Tested in ubuntu 16 / Varnish 4.1.9
Here a init.d script it starts a daemon per domain using varnishncsa:
#!/bin/sh
### BEGIN INIT INFO
# Provides: vhostlog
# Required-Start: $local_fs $remote_fs $network
# Required-Stop: $all
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: starts vhostlog service
# Description: starts vhostlog service
### END INIT INFO
LogsPath=/var/log/vhostlog
case "$1" in
start)
while read domain; do
varnishncsa -D -q 'ReqHeader:Host ~ "^(www\.)?'$domain'$"' \
-a -w $LogsPath/$domain-access.log \
-F '%h %l %u %t "%m %U %H" %s %b "%{Referer}i" "%{User-agent}i"'
done < /path/to/domains-list.txt
;;
stop)
killall varnishncsa
sleep 3
;;
restart)
$0 stop
$0 start
;;
*)
echo "Usage: $0 {start|stop|restart}"
exit 1
;;
esac
The content of file /path/to/domains-list.txt could be like this:
domain1.com domain2.com domain-test.org mybeautifuldomain.net
If varnish is behind another proxy (like nginx to serve SSL for example) you can change %h by %{X-Forwarded-For}i or %{X-Real-IP}i.
Once created update it in init.d:
~ $ update-rc.d vhostlog defaults
An finally start it:
~ $ /etc/init.d/vhostlog start