The perils of using Wifi for Mobile Geographic Positioning

It is pretty well known that the Google StreetView cars that capture the images used for Google Street also collect information about Wifi networks in the area, to improve its location based services. In the past, Google has been known to have been collection too much information on private Wifi networks. That aside, it is a pretty cool concept- if your mobile device, such as an ipod touch, lacks GPS capabilities, it can still find where you are based on the Wifi networks around you.

The ingenuity of their system is also their crux. Take for example what I learned today. I recently made the jump to a smartphone, an HTC Evo. I LOVE the phone and 4G, one of the primary reasons I opted for the phone was for its location-based capabilities. This weekend, I am down at the family beach house enjoying a week away from work and getting in some riding/hiking/sleeping time. However I've noticed recently that when in the house, the phone's weather report is mapping Athens, GA as my current location, although I am 250+ miles south. I wrote this inaccuracy off as a glitch in Sprint's towers or something along those lines, that is until I took a closer look at Google Maps on my phone today.

I found it curious that the phone was putting me in Athens, which is where I attended the University of Georgia for four years. Out of curiosity I wanted to see where in Athens it was putting me, as I'm pretty familiar with the city and its streets. After zooming in a bit, I noticed that it was mapping me near the intersection of Baxter and Milledge ave. After zooming in all the way (which is not as far as I've been able to do when GPS is turned on), I realized where my phone was pinpointing me- off of Springdale Street, which is where I lived for two years while at the University. Sure enough, my phone was using Google's massive database of Wifi data (MAC, SSID, etc) to locate me, the same place where it had captured the router's MAC 3-4 years ago. Although the SSID of the router has changed (as well as the encryption key, etc), it is obvious that Google maps is using the MAC (media access control) address of the router as its primary identifier- it makes sense, as the primary purpose of MAC addresses is to be a unique identifier. So although I am not really near Athens at all, I am near the router that was in Athens at the time Google captured its MAC.

This presents somewhat of a quandry using Google maps. I guess Google just didn't count on people moving very often, or they figured they update their database frequently enough to mitigate this problem (note that it has been 3 years since the router as resided at that location, it has since changed geographies twice). It begs the question; is there somewhere I can go to update their database to reflect the router's new location? Also, would this occur no matter where in the world the router was located, so long as there were not any indexed networks nearby? Regardless, it is an illustrative example of how Google Maps works using Wifi data and how this clever system also has its limitations.

Gnome Wallpaper Changer

One feature I really liked about Windows 7 that is lacking on F13 Gnome is the ability to automatically rotate desktop wallpapers. This minor aesthetic functionality is easily implemented using crontab and a simple python script. I set the script to run every 15 minutes using crontab and to read from a specific folder of wallpapers (.backgrounds/dual). I used Davyd's Madeley's python script:

#!/usr/bin/python
#
# change-background.py
#
# A script to change to a random background image
#
# (c) 2004, Davyd Madeley
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
#

backgrounds = ".backgrounds/dual"

import gconf
import os
import random
import mimetypes

class GConfClient:
def __init__ (self):
self.__client__ = gconf.client_get_default ()
def get_background (self):
return self.__client__.get_string ("/desktop/gnome/background/picture_filename")
def set_background (self, background):
self.__client__.set_string ("/desktop/gnome/background/picture_filename", background)

client = GConfClient ()


dir_items = os.listdir (os.path.join (os.environ["HOME"], backgrounds))
items = []

for item in dir_items:
mimetype = mimetypes.guess_type (item)[0]
if mimetype and mimetype.split ('/')[0] == "image":
items.append (item)

item = random.randint (0, len (items) - 1)
current_bg = client.get_background ()

while (items[item] == current_bg):
item = random.randint (0, len (items) - 1)

client.set_background (os.path.join (os.environ["HOME"], backgrounds, items[item]))

The crontab file is set as:

*/15 * * * * DISPLAY=:0.0 /usr/local/bin/change-background.py

Citrix VDI

Haven't had much time to post lately as we're deep in our Citrix VDI build at work. Our lead VDI engineer left the firm about the same time our hardware arrived, which means I am not the full time engineer on the project, which I'm sincerely enjoying as it affords me the opportunity to learn and really familiarize myself with our XenDesktop 4, PVS 5.6 SP1, XenApp 6 environment. The downside is I definitely am caught spinning my wheels sometimes simply because I'm not that familiar with the technology. As a result, below is a list of a few things that I've learned thus far that is not documented on Citrix's site that may be useful for others experiencing similar issues:

1. When installing UPM on Windows XP VDIs, change the default installation location to C:\Citrix\ProfMgr. Supposedly, it can handle 8.3 filenames (filenames like C:\Prog~\Citrix\Prof), however we never got it working in our environment, even though 8.3 filenames are enabled.
2. When working on the GoldenImage or vdisk in private mode, make sure you delete all domain user profiles before XenConverting or putting the vdisk in standard mode. Otherwise UPM will complain of log file issues as it can't write to the log file because the log file is read-only, imprinted in the user profile on the vdisk, which is read-only
   
3. XenDesktop 4 does not like MS SQL 2008 SP2. While SQL 2008 is not officially supported, we've had no issues using it until SP2 was applied. Once SP2 was applied, XenDesktop continued to work, but could not reliably determine the power state of the VDIs and the XenDesktop Setup Wizard would always fail on the PVS with an error of "Invalid Host ID" when trying to create the desktop gropu
   
4. Make sure to check the "Manage Machine Account Password" on the VDisk File properties! Otherwise you'll have a nightmare of AD issues and the VDIs won't register using the Desktop Agent to the DDC
5. In a somewhat unique environment, we are required to stream to two separate VLANs. To accomplish this, we teamed two of our physical NICs on our PVS servers and trunked the teamed connection to each VLAN. This alone will not accomplish streaming to both VLANs as both the TFTP service and Provisioning Server Two Stage Boot Process only listen on one NIC by default. If you try opening the tftp.cpl control panel, it only allows you to check one adapter for the service. As for the PVS two-stage boot process control panel (.cpl), we couldn't even get it to open on our 2008 R2 Server. To allow the services to listen on all adapters, go into the registry HKLM\System\Controlset001\services\\parameters, clear the value of the "Adapter" reg key. If you run a netstat -a you'll see the service is listening on 0.0.0.0 *.*
6. Due to a client security requirement, TFTP is disallowed in the environment. As a result, we use boot ISOs to boot to our VDisks. Through trial and error, we discovered that to boot to an empy vdisk for the first time, you must use PXE boot (and subsequently, TFTP). You cannot use a boot iso when first creating a vdisk.

Off the top of my head, that's all I can think of right now. As we continue through our build phase, I will continue to supplement this list.

Helpdesk Tickets

As I may have noted in earlier posts, on my current project I split time between two roles: Citrix Virtual Desktop Engineer and Desktop Engineer, the latter essentially a glorified helpdesk technician.

On the project, we do in fact have a "helpdesk," although not in the traditional sense. Our "helpdesk" functions more as a service desk, where the helpdesk representative doesn't actually perform any troubleshooting or support duties. These "helpdesk" personnel simply take phone calls and transcribe the issue the end-user is having into our archaic and cumbersome ticketing system, and then assigns the ticket to either me or another "Desktop Engineer". Two important and relevant points follow:

a.) the helpdesk representatives don't in fact really utilize their brains. They are simply human transcribing machines. The message is spoken to the helpdesk representative, then transcribed into our ticketing system.
b.) there exists software today, and has existed for nearly a decade, that does exactly this function... better.

Here are a few tickets I've received just today; I can't decide whether it is more sad or funny. Keep in mind that the individuals authoring these tickets are grown adults that assert they are college-educated.

9/17/2010 11:02AM user name when she put in her flash drive in her computer it is not recognized it

9/17/2010 10:20AM user name he need to have his lapt top configure for wirless in the office location

9/17/2010 11:52AM user name is will be in office location the week of September 27 she was told by team lead to sey up her computer so that she can use a wireless card.

Linux Kernel Contributors

Consistent with what I found in my research for my undergraduate economics thesis, "A Theoretical Analysis of the Efficiencies of Software Development Models," virtualization.info cites Citrix and VMWare as being ranked as the #12 and #20 (respectively) contributors to the newest Linux Kernel (2.6.34). Although this may seem initially counterintuitive that two proprietary software development firms are such large contributors to open source software, it is consistent with my research findings that the largest contributors to open source software communities are in fact private, for-profit industry firms.

openSUSE on KVM

Most recent guest OS on my RHEL KVM/Qemu setup:






OpenSUSE 11.2 with KDE 4.3. Initial impression is that KDE is pretty slick, but quite different from what I'm used to, back the days of KDE 2 and 3. In terms of usability, it definitely has a learning curve. I'm definitely partial to the simple elegance of Gnome, but I intend to play a bit more with OpenSUSE and KDE.

Creating ISO images from a Directory

Recently at work, we had a need to transfer Citrix XenDesktop installation files into our VSphere 4 lab environment, however our ESX servers did not support USB, as the hypervisor did not have usb-storage.ko, uhci-hcd.ko, or ehci-hcd.ko modules compiled and we didn't have time to compile and load them into the kernel.

From our VSphere console, we can only mount ISOs and we can't drag and drop files into the VM, like in VMWare workstation, so the easiest way to get our files into our VMs was to burn an ISO. Fortunately this is pretty easy to do in Linux:

mkisofs -o files.iso -J ./folder

Credit where credit is due, this blog post was extremely helpful.