Ab Debian Buster wird /etc/rc.local nicht mehr unterstützt und muß wie folgt einferichtet werden:

Neue Datei /etc/systemd/system/rc-local.service anlegen

[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

Neue Datei /etc/rc.local anlegen

#!/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

Script ausführbar machen

chmod +x /etc/rc.local

Service aktivieren

systemctl enable rc-local
systemctl start rc-local
systemctl status rc-local