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Raspberry Pi Chromium Kiosk Mode for Geckoboard (+ VNC)

This is just a quick brain dump for my (seemingly working) setup involving a wall-mounted screen, a Raspberry Pi, Raspbian, Chromium, and VNC with the goal of displaying a simple web site (e.g. a Geckoboard).

It’s quite simple actually. First, let’s install the necessary packages:

sudo apt-get install x11vnc vim unclutter chromium x11-xserver-utils ttf-mscorefonts-installer

Second, set up x11vnc, so you can vnc into the machine from time to time to do stuff. This can be done by creating a file called /etc/X11/Xsession.d/72x11vnc with the following contents:

#!/bin/sh
x11vnc -display :0 -forever -http -o /home/pi/x11vnc.log -loop -usepw -vencrypt only -sslonly -ssl SAVE &

In order to make all this work, also execute the following commands and follow the instructions:

sudo chmod 755 /etc/X11/Xsession.d/72x11vnc
x11vnc -sslGenCA
x11vnc -sslGenCert server
x11vnc -storepasswd

Now, you should be able to access your Raspberri Pi using a browser via https://your-ip:5900/. (A Java-based VNC viewer will open.)

Lastly, edit /etc/xdg/lxsession/LXDE/autostart and add the following:

@xset s off
@xset -dpms
@xset s noblank
@chromium -kiosk -incognito http://what-you-want-to-display/...

Also besure to to comment/remove the screensaver in that file!

That’s it. Just reboot the Pi and you should see your web site after boot.

Update: Also installing ttf-mscorefonts-installer makes Geckoboard look nicer. (Hat tip to the folks at Geckoboard!)

Send E-Mail attachments to Dropbox

At Planio and LAUNCH/CO, we receive a lot of PDF receipts for things we purchase online or services we use regularly. I want all those files to go directly into a designated folder in my Dropbox and I don’t want to look at them until the end of the month when I zip everything together and send it to our accountant.

For this purpose, I have been using a service called send to dropbox for a while until it started getting unreliable. Soon it didn’t upload any of the e-mails anymore without even supplying an error message and I ended up fiddling with my e-mail attachments by hand again. Not very funny.

So, I hacked together something that “works for me” (TM) and doesn’t rely on an external service. Well, in fact, I am still relying on Uberspace to host this, but (a) I could easily do this everywhere else and (b) it’s a huge improvement over send to dropbox which felt more like a blackbox.

This is how it’s done on Uberspace, but really the instructions are very much applicable to any Linux based setup.

Download and Setup Dropbox Uploader

Dropbox Uploader is an awesome little shell script written by Andrea Fabrizi which can be used to upload files to Dropbox from the command line. It is very handy since it has no dependencies except for curl. For my purpose, it needed a little tweaking since it would not accept files from standard input, so I forked it and am currently waiting if my pull request is being merged. I will update this article as soon as it does, since I have no interest in maintaining the fork. Andrea seems to be doing an awesome job with this.

So open a shell on your Uberspace and do the following:

mkdir -p ~/opt
cd ~/opt
git clone git://github.com/yeah/Dropbox-Uploader.git
mkdir ~/bin
ln -s ~/opt/Dropbox-Uploader/dropbox_uploader.sh ~/bin/

This installs the latest version of Dropbox Uploader in ~/opt/Dropbox-Uploader and creates a handy symlink to it in ~/bin which should be in your PATH already.

To verify if that last assumption is true (and to authenticate Dropbox Uploader), simply run

dropbox_uploader.sh

It should lead you through the process of creating your own Dropbox App and authenticating your copy of Dropbox Uploader against it. If asked for the Access Level I’d opt for App folder since this won’t give the app access to your entire Dropbox. Your credentials are stored in ~/.dropbox_uploader which is 600 by default, but if you’re a bit paranoid like me, App folder is still the safer bet.

If you’d like to test Dropbox Uploader, perform a simple upload like this:

echo "hello dropbox world?" | dropbox_uploader.sh upload - hello_world.txt

A file called hello_world.txt should magically appear in your Dropbox. Does it work? Yay! Then here comes the fun part…

Configuring qmail and reformime

Again, it should not be hard to adapt this to other MTAs, but since Uberspace uses qmail (or netqmail to be more specific) this tutorial is written for that.

At Uberspace, you get an unlimited number of e-mail addresses out of the box. Your primary is composed like this:

username@hostname.uberspace.de

Where username is your Uberspace username and hostname is the host your account is hosted on. What happens to e-mails coming this way is governed by a small file named ~/.qmail. In much the same way, you can use any e-mail address that follows this format:

username-foo@hostname.uberspace.de

Where foo can be anything you like. To specify what should happen with e-mails coming in via this address, you can create a file called ~/.qmail-foo.

So, for instance, if you want all e-mail PDF attachments sent to peter-dropbox@phoenix.uberspace.de to appear in your Dropbox, create a ~/.qmail-dropbox file with the following content:

| /usr/bin/reformime -X /bin/sh -c "if [ "\${FILENAME#*.}" == "pdf" ]; then ~/bin/dropbox_uploader.sh upload - \"\$FILENAME\";fi"

Yep. That’s one single line. It uses reformime to extract all file attachments and then uploads those that end in .pdf to your Dropbox using Dropbox Uploader.

Try it out. It should already work. There’s nothing else to do.

Update: We don’t trust Dropbox much anymore since the whole NSA stuff and the end of safe harbor agreement. The above also works great with ownCloud though, too.

VPN (IPsec) tunnel between a pfSense 2.0 router and a FRITZ!Box

We have a pfSense 2.0 router at our coworking space which is hooked up to a pretty fast VDSL line so I thought it would be a fun idea to connect my home network (where I’m using a FRITZ!Box 7390) to the work LAN using a secure and permenent VPN tunnel.

Doing a quick Google search yields results for the 1.2 version of pfSense which is outdated and does not use DynDNS hostnames for both ends, so I did a quick writeup of my own.

Prerequisites

First things first, create permanent hostnames for your pfSense and your FRITZ!Box. If your DSL provider has assigned permanent IP addresses, that’s fine. If they didn’t you’ll probably need something like DynDNS. Last time I checked, you could still get free accounts, otherwise it’s just a few bucks a year – probably a good investment. You’ll need to configure both the pfSense and the FRITZ!Box to update your DynDNS hosts whenever their IP address changes, but that’s pretty straight forward so I won’t cover it here. Fun fact: you can add CNAME records to your company domain pointing to your DynDNS host, so it looks even more professional. We use vpn.launchco.com for instance – how cool is that?

You’ll also need two different primary subnets for your networks, i.e. if your home network lives in 192.168.178.0/24, which is the standard network a FRITZ!Box uses, your work network has to use something else, like 192.168.1.0/24, which is by the way the standard that pfSense uses – so you should be safe if you’re like me a big fan of sticking with sensible vendor defaults.

Now, with the permanent hostnames and subnets in place, let’s get down to business.

Setting up pfSense

We’re using IPsec, so let’s head to VPN -> IPsec first and click the [+] icon on the bottom right to add a new phase 1 entry.

Fill the form in accordance to what you see on the following screenshot:

Screenshot of pfSense configuration phase 1 entry

Obviously, replace your-fritz.dyndns.org with the permanent hostname assigned to your FRITZ!Box as well as your-pfsense.dyndns.org with the one on your pfSense box. The Pre-Shared Key should be a long random string. Don’t worry, you won’t have to remember it. You’ll just save that in the FRITZ!Box later and then you can forget about it.

Next up, we need a phase 2 entry. For that, click the [+] icon next to a label that says Show 0 Phase-2 entries and fill the form like below:

Screenshot of pfSense configuration phase 2 entry

Here, you just need to make sure that you replace 192.168.178.0 with the actual subnet your FRITZ!Box uses. Again, if you’ve sticked with the default when setting up the box, this setting should be right for you.

That should be it for the pfSense. After saving it’ll probably ask you to apply or reload the configuration. This is safe to do now.

Setting up the FRITZ!Box

Now, let’s finish this by configuring a VPN entry in your FRITZ!Box. From my perspective, this part is much easier, because I’m just pasting code instead of fiddling with screenshots – yay!

Fire up your favorite text editor and paste the following code:

Make the necessary modifications according to the comments in the file. Then, open the FRITZ!Box configuration interface in your browser and head to Internet -> Freigaben -> VPN, use the browse button to select the file you just created and click on VPN-Einstellungen importieren.

That’s it – you’re done. In my first trials I had to go back to the pfSense interface and navigate to Status -> IPsec to click on a small [>] (“play”) button to get things rolling. Maybe you need this, maybe it just works without it.

Getting the connection up after a restart of either of the two routers sometimes fails which is most probably due to the fact that DynDNS updates have not yet propagated when the VPN tries to connect. In this case, just be patient; both boxes will keep retrying to open VPN connections and you can always stop/start on both ends yourself. Once a connection is made, the tunnels are usually stable and rock-solid. Enjoy!

Switch from Bazaar to Git

Recently I had to switch a project from Bazaar to Git. Fortunately this has become quite easy using the right plugins. Just in case anyone out there needs to do the same: these are the steps if you want to keep your version history.

Git comes with an import plugin, bzr has an export plugin available. On debian based distros you might need to install the latter using

# available in lenny-backports, squeeze and ubuntu since 9.10
sudo apt-get install bzr-fastimport

Assuming you have  Bazaar repository in the folder ./bzr-repo just follow these steps to clone it to a git repoitory in the folder ./git-repo:

BZR=./bzr-repo
GIT=./git-repo

mkdir $GIT
cd $GIT
git init
bzr fast-export ../$BZR/ | git fast-import
git checkout
cd ..

The best part is: If you missed some revisions of Bazaar, e.g. because you forgot to merge an important branch, you can easily repeat the line bzr fast-export ../$BZR/ | git fast-import and Git should be smart enough to only import missing revisions.

How to build an 8 TB RAID5 encrypted time capsule for 500 Euros

So I wanted to buy a NAS that can act as a time capsule for Apple computers and run a proper Linux at the same time. I also wanted to be able to run the occasional Windows or Linux VM and I wanted to have a lot of storage. As I knew the thing was going to be in our coworking space, it also needed to have disk encryption.

Here’s how I built this for just under €500.00 using standard components and free open source software.

Selecting the hardware components

I found the HP ProLiant MicroServer (see Review and more Picures) to deliver great value for the price. At the time of writing, you can buy it for €209.90 if you’re in Germany like me.

The N36L (which I bought) comes with a single 250GB hard drive which obviously did not meet my “a lot of storage” requirement. So I bought 4 identical Seagate Barracuda Green 2000GB SATA drives which would add another €229.92 to the bill if you bought them today. I am not an expert in hard drives, but the Seagate Barracuda brand was familiar and “Green” sounds good as well.

If you don’t want your new server to host virtual machines at some point, you can probably get out your credit card and check out right now. If you’re like me though, you’d add another 2 bars of 4GB Kingston ValueRAM PC3-10667U CL9 (DDR3-1333) to your cart. The two of them together are just €44.24, so it’s no big deal anyways.

All components together will set you off €484.06. The rest is based on open source software (Debian mostly) which is free as in beer. More about that after the break.

Continue reading →

Are you stuck in Debian/MySQL/Charset/Collation hell?

So while Debian still hasn’t changed the MySQL default caracter set and collation to utf8, we all know that the first thing to do on a vanilla Debian MySQL installation is to add the following utf8.cnf file to /etc/mysql/conf.d/:

[mysqld]
default-character-set=utf8
default-collation=utf8_unicode_ci

However, if for some reason you didn’t do that and have used software which hasn’t been consistently explicit about character sets and collations, you end up with a nice mess of character sets and collations.

There is a great post on serverfault which helps you out. It comes down to one command which will take some time based on the size of your database:

mysql -B -N --user=user --password=secret -e "SELECT DISTINCT \
CONCAT( 'ALTER TABLE \`', TABLE_SCHEMA, '\`.\`', TABLE_NAME, '\` CONVERT \
TO CHARACTER SET utf8 COLLATE utf8_unicode_ci;' ) FROM \
information_schema.COLUMNS WHERE TABLE_SCHEMA != 'information_schema';" \
| mysql --user=user --password=secret

Update:

And of course you need to alter the defaults for existing databases as well:

mysql -B -N --user=user --password=secret -e "SELECT DISTINCT \
CONCAT( 'ALTER SCHEMA \`', SCHEMA_NAME, '\` CHARACTER SET utf8 COLLATE \
utf8_unicode_ci;' ) FROM information_schema.SCHEMATA where SCHEMA_NAME \
!= 'information_schema';" | mysql --user=user --password=secret

First steps with Chef

Today, Jens and I got to play with Chef which supposedly is the hot sh$&!t when it comes to infrastructure automation and such. Installing your own Chef server seems hard at first but will work in the end.

If you’re using Debian, the APT sources will save you some headaches. Just add

deb http://apt.opscode.com/ squeeze main

to your /etc/apt/sources.list and do something like

wget -qO - http://apt.opscode.com/packages@opscode.com.gpg.key | sudo apt-key add -
sudo apt-get update

to be sure to be getting what you asked for. Then, a little sudo apt-get install chef will do the trick to set up a client and sudo apt-get install chef-server will supercharge your node with a fully blown chef server, including but not limited to CouchDB, Solr, RabbitMQ and other fancy stuff. (You’ll want to do this on two different nodes, so use Virtual Box or something.)

After you’ve set up two nodes like that, try following the rest of the instructions in this tutorial and do the first cookbook example, then you’ll have come as far as we have today.

I will update this post as we dig deeper – hopefully later this week.

Bazaar over chrooted sftp

How to set up bzr for chrooted sftp users

How to restrict a user’s access to sftp://.../var/bzr

For the prototyping editor itself and for a lot of our clients’ projects we are heavy Bazaar users at pidoco° to manage our distributed workflow. When we started some years ago we just installed bzr on one of the test servers where all of the developers had ssh access anyway. We put the repositories in /var/bzr and used sftp to checkout/push/pull source changes. This was handy as a sftp server comes with openssh installed.

As the team grew over the years we got to a point where we wanted to give new developers access to the bzr repositories without giving them full ssh access. However we did not want to have to change all the urls for existing repositories. Luckily this can be achieved easily since Debian Lenny.

Per Server Settings

On our scm server we have a user group called bzr that grants read/write access to most of the repositories (except of some personal or release branches) to all users with bzr access. And now we added the group sftponly. All users in this group will be restricted to sftp access only instead of a full shell.

sudo addgroup sftponly
sudo addgroup bzr

You probably have to add ‘/usr/lib/sftp-server’ to /etc/shells to make it a valid shell, eg. like this:

root@host # echo '/usr/lib/sftp-server' >> /etc/shells

The following settings in /etc/ssh/sshd_config force the internal sftp server to be used by openssh and change the root directory for all users in the group sftponly to /var/chroot. Make sure to restart sshd afterwards.

Subsystem sftp internal-sftp
Match Group sftponly
    ChrootDirectory /var/chroot
    AllowTCPForwarding no
    X11Forwarding no
    ForceCommand internal-sftp

Up to now our repositories have been in /var/bzr. These need to be moved to /var/chroot/var/bzr to let the sftponly users access them. /var/chroot needs to have root:root as owner for openssh to work correctly. For the existing ssh users we add a symbolic link to keep the old paths working:

sudo mkdir /var/chroot
sudo chown root:root /var/chroot
sudo mkdir /var/chroot/var
sudo mv /var/bzr /var/chroot/var
sudo ln -s /var/chroot/var/bzr /var/bzr

Per User Settings

giving the user username sftp access, but nor ssh access:

USERNAME=username                                  # give the user a name
sudo adduser ${USERNAME}                           # add user and data to system
sudo usermod -s /usr/lib/sftp-server ${USERNAME}   # disallow ssh/bash, allow ssh/ftp (sftp)
sudo adduser ${USERNAME} bzr                       # allow group access to most bzr folders
sudo adduser ${USERNAME} sftponly                  # disallow access to /, allow access to /var/bzr

This changes user’s shell to sftp-server.

Result

As a result of these settings both normal ssh users as well as restricted users in the sftponly group can use the same url for their shared repositories
bzr checkout sftp://my.domain/var/bzr/my_repository. By using chroot however users in the group sftponly are restricted to using sftp and can only access the folders in the bzr subdirectory.

Sources

In the Debian Administration Weblog you can find information on how to setup an OpenSSH SFTP chroot() with ChrootDirectory and on how to restrict users to SFTP only instead of SSH.

Where am I?

Recently I have been working for several clients where I had to test programs on different servers. The Unix prompt alone doesn’t always tell you which operating system you are logged on and – it gets worse – there seems to be no convention at all on where to store that information. Arun Singh from Novell has written a nice script to determine a Linux distro. However that script does not help you with other Unices and it isn’t installed on any server anyway. So as a note to myself here is a little collection of commands that help to find out the OS your shell is running on. A few further ideas are listed in this German linux forum.

cat /etc/issue*;
cat /etc/*-release;
cat /etc/*version;
lsb-release -a;
cat /proc/version;