dunxd.com

Montessori Mashup

dunxd — Mon, 05 Mar 2012 15:22:34 +0000

From the list of Montessori Schools registered with the Montessori Schools Association and listed on the Montessori St Nicholas Charity website, with a little text processing, and the help of Google Fusion Tables, I created the below map of Montessori Schools.

Each node on the map is clickable, and provides a link to more details from the above site, as well as whether the school has acheived any accreditation from MSA.

VSAT Gotchas

dunxd — Tue, 07 Feb 2012 13:50:43 +0000

In some locations, the only option for an internet connection is to use some form of satellite link. Like any wireless medium these can be quite tricky to troubleshoot.

Here are some factors I have experienced or learnt about that can cause problems for a VSAT connection.

Obstruction to the line of sight to the satellite

Obstructive Mango Tree in Makeni, Sierra Leone

Anything that gets in between the VSAT dish and the satellite can weaken or obliterate the signal. Obviously when you initially set up a VSAT dish you find the clearest possible view of the sky, but environments have a tendancy to change. Buildings are erected, or extra floors are built. Trees grow taller or grow extra foliage. I’ve experienced this with mango trees in a couple of locations. Mango trees seem to be common in locations where VSAT is the only connection option!

RF interferance

VSAT operates in several frequency ranges, the most common being:

Ku band – 12-18 GHz
Ka band – 26.5 – 40 GHz
C Band – 4 – 8 GHz

Different things can create interference in each of these bands. Notably, WiMax operates in the 2 – 11 GHz, which overlaps C Band. C Band installations within 50 miles of a WiMax network can potentially be effected. Nice one IEEE! I have also observed local welding work to completely obliterate a Ku band signal. When the work was completed the connection came back.

Rain Fade

Ku band is notorious for being affected by water droplets in the atmosphere – commonly referred to asrain fade – although this can affect any frequency above 11 GHz. This is now usually mitigated against by changes to the transmission power at the satellite and earth stations, but can still sometimes cause problems. Build up of moisture in the feed horn of a VSAT dish can degrade the signal enough to break the connection – if the moisture is removed, or once it evaporates, the connection is reestablished.

Physical disruption

Pointing a dish at a small object 35,786 km away is a fine art. Moving the dish by just 1 degree results in pointing at something more than 600 km away from the satellite! Small knocks to the dish can result in loss of signal, but the dish still looks like it is pointing in the right direction. That is why you spend a lot of money and effort on building secure mounts for your dishes, and put up signs suggesting that getting near the dish is dangerous. Leaving dead birds lying around the dish can be helpful! Talking of birds, they have been known to build nests in VSAT dishes – they generally come with some spikes to discourage this. I’ve seen a 1.5m Maribou stork perching on a VSAT dish.

Cabling can also get damaged (and is expensive and awkward to replace). Again, investment in proper cable runs is worthwhile. Wind blowing a loose cable against a wall, especially over an edge, can result in damage to the cable.

Lightning strikes

Like any metal outdoor object pointed at the sky, lightning strikes are a risk. Generally you won’t be supplied VSAT equipment without some form of lightning protection, but adequate earthing/grounding is usually left up to you. Are lightning rods a good idea? I’m not sure, and haven’t been involved in any installations that include them.

Can you work with the Chaos Monkey?

dunxd — Fri, 25 Nov 2011 16:59:28 +0000

At the Nethope Conference, one of the better plenary sessions was by Joe Baguley of VMware. One of the things he mentioned in his talk that resonated for me was something that Netflix had developed called the Chaos Monkey.

The Chaos Monkey is a programme that Netflix run on their systems that randomly shuts down processes and services. The idea is that the world is a chaotic place, and at some point one of your processes or services will shut down. The chaos monkey simulates this, forcing everyone to design systems that can handle this or that part failing.

This seems to be a particularly important concept to grasp, particularly when building on platforms that market themselves as extremely resiliant.

At Christian Aid, I don’t think we need to build our own chaos monkeys. In our international environment, we are frequently interrupted by chaotic events, from giant signs falling on VSAT dishes (Abuja, 2008) to seemingly random VPN outages caused by ISP config errors (Port Au Prince, Dhaka, Delhi, La Paz, all to often recently). Whilst these are a proper pain in the derrier, we must learn from them, and take this learning to build more resilant infrastructure, but also organisational processes that can handle everything from Earthquakes to SAN failure taking out our email system

The Chaos Monkey teaches us to expect the unexpected.

Coding horror discussion of the Chaos Monkey
The Monkey was Apple’s invention back in the early 80s, and may have inspired Netflix engineers

Grameen’s Community Knowledge Worker programme – an I4D case study

dunxd — Fri, 25 Nov 2011 16:37:21 +0000

At this years Nethope conference, which I attended last week, the stand out for me was a presentation of a project run by Grameen – their Community Knowledge Worker programme in Uganda.

The project employs Community Knowledge Workers who live in communities in Uganda. These CKWs, many of whom were previously Agricultural Extension Workers, are “trusted neighbours” who can be consulted on a variety of issues that are deemed useful for smallholder farmers in Uganda. More details about the CKW programme can be found on the Grameen website.

At the presentation I attended, Grameen showcased the technology they are using to support their CKWs. Each CKW is supplied with an IDEOS android mobile phone – these retail for $80 in Kenya. The phones have three Grameen authored apps installed.

The first app, CKW Search, is a searchable repository of information that the CKW can consult through a very simple menu. This information is stored locally on the phone, but is updated automatically when a 3G signal is available. Each query is logged in the system with GPS coordinates, and this information is sent back to Grameen when a 3G signal is available.

The second app, CKW Survey, is a simple forms based app the CKW can use to capture images, video and text, as well as fill out surveys – typically the CKW will survey farmers who use their services. Again the data is stored locally on the phone until a 3G signal is available.

The final app, CKW Pulse, is the hub through which Grameen can communicate with the CKWs. This can be used to message an individual CKW or a group. Each CKW can monitor their own performance based on the work they have done with the other two apps. CKWs can also log support calls through CKW Pulse.

In addition to these applications, the CKWs can supplement their income by selling airtime on the phones, and selling phone charging services using the solar chargers they have for chargind the IDEOS phones.

At the backend, Grameen are using Salesforce to collect the data, and have a live dashboard where various aspects of the CKW service can be monitored. The survey application is based on the Open Data Kit – a free open-source set of tools built to make survey building and data collection quick and easy.

This project is a great showcase of what can be achieved by joining up widespread mobile phone coverage, low cost smart phones, online database systems, and a well trained local workforce.

There are a number of opportunities that Christian Aid could take advantage of here.

Simple surveys on touch screen phones are a great way to collect baseline data and aggregate it quickly, before and after other initiatives have been carried out.
The ability to collect images, audio and video and send them quickly through 3G networks means that collecting stories about our work is easier and more immediate than ever.
The Pulse application could be a useful way to immediately keep in touch with partner organisations, reminding them about deadlines, contacting them with specific messages, or allowing them to see the results of M&E activities and understand their performance.
The Search application is a simple way of making different kinds of information available offline. This could be useful for Christian Aid staff, as well as in programme work that employs the “trusted neighbour” model or similar.

For more information on the Grameen CKW project I suggest the following reading:

Grameen’s CKW project site, for general details of the CKW service
The CKW technology page, for details of the applications and backend
The CKW Dashboard
The OpenDataKit website for info on the tools used to build the CKW apps

Tip of the Day: Create your own Admin Console in MMC

dunxd — Fri, 04 Nov 2011 16:33:01 +0000

Fed up of logging on to a server as admin to manage Active Directory etc? Found that you can’t run Active Directory Users & Computers as another user?

Why not create an Admin Console that includes all the Snap Ins you use, and can be Run As an admin user during a regular session?

Here’s how.

Start > Run > mmc

MMC opens in edit mode

File > Add/Remove Snap in

Click Add button

Add the different snap ins you normally use – ADUC, DNS, Exchange, Event Log Viewer are some of mine.

Ok that, then save this MMC somewhere.

Now the tricky bit – running that MMC as a different user.

Create a shortcut to the MSC file:

Right click on the shortcut, and select Properties.

On the shortcut tab, click Advanced button.

Ok out of the shortcut properties.

Now when you double click the Shortcut it will ask you for credentials – you are in!

Note – you may need to install Admin Tools to get the different Snap Ins – see this Microsoft document on how to install different tools.

Some of the snap-ins allow you to change the context – for example Event Viewer – you can change the server it is getting the logs for. You can also set up multiple instances of some snap-ins – again, very useful if you want quick access to event logs on multiple servers.

Epping Forest Campfire

dunxd — Fri, 16 Sep 2011 21:39:00 +0000

Pretty good camp site inside the M25.

Sandpit Test

dunxd — Tue, 28 Jun 2011 22:27:00 +0000

Finally got around to moving the whole blog onto my new WordPress network, also hosting some other sites.

Delete all alerts for a user in Sharepoint with this PowerShell script

dunxd — Wed, 22 Dec 2010 10:53:09 +0000

When a user leaves an organisation, their account is usually cleaned up – either by disabling or deleting it. In Sharepoint this cleaning up is not automatic – generally Sharepoint hangs on to user accounts so that information about that user is still linked to the documents the user worked on. One of the side effects of this is that any alerts that user may have set up will remain, at least in Sharepoint 2007. This leads to a lot of undeliverable messages going to Site Administrators. Manually removing the alerts for a user requires visiting each site that has alerts, going to the site settings, User Alerts, finding the user and deleting their alerts. I wrote the following PowerShell script to remove all alerts for a given user in one step. The script requires my supporting functions script (Download SPFunctions) – you need to save this in the same directory as the script below. It works in a similar way to my Edit-SPAdmins script – it allows you to select a Web Application via GUID (don’t worry, it lists all the Web Applications and their GUIDs), and then loops through all the site collections and sites, removing the users alerts as it goes. So – on with the script (Download delete-spalert):

# Remove alerts for a given user from all SharePoint sites in a web application
# Usage:  delete-spalert.ps1  
# Example:  delete-spalert.ps1 DOMAIN\User
 
# Validate arguments
if ($args.Count -lt 1)
{
    Write-Warning "Usage: alerts.ps1 "
	Write-Warning "Username must be in DOMAIN\user format"
    exit
}
 
# check that arguement is in correct format including domain
if ($args[0] -inotmatch '^\w+[\\]\w+$')
{
    Write-Warning "Username must be in DOMAIN\User format"
    exit
}
 
# Load Sharepoint functions
.\SPFunctions.ps1;
 
# store arguement in variable
$myuser = $args[0]
 
# Preamble
cls;
write-host "###################################################################################
 
This application adds or removes alerts for a user in a specified web application
Here is a list of all Web Applications on the farm" -foregroundcolor yellow;
 
# List the GUIDs of all web apps on this farm
List-SPWebApp-GUID;
 
write-host "Please copy the GUID for the web application you wish to use by selecting then
clicking the right mouse button."  -foregroundcolor yellow;
 
write-host "
Note that the Central Admin site collection has no name,
but does have a GUID!  Don't select this one by accident!
" -foregroundcolor red;
 
Write-Host "You can paste the GUID by clicking the Right mouse button again" -ForegroundColor yellow;
# Prompt user for GUID to use
$guid = Read-Host -Prompt "GUID";
$guid = $guid.Trim();
 
# Check GUID for correct format
Write-Host "Checking GUID";
switch(Check-GUID($guid)){
	"False" { Write-Host "Error: Invalid GUID.  Exiting..." -ForegroundColor red; return;}
}
 
# Get the specified web app
$webapp = Get-SPWebApp($guid);
 
# Check that webapp has been got and if not inform user
Write-Host "The following Web App will be affected: $($webapp.name)"
Write-Host "You will be removing alerts for the following user: $myuser"
 
$continue = Read-Host -Prompt "Continue? (y|n)>";
switch($continue){
	"y" {break;}
	default {Write-Host "Exiting..." -ForegroundColor red; return;}
}
 
$alertcount = 0
 
# For each site collection remove all alerts for the given user
$time = Measure-Command {
    foreach ($site in $webapp.Sites)
    {
        # get the collection of webs
        $webs = $site.AllWebs
        foreach ($web in $webs)
        {
            # get the alerts
            $alerts = $web.Alerts
 
            # if more than 0 alerts, iterate through these alerts to see if there is one for the user
            if ($alerts.Count -gt 0)
            {
                $myalerts = @()
                $mysites += $web.Url
                foreach ($alert in $alerts)
                {
                    if ($alert.User.LoginName -eq $myuser)
                    {
                        echo "Deleting $($alert.Title)"
                        $myalerts += $alert
                        $alertcount++
                    }
                }
 
                # now we have alerts for this site, we can delete them
                foreach ($alertdel in $myalerts)
                {
                    $alerts.Delete($alertdel.ID)
                }
            }
        }
    }
}
 
echo "Deleted $alertcount alerts in $($time.TotalSeconds) seconds"

Useful coloured command prompt for Linux

dunxd — Fri, 22 Oct 2010 10:50:46 +0000

I find it useful to have a visual prompt when I am logged into a Linux server as root (something you should rarely do). One way of doing this is by adding colour to your command line prompt. I decided to colour the username green if logged in as a regular user, and red if logged in as root.

It looks like this:

[username@hostname ~]$

and when logged in as root:

[root@hostname ~]#

Here’s how to do it. While logged in as yourself, edit your .bashrc file and change the export PS1 line so it reads like this:

export PS1='[e[0;32m][u[e[m]@h W]$ '

Now su to root, and edit it’s .bashrc file changing export PS1 to this:

export PS1='[[e[0;31m]u[e[m]@h W]$ '

That easy. You can do a lot more things with your command prompt, but this is enough for me. Be careful when using non-printing characters (such as the colour commands above). These should be surrounded by escape block ([ and ]).

How the hell do Sharepoint 2007 permissions work?

dunxd — Thu, 23 Sep 2010 15:16:40 +0000

I’ve written about this before, but today I found myself explaining the whole permissioning thing to a colleague, and put together a diagram which shows how inheritance works. Permissions and groups are inherited as follows:

This shows “Administrative” rights, but can equally be applied to other permissions at any level below a site collection. Dotted boundaries show where the inheritance are optional (and shouldn’t really be called inheritance either).

To explain this a little further let’s start at the top:

Web application level

The Policy for Web Application setting allows you to give Active Directory users and groups rights over all Site Collections in that Web Application. If you give a user or group Full Access permissions at this level, they will have access to all the settings pages for all sites in the web application. These users and groups names do not show up in any Sharepoint groups or permissions pages.

Site Collection level

When creating a site collection you can set Primary and Secondary Site Collection Administrators. These can only be set as Active Directory user accounts. These users get access to all settings pages for the sites within the site collection (including the root site /). Emails sent by Sharepoint relating to sites in the site collection appear to come from the Primary Site Collection Administrator.

To update all your Site Collection Administrators in one go, take a look at my Sharepoint 2007 PowerShell scripts.

Sites

This is the level that the groups you can administer within Sharepoint become available, and what most people think of when they think of permissions in Sharepoint.

An important point to note is that there is always a root site within a site collection – this is accessed at the root of the site collection directory (/). All other sites in the site collection are subsites (or subsites of subsites) of this site. The groups and permissions you set up for this root site can be used by the other sites in the collection.

This all gets a bit complicated, so lets use an example to illustrate.

We’ve got a site collection with a root site at http://dunxd/sites/teams/. Within this site there are two subsites – a and b. Site a has a subsite 1.

When we create the site collection (and root site), Sharepoint will set up the following groups:

Teams owners – this is for users who can administer the root site. They won’t see the Site Collection admin links unless they are included in one of the higher level permissions described above.
Teams members – this is for users who need to be able to work on content in the site
Teams visitors – this is for users who only require read access to the site

When we create subsite a, we have the choice of using the same permissions as the parent site. If we choose that, subsite a will not have any additional groups created. Owners of the Teams site will also be owners of the a site, and so on.

Note that here we are simply using the groups – once these have been set up, we can change the permissions those groups have for site a without changing the permissions they have for site Teams. Also note that if we add a user to the Teams owners group, that user will also have the Owner permissions on site a.

We also have the choice of using unique permissions. If we choose that, additional groups may be created, or we may use existing groups for each of the Owner, Member and Visitor roles. The default options in this situation are to share the parent Visitors group, and create new Member and Owner groups specifically for the site.

When we come to create a subsite of site a called site 1, we get the same options for using parent permissions or unique permissions. If we use the parent permissions, we get whatever we set for the parent site – if we used the permissions for Teams in site a then site 1 will also have Teams owners as owner and so on. If we select to use unique permissions for site 1, we can create 1 Owners etc, or we can use a owners, or even Teams owners. A site can access all the groups in the parent sites above it.

This is quite a major departure from the way that normal file system permissions work. It’s also quite difficult to explain. I hope this post helps you if you need to understand this, or explain to someone else.

With any luck you didn’t need to read 800 words – the diagram explained it for you.