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The Raspberry Pi can easily be setup as an OpenVPN server. One common feature is to access servers or services on the remote network. Another use case is to provide a secure connection when you’re not at home.

You can do this by sending all traffic over the VPN connection, instead of only traffic for the remote servers. The idea is to connect your laptop to your OpenVPN server (this is encrypted by default) and access the internet from there. Whatever you send over the wifi connection, is encrypted by the VPN and thus safe. In the comments on the previous post there was someone trying to set this up. To help him solve the issue, I tested this myself, and decided to write a post showing how to do it because I really like the idea.

This is how it looks like: you’re on a untrusted network (red) and create a safe VPN connection (green) and all traffic will flow over the green network, to the also trusted home network (lighter green). People on the red network now cannot see the sites you visit.

OpenVPN secure wifi browsing

Here’s how to set it up:

  1. Allow the OpenVPN server to route ip traffic
  2. Tell the default gw where to send traffic for OpenVPN clients
  3. Send DNS servers to the VPN Clients
  4. Configure the OpenVPN Client
  5. Test your setup

Allow the OpenVPN server to route ip traffic
First of all, you need to allow the OpenVPN server to route packets.

sudo vim /etc/sysctl.conf

Add this line, or alter it if it already exists:

net.ipv4.ip_forward = 1

Then activate the change:

sudo sysctl -p

The change is now activated, and persistent.

Tell the default gw where to send traffic for OpenVPN clients
Another important step is to tell the default gateway in the home network (lighter green) where to send traffic for theOpenVPN clients. If you omit this step, this traffic gets lost. More info in this post. Short story: add this static route to your default gateway. If it’s Linux, you’d run:

sudo route add -net gw

Assuming is the ip address of the OpenVPN server. When your router is not Linux, check the manual on howto add a static route.

Send DNS servers to the VPN clients
Most ISP’s restrict the usage of their DNS servers to their own network. When you connect to Wifi, you probably receive some DNS servers via DHCP. When you connect to VPN and then send all traffic through the VPN, you are effectively using the network (and internet connection) of your VPN server and not the local network. The DNS-servers you received via DHCP might not work because you access them from another network. To solve this, configure the OpenVPN server to push public DNS servers to use. Alternatively you can also push some local DNS servers or the DNS servers of your ISP.

sudo vim /etc/openvpn/server.conf

Add or edit these lines:

push "dhcp-option DNS"
push "dhcp-option DNS"

These are Google’s public DNS servers. Just enter some DNS servers that work on the network of your OpenVPN server and that you are allowed to use.

Configure the OpenVPN client
I’m using Viscosity and all I have to do is enable a setting to send all traffic over the VPN connection.


Alternative way: It’s also possible to configure the ‘Send all traffic over VPN connection’ on the server-side instead of the client. Both has pros and cons, of course. To set it server-side set this option in the server config:

push "redirect-gateway def1"

Test your setup
The final step: test your setup! Make sure you’re connected through some other network than the one the OpenVPN server is in. Use some public Wifi service of connect over 3G. My iPhone can share its 3G connection and start a Wifi hotspot. My MacBook connects via Wifi, then does the OpenVPN connection to the Pi. The expected behavior is then to see the public ip address of the OpenVPN server’s internet connection, instead of the 3G ip address. Use a website like to test this. Do this before connecting the VPN, and after. It should be different.

Enjoy your secure browsing experience!

Someone asked me if it were possible to download a web site and make it available offline. To some extend, this can be done. Interactive forms will not work (searching, ordering, etc), but you can use ‘wget‘ to transform a website into a static version.

It goes like this:

wget \
 --recursive \
 --no-clobber \
 --page-requisites \
 --html-extension \
 --convert-links \
 --restrict-file-names=windows \
 --domains \
 --no-parent \
 --wait=1 \
 --limit-rate=500K \

Let me explain:
The ‘–recursive’ option downloads the entire web site and ‘–domains’ tells wget not to follow links outside Otherwise you will download far too many pages. ‘–page-requisites’ makes sure we’ll get all the elements that compose the page (images, CSS, etc), ‘–html-extension’ saves files with the .html extension so they will work on a stand-alone pc, ‘–convert-links’ converts links so they’ll work off-line and ‘–no-clobber’ prevents any existing files to be overwritten

Using a ‘–limit-rate’ you can prevent wget from using all available bandwidth. Wile downloading will take longer, it is now possible to browse the web while wget is downloading.

Give it a try, it works pretty nice and is great if you’re about to make big changes to your site and you want to save a copy of the old version.

The Raspberry Pi is a $35 credit-card sized computer, with an ARM-based CPU. It uses very little power (only 3 Watt), so it’s ideal for a server that’s always-on. I was thinking what’d be a nice task for my Raspberry Pi and came up with an OpenVPN server. This enables me to connect to my home from anywhere, for example to access some files or to access the internet from there.

Before we start, Let’s have a look what’s on board the Raspberry Pi so you’ve an idea what we talk about:


Here’s mine in action:


Now, let’s see how we can turn it into a OpenVPN server. Actually this is very easy due to the fact that the Raspberry Pi is running (a modified) Debian Weezy called Raspbian. Since it’s Debian, you can use apt-get to install software:

apt-get install openvpn

After the install finishes, you need to generate keys for the server and the client(s). OpenVPN ships with the ‘easy-rsa’-tool. It’s easiest to copy the example folder and work from there.

cp -R /usr/share/doc/openvpn/examples/easy-rsa /etc/openvpn
cd /etc/openvpn/easy-rsa/2.0

The ‘easy-rsa’-tool has a file called ‘vars’ that you can edit to set some defaults. That will save you time later on but it’s not required to do so.

Load the vars like this (note the two dots):

. ./vars

Then we need to generate keys:

./build-key-server server
./build-key client-name

The first line makes sure we start from scratch. The second generates a key for the Certificate Authority. The key for the server itself is generated on the third line. Repeat the forth line for each client that needs to connect. Finally, we need the Diffie Hellman key as well, which is generated on the fifth line. Make sure you use a 2048 bit key, as suggested in the comments.

We need to copy the keys to the OpenVPN folder.

cd /etc/openvpn/easy-rsa/2.0/keys
cp ca.crt ca.key dh2048.pem server.crt server.key /etc/openvpn

Last step is to configure the server. You can copy the example config and make sure it points to the certs you just created.

cp /usr/share/doc/openvpn/examples/sample-config-files/server.conf.gz /etc/openvpn
gunzip /etc/openvpn/server.conf.gz
vim /etc/openvpn/server.conf

When you’re done, start OpenVPN like this:

/etc/init.d/openvpn start

Response looks like:

[ ok ] Starting virtual private network daemon: server.

Verify it by running:

ifconfig tun0

You’ll see:

tun0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 
 inet addr: P-t-P: Mask:
 RX packets:49 errors:0 dropped:0 overruns:0 frame:0
 TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:100 
 RX bytes:3772 (3.6 KiB) TX bytes:1212 (1.1 KiB)

Now you should be able to connect to the OpenVPN server with a client. I’m using Viscosity on Mac OSX, but there’re many clients available on almost any platform (Windows, Mac OSX, Linux). You need the client.crt, client.key and ca.crt files plus the ip-address of your Raspberry Pi.


Connecting should now work without trouble. Have a look at ‘/var/log/syslog’ to access the logfiles. You’d be able to see which client connects:

Jan 5 22:07:56 raspberrypi ovpn-server[14459]: [client-name] Peer Connection Initiated with [AF_INET]

Now that all is working, time for a last tip: when you want to access the network behind the Raspberry Pi through your OpenVPN connection, configure OpenVPN to push the right route to the clients. Edit the OpenVPN server config, and add a parameter like this:

push "route"

Be sure to enter the network- and netmask address that match your network setup. The route is automatically added on connect, and removed on disconnect.

Finally, enable routing on the Rasperry Pi:

echo 1 > /proc/sys/net/ipv4/conf/all/forwarding

Have fun with it, you can do a lot of great things with this little machine!

Update: Also see these follow-up posts that contain more detailed info on some interesting use cases and help you set it up:

HOWTO connect to hosts on a remote network using OpenVPN and some routing

Secure browsing via untrusted wifi networks using OpenVPN and the Raspberry Pi

The stats helper monkeys surprised me today with their 2012 annual report.

Here’s an excerpt:

My blog had 33,000 views in 2012. The busiest day of the year was September 4th with 644 views. The most popular post that day was How I replaced the CloudStack Virtual Router with my own physical Linux router that was featured on Linux Today.

Visitors came from 165 different countries.. wow! Most came from The United States, followed by The Netherlands and Germany. A lot of the visitors were searching on Google, some on Twitter, and found my blog that way.

Click here to see the complete report.

Thank you all and I wish you all the best in 2013!

See ya there 🙂

Now that I have some time off, I enjoy spending some of it on my blog. I played with some WordPress settings and redesigned the right column. My most important goal here is to make sharing easy.

Why? Because I benefit a lot from what others post and want to give back a bit. That’s why I write my blogs. If you find them useful, it’s now easy to share them on Twitter, Facebook, Linked-In and others. The more people benefit, the better, don’t you think?

Finally, to give my blog a personal touch, I changed the address bar to:

How do you think I can improve my blog? I appreciate your feedback 🙂

Today is a very nice day with a lot of sun shine. This morning I decided to go for a run, to get rid of the stress and to enjoy being outside. Just running for some time makes me calm and relax again. I love that feeling!

I haven’t been running for almost a year. Today I took my Garmin Forerunner 305 with me. The nice thing is that the device has a GPS chip and can track many things, like distance, pace, heartbeat, calories etc. When I got home, I uploaded the run data to the MapMyRun website. It produces these nice images:

As you’ll probably see the distance and pace are not quite impressive yet 😉 Over time it should get better.. and as long as it makes me feel good it’s ok with me!