$ sudo service squid3 {start|stop|restart}

To specify what to run, an upstart must have exec or script stanza. When the goal is to start two or more (multiple) instances of squid3, exec is meant to replace existing process image of /usr/sbin/squid3 executable, therefore will not start two instances.

Multiple squid3 instances started via upstart exec

As workaround we can have symbolic link to squid3 executable instead and add new upstart job configuration with exec call to the link. I need two instances running in the same machine due to the implementation design where the fist instance is HTTP proxy cache while the second one is accelerator/interceptor (reverse proxy) that serves default landing page telling user to use proxy (and how to do that). Hence, for the second instance I add:

lrwxrwxrwx 1 root root 6 May  3 09:25 /usr/sbin/squid3ins2 -> squid3
-rw-r--r-- 1 root root 1156 May  6 13:30 /etc/init/squid3ins2.conf

and for the first instance I add:

-rw-r--r-- 1 root root 298 May  3 10:13 /etc/init/squid3.override

squid3ins2 is our link and /etc/init/squid3ins2.conf contains exec call to it to run second squid3. For the first instance I choose to write an override (/etc/init/squid3.override) so that the original job configuration file is left intact. For the complete content of all files check my github v1.1 of the Squid integration. There, in details you’ll also find how both instances PID, log, etc. are differentiated by each instance config via the following directives:

http_port
cache_dir
pid_filename
cache_access_log
cache_log

• System > Preferences > Sessions
• local boot script (as services start/stop in /etc/init.d/)

I added the following shell script: setup-tap:

#! /bin/bash
tap_up() {
tunctl -t tap0 -u $USER
tunctl -t tap1 -u $USER
ifconfig tap0 192.168.20.1
ifconfig tap1 192.168.40.1
#iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
sysctl -w net.ipv4.ip_forward=1
}
tap_down() {
tunctl -d tap0
tunctl -d tap1
sysctl -w net.ipv4.ip_forward=0
}
case "$1" in
start)
tap_up
;;
stop)
tap_down
;;
*)
echo "Usage: $0 {start|stop}"
;;
esac
exit 0

Basically it is used as ./setup-tap start|stop. The following steps add it to boot:
copy it to /etc/init.d/setup-tap
chmod +xr setup-tap
update-rc.d setup-tap defaults
The last updating will put it in default runlevel:
setup-tap start in runlevel 2,3,4, and 5 setup-tap stop in runlevel 1 and 6.

Specific to this script itself, it didn’t run at first due to the $USER environment variable which must be set to arif (my username).