Run Python code as a service

Testing of my python script that reads the serial output from MotherHub seems stable enough to run fulltime now. What I’ve found is though that everytime I turn my PC off my SSH session will time out and kill the python script from running. What I need is a way to run it all the time and auto start it after a reboot. Peiter Vanos has just the thing! I am reposting here for my own reference later. You can find the original code at

1. place your python script in the following folder: /usr/local/sbin/ (This can be anywhere you like)
2. create a new file in /etc/init.d/ in this case it will be example, so sudo nano /etc/init.d/example
3. Use the following code for the example file

#! /bin/sh
# /etc/init.d/example
case "$1" in
echo "Starting example"
# run application you want to start
python /usr/local/sbin/ &
echo "Stopping example"
# kill application you want to stop
killall python
echo "Usage: /etc/init.d/example{start|stop}"
exit 1
exit 0

4. give the file execute rights, sudo chmod 755 example
5. now execute: sudo update-rc.d example defaults

When you reboot raspbian it should automatically start the python script, else try service example start and service example stop


This worked like a charm for me. I could see SQL entries within a minute! Now to see if it can run 24/7 with no problems

Posted in Linux, Python, Raspberry Pi, SensorNet | Tagged , , | 1 Comment

none/417 4705 Squid Proxy Error

Maybe You can see a 4705 error or somewhat in your squid logs?

I just had a problem where Guncraft would tell me that it could not sync with steam and could only play in offline mode. But wait a minute… my friends can play! Sure enough a weird line in the proxy logs!  This is a Squid3 issue but we can fix it.


Add the line: 

ignore_expect_100 on

to your /etc/squid3/squid.conf file


Other apps that can have this problem:

Facebook Contact Sync

Posted in Linux | Tagged , , , , , , | Leave a comment

Looking for Wasted HD Space on the Raspberry Pi

Twice now I’ve ran out of space on my Raspberry Pi. First time I freed up some space and the second time that happened not to long after I went looking for the problem. This is how I found it…

danger@dangerpi ~ df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs          3.7G  2.9G  643M  82% /
/dev/root       3.7G  2.9G  643M  82% /
devtmpfs        180M     0  180M   0% /dev
tmpfs            38M  1.3M   37M   4% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs            75M     0   75M   0% /run/shm
/dev/mmcblk0p1   56M   20M   37M  35% /boot
tmpfs            75M     0   75M   0% /tmp
/dev/sda1       925G  898G   27G  98% /mnt/DangerDrive

rootfs and /dev/root are the same thing in this case, the RPis SDCard. The above is after I found the culprit and cleaned it out. Now lets drill into it a little more

danger@dangerpi / $ sudo du -sh *
5.2M    bin
19M     boot
0       dev
4.8M    etc
3.3M    home
50M     lib
16K     lost+found
4.0K    media
898G    mnt
36M     opt
du: cannot access `proc/12707/task/12707/fd/4': No such file or directory
du: cannot access `proc/12707/task/12707/fdinfo/4': No such file or directory
0       proc
28K     root
1.3M    run
5.9M    sbin
4.0K    selinux
4.0K    srv
0       sys
0       tmp
1.3G    usr
661M    var

Aha! We can see which folders take up all the space!

danger@dangerpi /var/log $ sudo du -sh *
0       alternatives.log
4.0K    alternatives.log.1
4.0K    alternatives.log.2.gz
4.0K    alternatives.log.3.gz
4.0K    alternatives.log.4.gz
173M    syslog.1
0       syslog.1.gz
940K    syslog.2.gz
904K    syslog.3.gz
4.0K    user.log.4.gz
8.0K    wtmp
220K    wtmp.1
12K     Xorg.0.log

I’ve cut this down a a little but look at that syslog file! Perty big for a log file. What was happening once I had a look at it was transmission which runs on this particular Pi was spamming errors about not being able to find some files. I deleted the logs taking up all the space with

sudo rm -f syslog.*

and then removed the offending files from transmission. Hopefully this proves to be the root of the problems.

Posted in Computing, Linux, Raspberry Pi | Tagged , , | 1 Comment

Transparent Squid3 Proxy Setup

You probably don’t really need a caching proxy on your home network but hey, why the hell not. You can pull some decent stats out of it over time. Most popular sites, biggest net users etc. etc. I have to admit to loving stats…. and graphs. I’m not sure of the appeal, I just like to see them. One of my all encompassing projects is to setup a sensor network around the house reporting into a MYSQL  back-end with a PHP front end serving up the graph love. But I digress! Lets setup Squid3!

This is what we need:
Spare PC
2 Network ports
Spare time



The great thing about making the Proxy transparent is there is no need to configure any browser settings! You simply send all your network traffic over the interface bridge on your proxy box and then magic kicks in! First thing we should do is get get Linux. Steep learning curve. Frustrating as hell when it doesn’t work but perseverance pays off and you will be a better person in the end. For this particular build I used Ubuntu 12.04. Once you have the image you can burn it to disk or whack it on a key. Who the hell burns DVD’s these days? Do your self a good one and chuck it on a key. There are some really great apps that can build a bootable key for you and they are free. You just point them at the ISO and away you go. I’m going to skip over the pretty standard stuff like installing Ubuntu but if you need help drop a comment and I’ll see what I can do.

So you are now looking at your new Ubuntu Desktop, Mmmm Juicy! Press the windows key and type it terminal…. now click the terminal icon. Bam! This is where we live. Make a shortcut for it on the desktop or wherever you like and fire it up.

Lets get the new install up to date

sudo apt-get update
sudo apt-get upgrade

Now lets install the stuff we will need

sudo apt-get install squid3 bridge-utils ebtables

Now we will setup Squid

sudo nano /etc/squid3/squid.conf

Change/add the appropriate lines to the below

http_port 3128 transparent
acl localnet src <strong></strong>/24
acl localhost src
http_access allow localnet
http_access allow localhost
cache_dir ufs /var/spool/squid3 5000 16 256

Please take note of the bolded IP address. Change this to suit your home network setup. Say your computer IP is… You would update the above to Press Ctrl-X, answer yes to keep changes and press enter to overwrite the current file. Now we will restart squid….

sudo /etc/init.d/squid3 restart

Now we can configure the network to pass all the data from one ethernet card to the other while redirecting port 80 (http) to port 3128(Proxy) before sending on to the interwebs.

sudo ebtables -t broute -A BROUTING -p IPv4 --ip-protocol 6 --ip-destination-port 80 -j redirect --redirect-target ACCEPT
sudo iptables -t nat -A PREROUTING -i br0 -p tcp --dport 80 -j REDIRECT --to-port 3128

We also need to enable traffic to be passed through for both IPv4 and IPv6 on your proxy PC by uncommenting the following lines in sysctl.conf.

sudo nano /etc/sysctl.conf
(remove the # to uncomment these lines)

Now to the NIC configs!

sudo nano /etc/network/interfaces
auto lo
iface lo inet loopback
auto eth1
iface eth1 inet static
auto br0
iface br0 inet static
bridge-ports eth0 eth1

Save the file and either reboot the system or just the services with:

sudo /etc/init.d/networking restart
sudo service squid3 restart

This is a good time to make sure you disconnect the cable between your router and switch. As in the top diagram you should have Router –> br01 eth1 –> Switch

Jump on the net from another pc and browse some pictures of cats. Bounce back to your proxy terminal and….

sudo tail /var/log/squid3/access.log -f

This is the live Proxy log of everything hitting your proxy. Sweet huh? Its interesting just to watch what actually goes out of your network. You may feel your eyes drawn to the screen for awhile just to watch. Maybe that’s just me though 🙂 That wasn’t so hard! All going well you’re seeing some impressive shit. All not going well you are cursing and wondering what the hell to do now. I had such problems so lets go over them. Due to me deciding to re-organize my network IPs my proxy box didnt get a DNS server to use.

sudo nano /etc/resolv.conf
nameserver <strong></strong>(Your router or DNS server)
nameserver google open DNS server)

That fixed DNS.

The other problem I had was having 2 gateways set in /etc/network/interfaces. One for each NIC. This caused two default IP routes and basically screwed me and the network for hours! You will see a rtnetlink error when trying to bring up the network interfaces if you are having much the same thing.

As I hopefully remembered to mention at the start of this post, You dont need to actually change anything on your local computers to have the traffic flow through your proxy. Wireless devices however are a little harder to deal with. The simple way is to just enter the proxy details manually on these devices. Those details being the IP of your proxy bridge interface( and the port (3128).




Posted in Linux, Networking | Tagged , , , , , , , , , , , | 6 Comments