[GLLUG] Adding openvpn to an existing configuration

[Chris Bell]

Hello,
I have used several versions of debian, and have found that there are several 
networking and DNS resolver packages that could be used by default but 
generally do not take over if another is already running, so I end up checking 
all unless I know which is the only default. Debian version 10 "buster" 
appears to default to using systemd if it is configured, but many options could 
be automatically reset if re-booted.
I have a computer running shorewall on debian 10 "buster" using dnsmasq for 
DHCP allocation to local networks, with access to recursive resolvers via 
local networks. Dnsmasq will not start if another package has grabbed port 53. 
I tried to add openvpn but then discovered that openvpn grabs port 53 on re-
boot, and that blocks dnsmasq, so need to find a way to ensure that dnsmasq is 
started that will not be changed by any system update.
Should the symlinks from /etc/systemd/system/ be used for this, with their 
BEFORE and AFTER settings?
Thanks for any advice.
-- 
Chris Bell
Website http://chrisbell.org.uk