Why would I want to do this? For various reasons such as allow you to access information and servers that are behind a firewall, or maybe you just need to route traffic through different servers.

I’ve tested this on a 256mb Rackspace Cloud instance running Ubuntu 10.04 and with an iPhone and an iPad. Thanks to Yaniv for debugging the instructions.

Disclaimer: This is for educational uses only and I take no responsibility as to what you may do with it. The PPTP VPN setup via the instructions below has no encryption and uses the simplest and lowest form of password authentication. If you require stricter encryption and authentication methods you’ll need to read more about pptpd configuration.

Assumptions:

• The instance you are using is blank, specifically from firewall rules in iptables, otherwise, you’ll need to patch things up.
• All commands assume you are current a root user. If you logged in as root, that’s great. If not, run:
  sudo su
• Instead of messing a lot with iptables commands, I’m using ufw (Uncomplicated FireWall). In general, to most people, it will be easier to manage and work with.

Setting up the PPTP Server

In general we are going to create a PPTP VPN that is very basic without encryption and with basic authentication security (not fancy authentication protocols). Since Rackspace Cloud instance has an external interface (eth0) that has the instance public IP and an internal interface (eth1) with an internal IP used to communicate with your other Rackspace Cloud server (if you have them), we’ll create an alias network interface card that will have some other set of internal ips, which will be given to the devices connected via the VPN.

1. Install the necessary software (pptpd, pptp-linux, ppp and ufw – for firewall):
   apt-get install pptpd pptp-linux ppp ufw
2. Enable port 22 (ssh) in the firewall, so we don’t get locked out of our instance:
   ufw allow 22
3. Enable port 1723 (pptpd) in the firewall to enable access to the pptpd dameon:
   ufw allow 1723
4. Enable ufw:
   ufw enable
5. Add an aliased network interface card (eth0:0): (We use the address space of 192.168.88.0/24 since its usually free for most networks for most users. You can feel free to change this address if it is already taken)
   Edit /etc/network/interfaces:
   nano /etc/network/interfaces

   Enter the following text at the end of the file:

   auto eth0:0
   iface eth0:0 inet static
   address 192.168.88.1
   netmask 255.255.255.0
   gateway (same value as listed for eth0)
   dns-nameservers (same value as listed for eth0)

   Replace the value of “gateway” with the same value you will see in this file for “eth0″, the real public network interface.
   Replace the value of “dns-nameservers” with the same value you will see in this file for “eth0″

6. Configure the pptpd daemon:
   Edit /etc/ppp/pptpd-options:
   nano /etc/ppp/pptpd-options

   Comment out (add a “#” char at the start of the line) the following lines:
   “refuse-pap”
   “refuse-chap”
   “refuse-mschap”
   “refuse-mschap-v2″
   “require-mppe-128″

   replace “#ms-dns 10.0.0.1″ with “ms-dns 8.8.8.8″
   replace “#ms-dns 10.0.0.2″ with “ms-dns 4.4.4.4″

   The last 2 lines above sets the DNS server the devices connecting to your PPTP VPN will use. The addresses above are for the Google Public DNS server, but can be any other DNS server (including the same DNS servers as Rackspace or your hosting provider use)

   Edit /etc/pptpd.conf :

   nano /etc/pptpd.conf

   Add at the bottom of the file:

   localip 192.168.88.1
   remoteip 192.168.88.2-20

   The value of “remoteip” will be the set of IP addresses the devices connecting to the VPN will get upon successful connection. Currently, we have here 18 addresses, which is enough for 18 concurrent devices. You can make this range bigger if needed.

7. Configure the username and password that will be used to authenticate client accessing the VPN:
   Edit /etc/ppp/chap-secrets:
   nano /etc/ppp/chap-secrets
   # client server secret IP addresses
   [UserName] pptpd [Password] *

   Replace [UserName] with the username you wish to use.
   Replace [Password] with the password you wish to use (I suggest a long random password. Try this generator)

8. Enable IP forwarding in the kernel:
   Edit /etc/sysctl.conf :
   nano /etc/sysctl.conf

   Uncomment the line “net.ipv4.ip_forward=1″
   For IPv6, uncomment “net.ipv6.conf.all.forwarding=1″

9. Enable IP forwarding in ufw:
   Edit /etc/default/ufw:
   nano /etc/default/ufw

   Change the value of “DEFAULT_FORWARD_POLICY” from “DROP” to “ACCEPT”

10. Add IP masquerading rule in ufw, so that NAT will work and devices connecting to the VPN will be seen as if the traffic goes out of the VPN server:
    Edit /etc/ufw/before.rules:
    nano /etc/ufw/before.rules

    Paste the text below after the header and before the “*filter” rules:

    # nat Table rules
    *nat
    :POSTROUTING ACCEPT [0:0]

    # Allow forward traffic from eth0:0 to eth0
    -A POSTROUTING -s 192.168.88.0/24 -o eth0 -j MASQUERADE

    # don’t delete the ‘COMMIT’ line or these nat table rules won’t be processed
    COMMIT

11. Reboot the machine, cross your fingers and hope for the best :-)

Configuring your iPhone / iPad

1. In your iPhone / iPad go to “Settings” -> “General” -> “Network” -> “VPN”
   
2. Select “Add VPN Configuration”
3. Select “PPTP”
4. In “Description” enter the name of the VPN connection
5. In “Server” enter the IP address of the server (or a server name, if you mapped the server’s IP address to a domain name)
6. In “Account” enter the username you have entered into the “/etc/ppp/chap-secrets” file
7. In “Password” enter the password you entered for the above username in “/etc/ppp/chap-secrets”
8. Make sure “Send All Traffic” is turned to “ON”
9. Set “Encryption Level” to “None” (this is how we configured the PPTP server in this post, if you setup an encryption try to keep it in “Auto”
10. Select save

This will revert to use the older hashing method instead of the newer “critbit” that was first introduced in version 2.1.

You can read a little bit more about it on the Yedda Dev Blog.

At my day job we use Disco, a Python + Erlang based Map-Reduce framework, to crunch our web servers and application logs to generate useful data.

Each web server log file per day is a couple of GB of data which can amount to a lot of log data that needs to be processed on a daily.

Since the files are big it was easier for us to perform all the necessary filtering of find the rows of interest in the “map” function. The problem is, that it requires us to return some generic null value for rows that are not interesting for us. This causes the intermediate files to contains a lot of unnecessary data that has the mapping of our uninteresting rows.

To significantly reduce this number, we have started to use the “combiner” function so that our intermediate results contains an already summed up result of the file the node is currently processing that is composed only from the rows we found interesting using the filtering in the “map” phase.

For example, if we have 1,000 rows and only 200 answer a certain filtering criteria for a particular report, instead of getting 1,000 rows in the intermediate file out of which 800 have the same null value, we now get only 200 rows.

In some cases we saw an increase of up to 50% in run time (the increase in speed is the result of reducing less rows from the intermediate files), not to mention a reduction in disk space use during execution due to the smaller intermediate files.

That way, we can keep the filtering logic in the “map” function while making sure we don’t end up reducing unnecessary data.

IEs4Linux 2 is developed to be used with recent Wine versions (0.9.x). It seems that you are using an old version. It’s recommended that you update your wine to the latest version (Go to: winehq.com).

In my case it showed the above text, which seems to be a warning, and run the UI but then got stuck and didn’t complete anything.

To overcome this issue simply run the installation without the GTK based UI in a terminal window:

./ies4linux –no-gui

That’s it. Works like a charm.

When you launch your startup, your online presence (i.e. website, twitter account, facebook page, etc) and the buzz you manage to create online via the online official and unofficial press are the message you are passing to your users. If the message is not clear you can lose a lot of attention.

Before launching your startup you might want to test your messaging. I propose two very simple tests that can serve as rather good markers to determine if your message is clear.

Tests Rules:

• Each of the tests should be given to 2 different people
• These people should have no prior knowledge of your startup and what it does
• One person should be a Non-Techie – someone not from the tech industry who is known to have little to no technical background. The other should be a Techie – someone from the tech industry that can eventually ask a question along the lines of “How are you going to implement this?” and understand the answer.
• Each test should have a different set of people, you cannot reuse people from one test in the other test.

Test #1 – One sentence or less (or the 140 character pitch)

Tell each of the 2 people in one sentence or less what your startup does. If they don’t ask for additional clarification then you can consider that your message is rather clear. If they don’t ask for additional clarification, but are rather intrigued by your startup and message you can safely assume your message is clear enough and your startup does interest them.

Test #2 – The blind website test

Show your website to the 2 people without saying a word. Ask them to read what is written and explain to you what they think your startup is about. If they can explain it and understand completely what you are doing you can be certain enough that your web site message is clear even to new users who has no prior knowledge of what your startup does.

If you did not pass one of the test, try it again on a different set of people (just to make sure these 4 are not a statistical anomaly). If the result is still the same try to revise your messaging and, as always, remember to rinse and repeat.

I’m very happy to see that Google is putting their stock options and cash where their mouth is to evangelize their APIs, platforms (Android, AppEngine) and tools to developers.

A while back I wrote about the lack of Google’s outreach in the Israeli developers community, and it is still very visible in Israel by the jobs listings as well as various events and conventions that Microsoft Technology still dominates the Israeli high-tech software scene.

I do hope that hiring Don Dodge and keep on releasing tools, SDKs, Platforms and even languages such as the new Go programming language, to create the necessary diversification that every monopolized field needs.

I just hope that Google will start to do more than just very simple and shallow Dev Days in Israel and will start reaching out the community, specifically in Israel. I would like to see a Google I/O event in Israel and may be a couple of smaller events that dig down into code and details in a more intimate scenario with less people.

In general I would expect Google to start evangelizing in other countries and start having evangelists in every country they have an office. I would suggest Google to learn a bit from MSDN as well as the Microsoft Valued Professional (MVP) program – these tools are one of the best examples of creating a community based on core leaders that can drive the community as well as Google straight up.

Google is still light years from reaching the well oiled, well organized Microsoft evangelism machine and I hope Don and other will be able to make big leaps to close that gap.

After seeing Google’s new Go programming language I must say I’m excited. Not because its from Google and it got a huge buzz around the net. I am excited about the fact that people decided to think differently before they went on and created Go.

I’m reading Masterminds of Programming: Conversations with the Creators of Major Programming Languages (a good read for any programming language fanaticos) which is a set of interviews with various programming languages creators and its very interesting to see the thoughts and processes behind a couple of the most widely used programming languages (and even some non-so-widely-used programming languages).

In a recent interview Brad Fitzpatrick (of LiveJournal fame and now a Google employee) was asked:

You’ve done a lot of work in Perl, which is a pretty high-level language. How low do you think programmers need to go – do programmers still need to know assembly and how chips work?

To which he replied:

… I see people that are really smart – I would say they’re good programmers – but say they only know Java. The way they think about solving things is always within the space they know. They don’t think ends-to-ends as much. I think it’s really important to know the whole stack even if you don’t operate within the whole stack.

I subscribe to Brad’s point of view because   a) you need to know your stack from end to end – from the metals in your servers (i.e. server configuration), the operating system internals to the data structures used in your code and   b) you need to know more than one programming language to open up your mind to different ways of implementing a solution to a problem.

Perl has regular expressions baked into the language making every Perl developer to think in pattern matching when performing string operations instead of writing tedious code of finding and replacing strings. Of course you can always use various find and replace methods, but the power and way of thinking of compiled pattern matching makes it much more accessible, powerful and useful.

Python has lists and dictionaries (using a VERY efficient hashtable implementation, at least in CPython) backed into the language because lists and dictionaries are very powerful data structures that can be used in a lot solutions to problems.

One of Go’s baked in features is concurrency support in the form of goroutines. Goroutines makes the use of multi-core systems very easy without the complexities that exists in multi-processing or multi-threading programming such as synchronization. This feature actually shares some ancestry with Erlang (which by itself has a very unique syntax and vocabulary for scalable functional programming).

Every programming language brings something new to the table and a new way of looking at things and solving problems. That’s why its so special :-)

Just run the dev server under python 2.5 (i.e. python2.5 dev_appserver.py)

Windows cannot connect to the printer. Operation could not be completed (error 0x000006d1).

And you have a Samba server (version 3.0 and above) consider using the following technique to add the printer:

• Add a local printer (not a network one!)
• Select “create a new port”
• Select “Local port” as type of port
• In the port name enter the printer’s SMB path, i.e. \\sambaserver\printer_name
• Select the right driver

That’s all. Works like a charm!

If you have an older version of Samba (< 3.0) know that Vista uses NTLMv2 by default. Follow these instructions to revert back to NTLMv1 by default (also true for regular shares).

Also note that since this is a local printer that prints to a print queue on the Samba server, you might not be able to delete print jobs that were completely sent to the Samba server print queue, since we essentially created a local queue.

“Unable to retrieve MSN Address Book”

After searching a bit I found this post by Gijs Nelissen which said to use a different MSN plugin for Pidgin called msn-pecan.

I’ll reiterate the instructions for those with Ubuntu / Debian:

1. Close Pidgin (make sure the process is really down)
2. Run “apt-get install msn-pecan”
3. Start pidgin
4. Change your MSN account type from MSN to WLM
5. Reconnect

I don’t know if this error affects other libpurple based multi-headed IMs (such as Adium) (UPDATE: It appears this IS a libpurple issue – so Adium IS affected), however, the msn-pecan project has a Windows binary release as well as source release (if you care/need/want to compile it for Mac OS X or other Linux distributions).