DHCPv4 interfaces are no longer set by the INTERFACES variable in
/etc/default/isc-dhcp-server. Please use INTERFACESv4 instead.
Migrating automatically for now, but this will go away in the future.
Launching IPv4 server only.
Starting ISC DHCPv4 server dhcpd
dhcpd service already running (pid file /var/run/dhcpd.pid currenty exists)
Which Linux distribution are you running there?
I am guessing Debian based on the config file path. The next Webmin release will use INTERFACESv4 if defined.