Jared » Technology

Bind, Resolvconf and Dynamic Updates on Ubuntu Hardy

Jared Bellows — Thu, 03 Sep 2009 05:53:47 +0000

This last week I setup a DNS server for a project at work. I have done it before but there were a couple nuances to where the zone file should be stored and how to have forwarders set by resolvconf on Hardy (8.04).

First, where to put the zone files. The default install of 8.04 has apparmor installed which restricts where the named process can write to. In the comments of /etc/apparmor.d/usr.sbin/named it notes that /var/lib/bind as the location for dynamically updated zone files. That is simple to do but is not well documented.

Lastly, using resolvconf to set the forwarders option dynamically based on the DNS servers received via DHCP. Getting this set is important as having the DNS server perform the recursive lookups on the root servers can take a long time. Being able to forward saves quite a bit of time in resolving many addresses. The first thing to do is to install resolvconf if not already installed. Once it is installed then the only thing left is to change /etc/bind/named.conf to include /var/run/bind/named.options instead of including /etc/bind/named.conf.options. The options file in /var/run/bind is actually derived from the /etc/bin/named.conf.options. That means that any options you wish to add should be placed in the /etc/bind/named.conf.options file and not in the /var/run/bin/named.options file.

This is pretty basic but documentation is very lacking. I hope in the future that better documentation is made available.

Enhancing Extract in Photoshop (Elements)

Jared Bellows — Sun, 04 Jan 2009 05:00:40 +0000

I lately have been using the Magic Extractor in Photoshop Elements 7 to extract people out of pictures for the purpose of putting a new background in place. One thing I disliked was that once I click the Okay button, all decisions were final. There was no way of going back and tweaking the extract. Everything had to be done right the first time. That is why I started doing the following so that my extraction was not on the photograph itself but was in a layer mask. This now allows me to tweak the extraction at any time.

Open the image from which you wish to extract a person or item from.
Duplicate the background layer (Layer -> Duplicate Layer).
Select the background layer.
Open the Magic Extractor (Image -> Magic Extractor).
Perform the extraction on the image.
Add a Solid Color layer below the duplicated layer (Layer -> New Fill Layer -> Solid Color).
Ctrl-Click on the thumbnail of the background layer in layer palette.
Click on the layer mask of the solid color layer.
Be sure that white is selected as the background color and black as the foreground color.
Use the Fill Bucket to paint the layer mask black.
Press the Delete key. You will now see your extracted selection in white in the layer mask thumbnail.
Delete the background layer.
Select the previously duplicated layer of your image and press Ctrl-G.

Now you have your extracted person in your working view. If you want to tweak the extraction at all, now you just need to select the layer mask and use a paint brush to work the edges. In a layer mask, black makes things become transparent and white makes them become opaque. This technique works with Photoshop as well (with some modifications to the steps).

This can also be used with selections. Instead of using the Magic Extractor, select what you want to keep and use that as the selection in the above steps.

DIY Digital Backdrops

Jared Bellows — Thu, 18 Dec 2008 21:37:10 +0000

In my November 30 – December 6, 2008 Photo of the Week, I posted a picture of my son. In that posted photo, I removed the background and placed a backdrop in place to give the appearance that the photo was taken in a studio. The backdrop is one of my own creations and in this post I will describe how I created that backdrop.

Create a new image preferably larger in resolution than the images it will be used in.
Add a layer that contains the base color for the backdrop. Think in terms of painting. We will create this base color and then “paint” patches over it.
Add a second layer with another color you want to see in the backdrop, perhaps a different shade of the base color or a completely different color.
Add a layer mask to this second layer.
Make the layer mask the item to be edited.
Use the selection tool to select a relatively small area of the layer mask. (We will be stretching this selection in following steps.)
We now need to render clouds in this selection. Most editor’s have the ability to do this. In Photoshop it is under Filters -> Render.
We now need to transform this selection to stretch it out. It needs to be stretched out to at least fill the image and perhaps stretched beyond that.
Repeats the steps of creating the second layer for any additional colors you wish to add to the backdrop.

And now you have a backdrop that can be used to add that professional touch to your home studio images. Simply copy the resulting image and paste behind your subject, or copy your subject into this image. Below is the backdrop I used for that POTW.

VServer in Xen

Jared Bellows — Mon, 14 Jan 2008 05:17:52 +0000

I had heard of it being done. I have a friend doing it. So I decided I would too. It is an interesting idea to run virtualization in virtualization. One argument I have heard for running VServer in Xen is a best of both worlds scenario. VServer uses very little resources for each virtual instance thus allowing for many, many virtual instances to be started. Xen has the ability to perform live migration. The scenario would then be that physical server A has X number of Xen virtual machines running each with Y number of VServer instances. We want to migrate one of the Xen virtual machines to physical server B for load purposes. With Xen that migration is possible and the Y number of VServer instances go with it without skipping a beat.

Xen currently ships with kernel version 2.6.18. I noticed that there was a Debian package for a Xen 2.6.22 kernel which would allow me to use the latest stable code of VServer. I downloaded that package and extracted the three patches it included for patching a vanilla 2.6.22.9 kernel for Xen. I downloaded the VServer patch for 2.6.22.10 and the vanilla kernel 2.6.22.9. I then extracted the kernel and patched it with the VServer patch. That went smooth without any “gotchas.” I then proceeded to patch the kernel with the three Xen patches from the Debian package. There were a few segments that the patch utility was unable to do automatically so I went through and performed them manually. There were relatively simple and straightforward. (Note: There was a one set of segments in ecryptfs that I did not attempt to merge.) After that I configured the kernel to include both the Xen extensions as well as the VServer extensions. Booted the new kernel and was up and running. I tested the VServer extensions by creating and starting a VServer instance running SSH. It all worked like a charm.

I am comtemplating creating a single patch of Xen and VServer for the 2.6.22.9 kernel and posting it here if for no one else but myself. Happy virtualizing.

Ubuntu/Debian Dependency Tree

Jared Bellows — Mon, 31 Dec 2007 04:17:24 +0000

The Debian package system has some pretty sweet tools written for it. I came across one of these tools that makes visualizing package depenencies possible. apt-rdepends. You can pass a list of packages to it and it will provide all the dependencies for the packages.

This is cool by itself, but apt-rdepends has an option to output the tree in dotty format. Then using dot, you can create a graphical representation of the tree. I’m included an example image of the LVS dependency tree from my custom Ubuntu image.

Using a VM to add iptables support to Windows

Jared Bellows — Thu, 30 Aug 2007 05:36:54 +0000

I began playing around with this idea after looking at how Sieve Firewall manager to achieve this. I could never understand how to use Sieve and I also wanted to add web filtering into the mix. Thus I began to develop and try this out. I started out with setting up a VM in VMware Server. I added two nics to the VM. One nic was setup to bridge with the physical nic and the other was setup on one of the unused vmnets (I used vmnet2). You need to be sure to disable the DHCP server for that network device.

From there, I followed this tutorial on freshmeat.net to setup the bridging, ebtables and iptables to setup a blind proxy. Once that was setup I disabled TCP/IP on the physical NIC. I changed the vmnet2 nic to obtain and address via DHCP. In this setup the vmnet2 will be our gateway to the internet (it obtains and IP address from the router’s DHCP server not from the VM). Since vmnet2 obtains it’s access to the internet via our VM, we can then do what we want to the traffic with iptables. In my case I wanted to redirect ports 80 and 443 to a Dansguardian/Squid proxy setup on the VM.

One catch about this method is that you’ll most likely need to have your computer behind a router. The reason for this is that your PC actually will require two IP addresses from the DCHP server. One for the VM and one for the physical PC. Many ISPs won’t hand out multiple IPs for the same household.

There is another way around that problem if you aren’t able to give your PC two IPs for whatever reason. You can setup the VM to be a NAT router instead of bridging. The Windows setup is the same. The VM will need a DHCP server and a DNS relay. It’s a little more overhead, but it’ll work. In my setup I setup iptables to send all incoming requests from outside to the physical PC so that it could be used as it was used before.

The first method I would say is the preferred method but to each their own.

Asterisk + Exchange 2007 != Unified Messaging

Jared Bellows — Fri, 03 Aug 2007 05:05:47 +0000

So, in my last post I praised Microsoft. In this one I’m going to a little bit of bashing. Hold your applause. Those familiar with Exchange know that in previous version, an Exchange Admin user could log into another mailbox via POP3 or IMAP using the Domain\Username\Mailbox Alias. I was hoping to use this to then setup a IMAP storage for voicemails in Asterisk without having to know each users password. Alas, this is not possible with Exchange 2007. I don’t understand why they removed this feature. I have suspicions that it might be related to their own Unity Messaging solution (but I think that just because it thwarted my attempts of getting some of the same functionality without using their solution).

Asterisk + sipX + Exchange 2007 Unified Messaging

Jared Bellows — Thu, 26 Jul 2007 06:29:12 +0000

Now most of the things I discuss on this blog are related to open source. I love open source but I also think that Microsoft has some amazing offerings (thank goodness comments are turned off ). Today I downloaded the Exchange 2007 virtual machine offered from Microsoft for evaluation purposes. My purpose was to try integrating Asterisk voicemail with Exchange using IMAP for unified messaging. While becoming familiar with 2007 (used 2000 and 2003 previously) I came across the Unified Messaging part of 2007. It is simply amazing. Asterisk’s voicemail is on par with it, it is the auto attendant that I can see some nice value with (if you are running an environment based on Exchange anyway). There is a how to on integrating Exchange 2007 with Asterisk. A SIP proxy is needed since Exchange 2007 only talks SIP over TCP and Asterisk only does SIP over UDP.

chan_mobile…Continued

Jared Bellows — Sun, 10 Jun 2007 06:30:34 +0000

Well, I finally got around to trying out the new chan_mobile channel for Asterisk. To start off, I’ll explain my hardware in use. My phone is a Nokia 6133. I’m using the trunk versions of Asterisk and asterisk-addons (which contains the chan_mobile module). My bluetooth “host” adaptor is a Trendnet TBW-105UB.

The first step (besides compileing Asterisk) was to pair my phone with my Asterisk server. This proved to be quite difficult. I am using Ubuntu Dapper for my OS. Here is my hcid.conf in case anyone had the same troubles I had. Once paired I started Asterisk. I used the mobile search command to find the Bluetooth Address and port for my phone. I then exited Asterisk, added my phone to mobile.conf and restarted Asterisk. Lo and behold, it worked. Asterisk was the “headset” for my phone.

My first task was to call my newly attached cell phone to see what happened. Now, when I did the install of Asterisk, I made no other changes than those changes made in mobile.conf. So when I called my cell phone, it started to ring. Asterisk then picked up and started the demo. I was unable to do much in it, because the phone I called from didn’t send the DTMF. Audio was quite good. As good as I expect from a cell phone. The next thing I tried was sending a call out through the cell phone from Asterisk. I setup a softphone on my computer, configured Asterisk to accept and then connected the softphone. I also setup an extension that would send a call out through the cell phone. The call went through and I was able to hear the other side (an IVR system). I was also able to send DTMF through. I had to push the buttons with a significant pause between numbers in order for the codes to be sent correctly (I understand that this can actually be tweaked) .

I also originated a call from the cell phone while it was connected to Asterisk. Asterisk and the phone disconnected and the call audio was directed through the cell phone’s speaker. Once the call was complete, Asterisk and the phone reconnected. I also took the phone far enough away so that it lost connection with Asterisk as to simulate taking the phone with me as I went to work, shopping or whatever. When the phone came back within range, it reconnected and Asterisk was once again in control.

I was unable to test how it would work with call waiting. I can say though that caller ID was sent through (or the number at least, but you don’t get more than that with cell phones). I can think of a couple useful reasons to connect your cell phone to Asterisk.

Time specific call screening: Use Asterisk to only allow certain numbers through when your minutes would be “Anytime” minutes and when your night and weekends started, allow all calls.

Connecting a standard phone: If you prefer to use a standard phone but only have a cell phone, you could use an ATA to connect the standard phone to Asterisk and route your calls to and from through your cell phone.

I’m sure there are other reasons to do it as well. It could be interesting in a business environment as well. One could route calls to the cellphone to the users desktop phone although this would require a small office environment.

The next thing I want to try is connecting a Bluetooth headset. This could prove to be a rather cheap method (in comparison to VoIP equipment) of connecting yourself to your Asterisk box to make those cheap long distance/international calls.

chan_mobile

Jared Bellows — Tue, 29 May 2007 06:45:03 +0000

Not quite two weeks ago a new channel type was added to asterisk-addons. This new channel is called chan_mobile. It allows a user to connect their Bluetooth enabled cellphone or headset to Asterisk. When a cellphone is connected to Asterisk, Asterisk will then handle incoming calls and can also use the cellphone to make outgoing calls. When a headset is connected, Asterisk can send calls to it and possibly originate calls.

I personally find this to be very cool. I just ordered a Bluetooth USB device so that I can try this out for myself. I’ll report back with the results in the near future, hopefully.