Linux Python Raspberry Pi

What I’m working on: a Raspberry Pi digital photo frame

The idea is that for a display kiosk let’s have a Raspberry Pi drive a display like one of those electronic picture frames. Power the thing up, perhaps plug in a flash drive, leave off the mouse and keyboard, but have a display attached, and get it to where it just automatically starts a slideshow without more fuss.

Some discarded options
Obviously this is not breaking new ground. you can find many variants of this on the Internet. An early-on approach that caught my eye is flickrframe. I read the source code to learn that at the end of the day it relies on the fbi program (frame buffer imageviewer). I thought that perhaps I could rip out the part that connects to Flickr but it seemed like too much trouble. At the end of the day it’s just a question of whether to use fbi or not.

Then there’s Raspberry Pi slideshow. That’s a quite good write-up. That’s using pqiv. I think that solution is workable.

But the one I’m focusing on uses qiv. You would have thought that pqiv would rely on qiv (quick image viewer) but it appears not to. So qiv is a separate install. qiv has lots of switches so it’s been written with this kind of thing in mind it seems.

What it looks like so far

# -f : full-screen; -R : disable deletion; -s : slideshow; -d : delay <secs>; -i : status-bar;
# -m : zoom; [-r : ranomdize]
# this doesn't handle filenames with spaces:
##cd /media; qiv -f -R -s -d 5 -i -m `find /media -regex ".+\.jpe?g$"`
# this one does:
if [ "$1" = "l" ]; then
# print out proposed filenames
  cd /media; find . -regex ".+\.jpe?g$"
  sleep 5
  cd /media; find . -regex ".+\.jpe?g$" -print0|xargs -0 qiv -f -R -s -d 5 -i -m

The idea being, why not make a slideshow out of all the pictures found on a flash drive that’s been inserted into the Pi? That’s how a standard picture frame works after all. It’s a very convenient way to work with it. That’s the aim of the above script.

Requirements update
OK. Well this happens a lot in IT. We thought we were solving one problem but when we finally spoke with the visual arts team they had something entirely different in mind. They want to mix in movies as well. fbi, pqiv or qiv don’t handle movies. I have mplayer and vlc from my playing around with Raspberry Pi camera. mplayer runs like a dog on the movie files I tried, perhaps one frame update every two seconds. After more searching around I came across omxplayer. That actually works pretty well. It on the other hand doesn’t seem up to the task of handling a mixed multimedia stream of stills and movies. But it did handle the two movies types we had: .mov and .mp4 movie files. omxplayer is written specifically for the Pi so it uses its GPU for frame acceleration. mplayer just seems to rely on the CPU which just can’t keep up on a high-def quality movie. So as a result omxplayer will only play through a true graphical console. It doesn’t even bother you to get your DISPLAY environment variable set up correctly – it’s just going to send everything to the head display.

Overheard recently
And when using my TV as display omxplayer put out the sound, too, perfectly synchronized and of high quality.

I was thinking if we should kludge stitching together qiv and omxplayer. You know letting one lapse and starting up the other to transition from a still to a movie, but I don’t know how to make the transition smooth. So i searched around yet some more and found pipresents. I believe it is a python framework around omxplayer. It’s pretty sophisticated and yet free. It’s actually aimed at museums and can include reactions to pressed buttons as you have at museum displays. So far we got the example media show to loop through – it demonstrates a high-quality short movie and a still plus some captions at the beginning.

Pipresents isn’t perfect however
I quickly found some problems with pipresents so I went the official route and posted them to the github site, not really knowing what to expect. The first issue is that you are not allowed to import .mov files! That makes no sense since omxplayer plays them. So I post this bug and that very same day the author emails me back and explains that you simply edit line 32 and add .mov as an additional video file type! Sure enough, that did it. Then I found that it wasn’t downsampling my images. These days everyone has a camera or phone that takes mmulti-megapixel images far exceeding a cheap display’s 1280×1024 resolution. So you only see a small portion of your jpeg. I just assumed pipresents would downsample these large pictures because the other packages like qiv do it so readily. Again the same day the author gets back to me and says no this isn’t supported – in pipresents. But there is a solution: I should use pipresents-next! It’s officially in beta but just about ready for production release. I don’t think I’ll go that route but it’s always nice to know your package continues to be developed. I’ve written my own downsampler which I will provide later on.

Screen turns off
The pipresents has a command-line switch, -b, to prevent screen blanking. But I think in general it’s better to not use that switch and instead disable screen blanking in general.

$ sudo nano /etc/kbd/config
– change BLANK_TIME=30 to BLANK-TIME=0
$ sudo nano /etc/lightdm/lightdm.conf
– below the [SeatDefault] line create this line:
xserver-command=X -s 0 dpms

How to get started with PiPresents
$ wget -O – | tar xz

There should now be a directory ‘KenT2-pipresents-xxxx’ in your home directory. Rename the directory to pipresents:

$ mv KenT2* pipresents

To save time make sure you have two terminal windows open on your Pi and familiarize yourself with how to cut and paste text between them. Then from the one window you can:

$ cd pipresents; more

while you execute the commands you’ve cut and paste from that window into the other, e.g.,

$ sudo apt-get install python-imaging

What happens if you forget to install the unclutter package
Not much. It’s just that you will see a mouse pointer in the center of the screen which won’t go away, which is not desirable for black box operation.

Python image downsizing program
This is also known as downsampling. Amazingly, you really don’t find a simple example program like this when you do an Internet search, at least not amongst the first few hits. I needed a program to reduce the large images to the size of the display while preserving the aspect ratio. My display, a run-of-the-mill Acer v173, is 1280 x 1024 pixels. Pretty standard stuff, right? yet the Pi sees it as 1232 x 992 pixels! Whoever would have thought that possible? And with no possible option to change that (at least from the GUI). So just put in the appropriate values for your display. This program just handles one single image file. also note that if it’s a small picture, meaning smaller than the display, it will be blown up to full screen and hence will make a thumbnail image look pixelated. The match doesn’t distinguish small from large images but I fel that is fine for the most part. So without further chatting, here it is. I called it

import Image
import sys
# DrJ 2/2015
# somewhat inspired by
# image file should be provided as argument
# Designed for Acer v173 display which the Pi sees as a strange 1232 x 992 pixel display
# though it really is 1 more run-of-the-mill 1280 x 1024
imageFile = sys.argv[1]
im1 =
def imgResize(im):
# Our display as seen by the Pi is a strange 1232 x 992 pixels
    width = im.size[0]
    height = im.size[1]
# If the aspect ratio is wider than the display screen's aspect ratio,
# constrain the width to the display's full width
    if width/float(height) > 1232.0/992.0:
      widthn = 1232
      heightn = int(height*1232.0/width)
      heightn = 992
      widthn  = int(width*992.0/height)
    im5 = im.resize((widthn, heightn), Image.ANTIALIAS) # best down-sizing filter"resize/" + imageFile)

As I am not proficient in python I designed the above program to minimize file handling. That I do in a shell script which was much easier for me to write. Together they can easily handle downsampling all the image files in a particular directory. I call this script

echo "Look for the downsampled images in a sub-directory called resize
echo "JPEGs GIFs and PNGs are looked at in the current directory
mkdir resize 2>/dev/null
ls -1 *jpg *jpeg *JPG *png *PNG *gif *GIF 2>/dev/null|while read file; do
  echo downsampling $file
# downsample the image file
  python ~/ "$file"

Stopping the slideshow
Sometimes you just need to stop the thing and that’s not so easy when you’ve got it in blackbox mode and running at startup.

If you’re lucky enough to have a keyboard attached to the Pi we found that

<Alt> F4

from the keyboard stops it.

No keyboard? We assigned Our Pi a static IP address and leave an ethernet cable attached to it. Then we put a PC on the same subnet and ssh to it, e.g., using putty or teraterm. Then we run this simple kill script, which I call

pkill -f
pkill omxplayer

Digital photo frame projects morphs to museum-style kiosk display
At times I was tempted to throw out this pipresents software but we persisted. It has a different emphasis from a digital photo frame where you plug in a USB stick and don’t care about the order the pictures are presented to you. pipresents is oriented towards museums and hence is all about curated displays, where you’ve pored over the presentation order and selected your mix of videos and images. And in the end that better matched our requirements.

The manual is wanting for clarity
It’s nice that a PDF manual is included, but it’s a pain to read it to extract the small bits of information you actually need. Here’s what you mostly need to know. An unattended slideshow mixture of images and videos is what he calls a mediashow. Make your own profile to hold your mediashow:

$ cd pipresents; python

This brings up a graphical editor. Then follow these menus:

Profile|New from template|Mediashow

Choose a short easy-to-type name such as drjmedia.

Click on media.json and then you can start adding images and movies. These are known as “tracks.”

Remove the example track.

Add your own images and movies.

Do a Profile|Validate

There is no Save! Just kill it.

And to run it full screen from your home directory:

$ python pipresents/pipresents -ftop -p drjmedia

Autostarting your mediashow
The instructions provided in the manual.pdf worked on my older Pi, but not on the B+ model Pis. So to repeat it here, modifying it so that it is more correct (the author doesn’t seem comfortable with Linux). Manual.pdf has:

$ mkdir -p ~/.config/lxsession/LXDE
$ cd !$; echo "python pipresents/ -ftop -pdrjmedia" > autostart
$ chmod +x autostart

And as I say this worked on my model B Pi, but not my B+. The following discussion about autostarting programs is specific to operating systems which use the LXDE desktop environment such as Raspbian. On the B+ this fairly different approach worked to get the media show automatically starting upon boot:

$ cd /etc/xdg/autostart

Create a file pipresents.desktop with these lines:

[Desktop Entry]
Exec=python pipresents/ -ftop -pdrjmedia

But I recommend this approach which also works:

$ mkdir ~/.config/autostart

Place a pipresents.desktop file in this directory with the contents shown above.

More sophisticated approach for better black box operations
We find it convenient to run pp_editor in a virtual display created by vnc. Then we still don’t need to attach keyboard or mouse to the Pi. But the problem is that pipresents will also launch in the vnc session and really slow things down. This is a solution I worked out to have only one instance of pipresents run, even if others X sessions are launched on other displays. Note that this is a general solution and applies to any autostarted program.

The main idea is to test in a simple shell script if our display is the console (:0.0) or not.

I should interject I haven’t actually tested this but I think it’s going to work! Update: Yes, it did work!

Put in /home/pi with these contents:

# DISPLAY environment variable is :0.0 for the console display
echo $DISPLAY|grep :0 > /dev/null 2>&1
if [ "$?" == "0" ]; then
#  matched. start pipresents in this xsession, but not any other one
  python pipresents/ -ftop -pdrjmedia

Then pipresents.desktop becomes this:

[Desktop Entry]

To install the vnc server:

$ sudo apt-get install tightvncserver

And to auto-launch it make a vnc.desktop file in ~/.config/autostart like this:

[Desktop Entry]

and put this in the file /home/pi/

# DISPLAY environment variable is :0.0 for the console display
echo $DISPLAY|grep :0 > /dev/null 2>&1
if [ "$?" == "0" ]; then
#  matched. start vncserver in this xsession, but not any other one

You need to launch vncserver by hand once to establish the password.

And we may as well pre-launch the pp_editor because we’re likely to need that. So make a file in the home directory called with these contents:

# DISPLAY environment variable is :1.0 for the vnc display
echo $DISPLAY|grep :1 > /dev/null 2>&1
if [ "$?" == "0" ]; then
#  matched. start ppeditor in this xsession, but not any other one
  python pipresents/

and in ~/.config/autostart a file called ppeditor.desktop with these contents:

[Desktop Entry]

Similarly we can pre-launch an lxterminal because we’ll probably need one of those. Here’s an example

# DISPLAY environment variable is :1.0 for the vnc display
echo $DISPLAY|grep :1 > /dev/null 2>&1
if [ "$?" == "0" ]; then
#  matched. start a large lxterminal in this xsession, but not any other one
  lxterminal --geometry=100x40

and the autostart file:

[Desktop Entry]

A note about Powerpoint slides
With a Macbook we were able to read in a Powerpoint slideshow and export it to JPEG images, one image per slide. That was pretty convenient. We have done the same directly from Microsoft Powerpoint – it’s a save option.

A note about Mpeg4 videos
Some videos overwhelm these older Pis that we use. Maybe on the Pi 3 they’d be OK? A creative student would hand us his 2 minute movie in mpeg4 format. The Pi would never be able to display it. We learned you can reduce the resolution to get the Pi to display it. A student was doing this on his Macbook, but when he left i had to figure out a way.

The original mpeg4 video had resolution of 1920 x 1080. I wanted to have horizontal resolution of no more than 1232, but maybe even smaller, while preserving the aspect ratio (widescreen format).

I used good ole’ Microsoft Movie Maker. I don’t think it’s available any longer except from dodgy sites, but in the days of Windows 7 you could get it for free through Windows Live Update. Then, if you upgraded that Windows 7 PC to Windows 10, it allowed you to keep Movie Maker. That’s the only way I know of. Not that it’s a good program. It’s not. Very basic. But it does permit resizing a video stream to custom resolution, so I have to give it that. I tried various resolutions nd played them back. i finally settled on the smallest I tried: 800×450. In fact I couldn’t really tell the difference in video quality between all the samples. And of corse 800×450 made for the smallest file. So we took that one. Fortunately, pipresents blew it up to occupy the full screen width (1232 pixels) while preserving the aspect ratio. So it looks great and no further action was needed.

The sound of silence
You want the video sound to come out the stereo mini-jack because you’re not using an HDMI monitor? PiPresents tries to send audio out through HDMI by default so you won’t hear the sounds if you have a VGA monitor. But you can change that. If you want to do this in raw omxplayer the switch which sends the sound out through the mini-jack is:

omxplayer -o local

In pipresents this option is available in the pp_editor. It’s a property of the profile. So you edit the profile, look for omx-audio, and change its value in the drop-down box from hdmi to local. That’s it!

A word about DHCP
We use a PC to connect to the four Pis. They are connected to a hub and there is an Ethernet cable connected to the hub and ready to be connected to a PC with an Ethernet port. The Pis all have private IP addresses:,, and For convenience, we set up a DHCP server on Pi 1 so that when the PC connects, it gets assigned an IP address on that subnet. DHCP is a service that dynamically assigns IP addresses. Turns out this is dead easy. You simply install dnsmasq (sudo apt-get install dnsmasq) and make sure it is enabled. That’s it! More sophisticated setups require modification of the file /etc/dnsmasq.conf, but for our simple use case that is not even needed – it just picks reasonable values and assigns an appropriate IP to the laptop that allows it to communicate to any of the four Pis.

References and related
I worked on this project with a student. Building a Four Monitor Media Show using Raspberry Pis
Pipresents has its own wordpress site.

LXDE has its own official site.
Read about a first look at the custom-built 7″ Raspberry Pi touch display in this blog post.

An alternative slideshow program to pipresents is to leverage qiv. I put something together and demo it in this post, but with a twist: I pull all the photos from my own Google Drive, where I store 40,000+ pictures!

Admin Linux Network Technologies Raspberry Pi

Using your Raspberry Pi as a router

Most Raspberry Pi router HowTos describe how to make the Pi act like an Access Point. That can be very useful, and kind of tricky. Here I’ve turned wireless and wired network roles around and show how to make it route traffic from a wired LAN over its WiFi connection.

I bought the EDIMAX nano USB adapter to play around with wireless on my Pi. It wasn’t long before the network lover in me realized, Hey I got an ethernet port on one end, a wireless on the other – that sounds like a potential router – let’s have some fun! So I hooked up my cantankerous Sony Blueray player to it. The thing has always been touchy about using wireless but it also has a wired LAN connection option – in a room where I don’t have a wired ethernet network available. Enter the routing Pi…

WiFi on the Pi
There are many ways to get the thing going. The important thing to note is that this EDIMAX is tested and is known to be compatible with the Raspberry Pi. I guess they even included the appropriate driver for it, because there is no need at any time to read the mini-CD that the EDIMAX comes with and try to pull of, or worse, compile, a Linux driver like I initially feared. I think you merely need to do one of these numbers:

$ sudo apt-get update

to ensure you have the latest of everything on your Pi and that includes the driver for this WiFi adapter.

Also note that the Pi, being a tiny computer, is perfectly complemented by this nano adapter. The thing is so tiny you barely have enough surface area to pull it out of the USB slot.

As I said there are probably many ways to get your WiFi going. Being a command line lover I present that way, and even then there are alternative setups to choose from, of which I present only one here.

If you do one of these numbers:

$ cd /etc/network; sudo nano interfaces

I would recommend to add a line towards the top:

auto wlan0

and at the bottom:

# following
# to see Wifi signal strength and available signals run iwlist wlan0 scan
#allow-hotplug wlan0
iface wlan0 inet static
wpa-key_mgmt WPA-PSK

substitute the name of your WiFi SSID and the password (WPA Pre-Shared Key) in place of <MYSSID> and <MYSSIDPASSWORD>.

I prefer static IPs to dynamic ones. That way I ssh to the IP and it is the same every time.

As I am setting up a router this is not my complete interfaces file, just the part I want to emphasize for now. The complete file is listed below.

A word on what we are setting out to do – our network architecture

OK. So I am going to put the Pi next to the Blueray Player. The Pi will connect to my TP-LINK WiFi network. The Pi’s ethernet interface will connect to the LAN port on the Blueray player using a standard ethernet patch cable (these days it is not necessary to use a crossover cable as there’s always a device that auto-senses how it is wired). I will create a new network for this interface on the Pi, and make sure I’ve assigned a valid IP on this network to the Blueray player. The network I choose is – something completely different from anything I may already have in use at home.

The Blueray player can also be assigned a static IP address. I give it and the Pi I assign The gateway of the Blueray player is our routing Pi, so that makes the gateway IP

But I have another requirement: I want to conveniently put the Pi back on my wired home network in case something goes wrong with wireless. so I want to keep its valid static IP ( which it used to have when it was wired to my switch. The way to accomplish all this is to use virtual IPs on the eth0 interface. See the full /etc/network/interfaces file below which shows eht0 still assigned to IP, but as well a virtual interface eth0:0 assigned to

Convenient way to test things
Initially I was focused on the architecture I’ve outline above and getting all my interfaces up and running. And I could run, for instance,

$ sudo service networking restart

to make my changes to the interfaces file be dynamically enabled, and I can do a

$ ifconfig -a

to show all my interfaces, their IPs and other information. And I especially like

$ iwlist wlan0 scan

to show the available WiFi networks and their signal strength. But how do I know that routing is working?? Here’s how. You know the ping command, right? Normally you do

$ ping

to show you can reach the Internet. Why? because that’s a valid IP address on the Internet that responds to PING – thank you Google – and it’s easy to remember!

But since our default route is out of our WiFi-connected interface, the IP it picks for the source of that PING is the IP assigned to wlan0, namely There’s no Pi-routing involved in that so far. But now, you can choose a different source IP for your pings. So we pick our new virtual IP, like this:

$ ping -I

but instead of a nice result like

PING ( 56(84) bytes of data.
64 bytes from icmp_req=1 ttl=44 time=172 ms
64 bytes from icmp_req=2 ttl=44 time=92.7 ms
64 bytes from icmp_req=3 ttl=44 time=69.6 ms
64 bytes from icmp_req=4 ttl=44 time=70.6 ms
64 bytes from icmp_req=5 ttl=44 time=70.3 ms
64 bytes from icmp_req=6 ttl=44 time=70.5 ms
--- ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5006ms
rtt min/avg/max/mdev = 69.676/91.121/172.740/37.409 ms

we don’t get much encouragement:

PING ( from : 56(84) bytes of data.
--- ping statistics ---
4 packets transmitted, 0 received, 100% packet loss, time 3000ms

The ^C above means <CTRL-C> was typed in at the keyboard.

So we’re seeing 100% packet loss and we can safely conclude no routing is occurring. By the way, as a reality and typo check on this approach, try to specify as source your wlan0 IP, as in

$ ping -I

This should work.

Turn on routing
I feared it would be mess to get routing turned on, but it turns out to be pretty tidy, considering. Probably your Pi is already enabled for routing. Mine was. Just

$ cat /proc/sys/net/ipv4/ip_forward

and make sure the value is 1. That means it is set up to do routing. If you’re not so lucky and you have 0, enable routing:

$ sudo sysctl -w net.ipv4.ip_forward=1

But of course there’s more we have to do or else our source ping would have worked!

We need to turn on network address translation. This is the part I was worried about, never having done it before on Linux, but only with expensive products like commercial firewalls. But it’s really not bad at all.

I created a file iptables-NAT in the home directory of the pi user with these contents:

# This is a one-time script - DrJ
# 2/2014
# explained nicely in
# and seems to even work!
# flush old iptables stuff. Need to specify nat table specifically
iptables -t nat -F
iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
# make it permanent
#/usr/sbin/service iptables save
# list it
iptables -t nat -L
# persist it:
iptables-save &gt; /etc/iptables.conf
# note that in /etc/network/interfaces we added this line to read in
# iptables.conf upon reboot:
# pre-up iptables-restore &lt; /etc/iptables.conf

and ran it:

$ cd; sudo ./iptables-NAT

It outputs this:

target     prot opt source               destination
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
target     prot opt source               destination
MASQUERADE  all  --  anywhere             anywhere

Now run our source ping:

$ ping -I

PING ( from : 56(84) bytes of data.
64 bytes from icmp_req=1 ttl=44 time=76.3 ms
64 bytes from icmp_req=2 ttl=44 time=71.4 ms
--- ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 71.471/73.922/76.373/2.451 ms

Voila! It worked. We now are NATing our source address of to our wlan IP of before sending the packet along to the next router. But as skeptics, we’d like to see some more empirical proof that all that is really happening. You can. Here’s how using tcpdump.

The thing is that tcpdump doesn’t have full access to pre-processing, it only has “post processing” access. So we need to hook up the Pi to a device we are going to route traffic for, in my case the Sony Blueray player. I don’t have much control, but I can do a network diagnostics which I know tries to reach the configured DNS server (because it complained that it could not reach the DNS server during one of my early tests. So tee up tcpdump to monitor all interfaces’ traffic to like this:

$ sudo tcpdump -n -i any host

Then run ping (or a DNS query) to on that device, and voila, this is the result:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
20:22:09.041922 IP &gt; 5+ A? (36)
20:22:09.042144 IP &gt; 5+ A? (36)
20:22:09.163618 IP &gt; 5 1/0/0 A (52)
20:22:09.163777 IP &gt; 5 1/0/0 A (52)

The -i any switch told it to listen on all interfaces. Unfortunately the output doesn’t show which interface, but you can easily deduce it. the traffic comes in from my Blueray player at on eth0, and then leaves the Pi on wlan0 having had its source IP translated to And the reverse happens to the response from In fact I see from this tcpdump output that the Blueray player does not do a PING, it does an actual DNS query to Makes sense since it is a DNS server.

Be persistent
But a reboot will undo this nice NATing we have achieved. Try it. So we have to find a way to make our iptables entry persist across reboots. I’m sure there are many ways to do this. I liked this one. You add this line to the end of your interfaces file:

pre-up iptables-restore &lt; /etc/iptables.conf

And of course we already anticipated this manner of proceeding in our iptables-NAT file when we included this line at the bottom:

iptables-save &gt; /etc/iptables.conf

Now reboot again, and try that source ping as the first command you issue. Now it should work.

Ready for the real test
Now I can hook up my Blueray player with some confidence that at least the networking should be working. Assign its IP ( as mentioned above), its gateway (the Pi’s eth0:0 virtual IP, namely in our example), a DNS server (, of course!) and see if:

– we can ping from the Pi
– the Blueray player’s network tester shows OK (there aren’t many fine debugging utilities, just this single “network test”)

If the Blueray player can’t reach the configured DNS server then it its test fails.

Why this big long explanation for something that no one else in the world wants to do?
All this sounds like a very, very specific application that doesn’t apply to anyone else. But once you understand some of the core networking principles involved that I’ve touched on here, you will begin to realize that this can be very easily generalized to something much more applicable and powerful: a full-blown replacement for a standard wireless router such as my TP-LINK nano router. After all, we’ve set up almost all the utilities and facilities that you get from a standard router (NATing and routing), perhaps with one glaring exception: a DHCP service. I personally didn’t want one, but nothing prevents you from setting that up on the wired side. I give some suggestions below on how to do that in the next section.

A few words on a DHCP service
I did get that running on the Pi as well, though for an entirely different purpose. I used dnsmasq:

$ sudo apt-get install dnsmasq

and I think if you edit /etc/dnsmasq.conf and put these lines at the bottom:


I think you will pretty much have a working DHCP service as well and could use that instead of assigning static IPs.

What I fear about the DHCP service – and I think I have seen this – is that if I put the Pi back to the wired network, its DHCP server competes with the normal router’s DHCP service, and I start to lose connectivity to my devices! So be careful. If devices like your PC start to pick up 10.31.42.x addresses on a network where 192.168.2.x is expected, there could be some connectivity troubles ahead until you disconnect the Pi!

Finally, the full /etc/network/interfaces file

auto lo
auto eth0
auto eth0:0
auto wlan0
iface lo inet loopback
# DrJ change: make IP static
# somewhat inspired by - DrJ 1/8/13
#iface eth0 inet dhcp
iface eth0 inet static
# for network 3142
iface eth0:0 inet static
# following
# to see Wifi signal strength and available signals run iwlist wlan0 scan
#allow-hotplug wlan0
iface wlan0 inet static
wpa-key_mgmt WPA-PSK
# wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
#iface default inet dhcp
# to read in iptable configuration. See ~pi/iptables-NAT
# added - DrJ 3/2/14
pre-up iptables-restore &lt; /etc/iptables.conf

Yes, we got our Pi to act as a router, and it wasn’t too bad. We demonstrated it for this specific application, but also showed how the simple addition of a DHCP service would make this a very general solution.
Did it help with the problem at hand – getting smoother streaming on the Sony Blueray player? Well, actually, yes, it did seem to help.

References and related

An idea for temporarily replacing a busted home router with a Raspberry Pi router which uses your hotspot is described in this article.

Getting started on a Pi without a dedicated console is described here.
A look at playing around with real-time video using the Pi’s camera is described here.
A more esoteric project, using the Pi to monitor your home’s Internet/power connection, is presented here.
Turning your Raspberry Pi into a transparent networking bridge is described here.
Interested to run some real networking protocols on your Pi like RIP, OSPF or BGP? I suggest to look into Quagga. Quagga is a networking suite. In full disclosure I haven’t had time or motivation to experiment with it myself (yet).