How to run dnscache under Upstart in Ubuntu

1. First you'll need to install djbdns package: apt-get install djbdns.
2. Create user to run dnscache: adduser --system --no-create-home dnscache
3. Create dnscache environment: dnscache-conf $(id -un) $(id -un) /tmp/dnscache (dnscache is intended to run under runit or daemontools, so environment dir is full of extra stuff which we do not need at all).
4. Copy dnscache root directory to other place: cp -a /tmp/dnscache/root /etc/dnscache.

5. Create upstart rule in file /etc/event.d/dnscache:

   description "Starts dnscache from djbdns package"
   
   start on runlevel 2
   start on runlevel 3
   
   stop on runlevel 0
   stop on runlevel 1
   stop on runlevel 4
   stop on runlevel 5
   stop on runlevel 6
   stop on shutdown
   
   respawn
   console none
   
   script
       export CACHESIZE=$((2*1024*1024))
       export DATALIMIT=$((32*1024*1024))
       export IP=127.0.0.1
       export IPSEND=0.0.0.0
       export ROOT=/etc/dnscache
       export UID=$(id -u dnscache)
       export GID=$(id -g dnscache)
       TMPFILE=$(tempfile -m0600)
       head -c128 /dev/urandom > $TMPFILE
       exec <$TMPFILE
       rm -f $TMPFILE
       exec /usr/bin/dnscache
   end script
   

6. Make sure dnscache is started: initctl list. If not, start it by running start dnscache.

7. Now you've got your own local dns cache running on 127.0.0.1.

There's a packaged version of these actions: dnscache-upstart package.