure /etc/rc.local is executable and add this code inside it:

sudo chmod +x /etc/rc.local

#!/bin/sh -e

# rc.local

# This script is executed at the end of each multiuser runlevel.

# Make sure that the script will "exit 0" on success or any other

# value on error.

# In order to enable or disable this script just change the execution

# bits.

# By default this script does nothing.

exit 0

Enable the service:

1
2

sudo systemctl enable rc-local
Start service and check status:

1
2
3

sudo systemctl start rc-local.service
sudo systemctl status rc-local.service
If all goes well you can add your code to the /etc/rc.local file then restart it.