This article explains how to create rc.local file in Linux Debian 9

Steps on how to add rc.local in Debian 9 can be found below.

On Debian 9, the traditional “rc.local” has been eliminated. For traditional Linux users and administrators, there is a way to get it back using SystemD. See the procedure below (NOTE: all commands must be run with root privileges):

1. Edit the non-existing file “rc-local.service” :
vi /etc/systemd/system/rc-local.service

1.1. Add the following content to “/etc/systemd/system/rc-local.service” :
[Unit]
Description=/etc/rc.local
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

2. Edit the “rc.local” file :
vi /etc/rc.local
 
2.1. Add the content below and save the file
#!/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

3. Change permissions
chmod +x /etc/rc.local

4. Enable the “rc-local” script on boot
systemctl enable rc-local

5. Start the “rc-local” script 
systemctl start rc-local.service

6. Check if any error occurred while starting the service
systemctl status rc-local.service

You may now append anything you’d like to the traditional “rc.local”. Similar procedure can be applied to Debian based distros like Ubuntu, Elementary or Kali.