debian bullseye enable rc.local code example
Example: debian buster enable rc.local
cat <<EOF >/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
EOF
chmod +x /etc/rc.local
systemctl daemon-reload
systemctl start rc-local
systemctl status rc-local