After my recent switch to OS X, I fell in love with TimeMachine and the transparent backups it provides.  I even have it backing up to my Windows 7 file server wirelessly so I literally do nothing when I am at home to get seamless unattended backups (not even plugging in an external HDD).

The one issue I have found in this setup is that my VirtualBox disks (Ubuntu Linux and Windows 7) get copied completely after each backup.  This is less than ideal.  3.5GB per backup adds up very quickly!  Here I describe how I created a ‘base’ (immutable) virtual box disk and let VirtualBox create an additional differencing disk on top of the base disk.  After this, TimeMachine is only copying very small chunks of data rather than the whole 3.5GB disk!

I found quite a few posts online related to this topic, including this forum post, this forum post/tutorial about VirtualBox VDIs, this forum post, and this StackOverflow topic.  Each of these contain good information.  However, this forum post was pretty much exactly what I was looking for.

To summarize the process, we first must create the base VDI disk and mark it as immutable.  This forces VirtualBox to create a second differencing image of changes beyond the immutable base disk image.  The second step is to change the mode of the differencing disk, toggling autoreset from ON to OFF.  By default the differencing disk only applies for one run of the VM.  In otherwords, any changes across restarts will be lost.  Turning autoreset off fixes this.

Here are the steps I’ve extracted from that discussion, including commands that need to be run:

1. Create an immutable .VDI disk.
   1. Detach the base VDI from the virtual machine in the VM settings.
   2. Make the VDI immutable by running the following command:

   VBoxManage openmedium disk -type immutable DISK_FILE_NAME.vdi

   3. Reattach the now immutable VDI to the VM.
2. Tell VirtualBox to use a differencing disk explicitly. Click the check-box that says ‘Differencing Disk’ in the VBox settings for the VDI that is immutable.  Note the GUID of the differencing disk that gets created.
3. Disable autoreset for the differencing disk:
   1. By default VBox will reset the state of the machine between restarts.
   2. Disable this behavior by toggling the autoreset setting:

   VBoxManage modifyhd --autoreset off DIFFERENCING_DISK_GUID

After running through these steps you should be able to start your VM, make some changes, and restart.  The changes on disk that you made should be persistent.  It would be nice if VBox would make this particular use case all GUI-based, but at least it’s possible.  Regardless, now TimeMachine only copies the differencing disk which is significantly smaller than the base disk image.  Please let me know if this works for you in the comments!

Update (2010-5-10 21:47): If you make significant changes beyond the base disk image, it is possible for the differencing disk to grow beyond the size of the base image itself.  In this case, it may be worth it to collapse or merge the changes into the base disk image and start the differencing disk fresh.  To do this, you make a clone of the differencing disk image, use the clone as the new base, and use the process above to start fresh with a new differencing disk.  I used this forum post as a basis for this process.  The clone command is:

VBoxManage clonehd DIFFERENCING_DISK_GUID NewBaseDisk.vdi

After a few days of debating whether or not to buy a Nexus One, I finally gave in a bought one.  Rachael ended up getting a Droid Eris (Verizon) for Christmas, so in the course of a few weeks I gained access to two fantastic Android-powered phones.  I had been compiling a list of mobile application ideas and the fact that I now have the hardware to test on motivated me to start looking into Android development.

After getting the Android SDK setup I needed to connect my N1 and push an application to it for testing on real hardware.  I found some Android documentation that discussed connecting up an Android device over USB.  However, after following the steps on this page, I was still seeing strange output when running adb devices:
List of devices attached
????????????    no permissions
This led to some searching which turned up a blog post.  Basically, the Google Android team hasn’t added the Vendor ID for the Nexus One.  Apparently HTC’s USB Vendor ID isn’t correct.  So, I followed these steps to fix it:

1. Create/edit a udev rules file:
   sudo vim /etc/udev/rules.d/51-android.rules
2. Add the following line to this file:
   SUBSYSTEM=="usb", SYSFS{idVendor}=="18D1", MODE="0666"
   (Note the vendor ID of 18D1. This was changed from the HTC vendor code of 0BB4.)
3. Restart udev using either
   sudo reload udev
   or
   sudo service udev reload
4. Connect your Nexus One.
5. Run
   adb devices
   and you should see something like
   List of devices attached
############ device

Hopefully Google updates the documentation to include the Vendor ID 18D1 rather than making us hunt for this number ourselves.  Enjoy!

A few weeks ago a friend of mine gave me her dying iPod Classic.  She noted that it had started acting erratic after being dropped one too many times.  The device would skip playing parts of songs and lock up periodically.  She noted that since I’m usually one to tinker with and hack on devices, she figured I might find a good use for it–more so than she had for it at least.  Well, I’ve definitely found a good use for it by swapping out the original hard drive for flash-based solution.  The device works (nearly) like new.  Here’s how I did it.

I started the process just looking for a replacement disk.  I found various sites that sold them, but they all ranged from $120+.  I wasn’t looking to put too much money into this project.  Also, I didn’t like the idea of having a moving-parts iPod anyway since the whole reason I obtained the device in the first place was because a non-solid-state disk had been dropped one too many times while in operation.  For these reasons, I began searching for a solid-sate solution that would allow me to revive my broken iPod.

Some searching yielded the site of an interesting adapter that converts the ZIF interface of the original hard disk to one that accepts Compact Flash cards.  Additionally, the adapter was designed for exactly this purpose: converting a hard disk iPod to a solid-state device.  This was exactly what I was looking for!  After spending ~$25 on the adapter, and picking up a 32GB Kingston CF card from amazon for ~$80, I had located all the hardware I would need for the project.

Before ordering the adapter and CF card, I did want to make sure I could take the iPod apart without ruining it.  I found a few good tutorials, with the best being one at iFixIt.com.  Also, I discovered other posts about doing exactly what I wanted to do.  This site is a bit more hardcore than I was looking for (he was hand soldering connections, but the upgrades are for much older generation iPods).  I used ideas for taking apart the iPod from this post (rather than specialized tools, I used a razor blade and a few very small flat-head screw driver bits).  Using all of this, I successfully managed to take the iPod apart (without breaking anything!) and was confident I could use the hardware to complete the upgrade, so I placed the orders.

iPod, dead hard drive, ZIF to CF adapter, and 32GB CF card

Dead (dying) hard drive

iPod Classic

ZIF to CF adapter made by Tarkan Akdam (2)

ZIF to CF adapter made by Tarkan Akdam (1)

Once both the adapter and CF card had arrived, actually doing the upgrade was pretty simple.  The trickiest part of the process was actually taking apart the iPod.  The very small ribbon cables are probably the most delicate parts and getting the out of their respective connectors and putting them back in required a little patience and gentle-handedness.

Once I had inserted the CF card into the ZIF to CF adapter, I placed the adapter into the iPod housing, hooked up the various ribbon cables, and snapped the two halves of the case back together.  I connected the device up to iTunes and, after reformatting the new ~30GB volume, I had a working solid state iPod Classic!

After loading up the iPod with music and playing with it for a few weeks, I only have a few complaints.  First, the device still locks up periodically when I’m using it.  This is mostly when I first start playing a new set of songs.  I suspect that this is due to the slower CF card that I picked up.  Second, the CF card is only 32GB, so I can’t fit all of my music on it.  However, I think in time CF card prices will come down and I’ll be able to swap the current card out with a 64GB or 128GB card.  Other than these two complaints, I’m very happy with this hack.  I ended up with a 32GB flash-based iPod classic for ~$100.  Check out the full set of pictures below.

Following the instructions on this site, I created a new file (/etc/hal/fdi/policy/mouse-wheel.fdi) as root that contains:

<match key="info.product" string="TPPS/2 IBM TrackPoint">
<merge key="input.x11_options.EmulateWheel" type="string">true</merge>
<merge key="input.x11_options.EmulateWheelButton" type="string">2</merge>
<merge key="input.x11_options.XAxisMapping" type="string">6 7</merge>
<merge key="input.x11_options.YAxisMapping" type="string">4 5</merge>
<merge key="input.x11_options.ZAxisMapping" type="string">4 5</merge>
<merge key="input.x11_options.Emulate3Buttons" type="string">true</merge>
</match>

If you don’t want to restart, you can log out and restart the gdm and hal services.  However, I simply restarted and scrolling worked upon logging in!

The document here is apparently the original source of this information.  I’m mostly posting this for myself for future reference (and in case either of the afore mentioned pages go down).

Waf is a Python based build system (or more generally a task execution system).  Directly from the site:

Waf is a Python-based framework for configuring, compiling and installing applications. It derives from the concepts of other build tools such as Scons, Autotools, CMake or Ant.

Just like make, waf is a quasi-declarative build system.  You define the tasks and results you require, and waf determines dependences and executes the tasks (in a valid order) necessary to produce the desired output.  However, waf differs from make in that waf actually uses a real programming language for declaring tasks and developing the build system (in case it wasn’t obvious, the language I’m referring to is Python).  This single fact alone is enough for me to want to move away from make completely.  However, waf also offers a whole slew of other extremely nice features that make it very powerful. See the project site for more details.

Until now I’ve been using make to build my LaTeX documents.  However, I’ve finally taken the time to discover how to do this with waf.  The following script (really just two functions), named wscript in the directory with the LaTeX source, is the result:

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srcdir='.'
blddir='build'
 
def configure(conf):
   conf.check_tool('tex')
 
def build(bld):
   obj=bld.new_task_gen(features='tex')
   obj.source='source_tex_file.tex'
   bld.install_files('${PREFIX}','output_pdf_file.pdf')

The first two lines define the source directory (the current directory is denoted by the ‘.’) and the name of the build directory (where all the temporary files will be stored).  The configure function simply tells waf, using the check_tool call, to ensure that the tools necessary for building LaTeX documents are present on the system.  The build function defines that we want to create a PDF document from the file source_tex_file.tex using the tex waf tool.  And that’s it… seriously.

My workflow with this setup is basically edit LaTeX file, call ./waf build install, check the output PDF, repeat.  Easy as pie.

So, if you’re looking for a fabulous alternative to make, check out waf, I’m sure you’ll be impressed.

I found this bug and this discussion of why NoDisplay is set to true.

Update (2009-9-27 19:13): After waiting for a while to see if evince would ever show up in the menus/gnome-do, it appears that this ‘fix’ doesn’t work.  I’m not willing to put more time into this, so my current work-around is to open a directory with the pdf of interest and open the file that way.  Not my preferred workflow, but it gets the job done.

Update (2009-10-7 08:46): A commenter suggested removing the NoDisplay line altogether.  I’ve commented these lines out in the files /usr/share/applications/evince.desktop and /usr/share/app-install/desktop/evince.desktop. I’ll leave it like that and see if an entry for Evince shows up anwhere. I’ve actually gotten into the habbit of opening a directory in Nautilus and opening the document in question from there. If this works though, I’ll have multiple ways of doing what I want.

Update (2009-10-10 07:34): Removing the lines didn’t help. Looks like I’ll just continue using the ‘Open in Nautilus’ method.

The (hopefully) last major remaining problem I managed to solve last night.  I’ve been watching the 5th season of Lost (after getting it playing using Shark007′s Codec Pack).  These were 720p HD H264 mkvs and played fine.  However, another set of videos encoded with Xvid and refused to play in Media Center but would play in Media Player.

Media Center’s error was: Cannot Play Video: Windows Media Center cannot open the file.  Wow, such a descriptive error message.

I tried searching for logs to see if I could get more information about the error, but had no luck with this.

I tried all sorts of configuration utilities but nothing seemed to work.

I finally stumbled upon an article on the Hack Windows 7 Media Center site that talks about the Media Center Decoder Utility (MCDU).  This tool lets one select the default audio and video decoders.  When I ran it, there was apparently no default audio decoder selected.  I selected ‘Microsoft DTV-DVD’ as the default for for both audio and video.  After clicking ‘Set Defaults’ and restarting Media Center,

Note: I had previously followed another Hack7MC article that had me ‘Take Ownership’ of the file C:\Windows\system32\MP3DMOD.dll and append .bak to the file name.  I had to rename this file back before using MCDU.  Apparently MCDU is actually a nice GUI front end for renaming this file and setting some registry values that correspond to the defaults for the audio and video decoders.

So check out MCDU if you are having decoder problems, it might just fix your problems!

My last remaining issue is with audio, specifically with mute.  It works with my remote as expected initially, but after some unknown event, the mute button refuses to have any effect.  If you’ve managed to fix this, please let me know how!

mount error(12): Cannot allocate memory
Refer to the mount.cifs(8) manual page (e.g.man mount.cifs)

After checking the Event Viewer System log, I found the following error:

Source: srv
Event ID: 2017
Level: Error
The server was unable to allocate from the system nonpaged pool because the server reached the configured limit for nonpaged pool allocations.

Some research led me to find this Google Groups discussion about the problem and this Microsoft Technet article discussing the solution (look at the bottom of the page).  Apparently you need to tell Windows that you want to use the machine as a file server and that it should allocate resources accordingly.  Set the following registry key to ’1′:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\LargeSystemCache

and set the following registry key to ’3′:

HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\Size

After making these changes and restarting, I haven’t seen this issue arise again.  Fixed!

Update (2011/9/16): I had no idea this fix would end up being so popular when I wrote it up.  It is easily the most visited page on this site.  The original Technet article seems to be gone now, but a commenter has pointed me to a text file that contains the same content.  Here is the link: http://www.decuslib.com/decus/vmslt99a/nt/tips.txt

More detailed steps are as follows:

1. Install AC3Filter
2. Install the ‘Take Ownership’ registry hack
3. Take ownership of ‘C:\Windows\system32\MP3DMOD.dll’ (right click -> Take Ownership)
4. Rename ‘C:\Windows\system32\MP3DMOD.dll’ to ‘C:\Windows\system32\MP3DMOD.dll.bak’
5. Get the CLSID of AC3Filter using Radlight’s Filter Manager.
6. Set the registry key ‘HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\ CurrentVersion\MediaCenter\Decoder\PreferredMPEG2AudioDecoderCLSID’ to the CLSID from the previous step.

A restart may be required here.  After doing this, all audio for media center should be piped through AC3Filter.  Now one can adjust the settings in AC3Filter to adjust gain, surround settings, equalizer settings, etc.

I’m now able to control all my audio using the system volume rather than my stereo’s volume.