Hello 👋 I'm Dan.

I write PHP, Go, and JavaScript. I also care about web performance.

No mountable file systems

Unable to attach "faulty.sparsebundle" (No mountable file systems)

Unable to attach "faulty.sparsebundle" (No mountable file systems)

Recently I had an issue where a friends Legacy FileVault sparsebundle became corrupt when they upgraded to OS X Mavericks. Whenever they logged in and tried to mount their home-foldered sparsebundle, the error “No mountable file systems” would appear. Even cloning the sparsebundle and trying on another computer resulted in the same problem. My initial thoughts are “Shittt… all the data is gone”, but I know that just because I get a generic error message, doesn’t mean I can’t fiddle around and get it working again. Here are the steps I followed to mount the “corrupt” sparsebundle and recover all the data in the process.

First up, as you would have tried, mounting the sparsebundle through DiskImageMounter.app doesn’t work. Never fear, the command line is here! Using the hdiutil command in Terminal, we can attach the sparsebundle to the filesystem without actually mounting it. We’ll also add a few flags to tell hdiutil that we don’t want to verify or check the checksums of the image (which are probably causing it to fail mounting in the first place). Here’s my final command to attach the sparsebundle to Mac OS X:

hdiutil attach -nomount -noverify -ignorebadchecksums /path/to/faulty.sparsebundle

After a few seconds you’ll get prompted to enter the password to unlock the sparsebundle (if it’s encrypted) and then it’ll be attached to OS X. You’ll get a list of the BSD /dev node along with with the human-readable GUID of the partition (do man hdiutil to find out what I mean). Here’s the output of when I mount my faulty.sparsebundle:

/dev/disk3     Apple_partition_scheme
/dev/disk3s1   Apple_partition_map
/dev/disk3s2   Apple_HFS
Attaching faulty.sparsebundle to OS X via Terminal.

Attaching faulty.sparsebundle to OS X via Terminal.

Okay, now that the sparsebundle has been attached to OS X, it’s time to open one of my favourite programs of all time: DiskWarrior. fsck_hfs just doesn’t cut it, but DiskWarrior will often always work its beautiful magic and get drives mounting for me again. Once you’ve got DiskWarrior open, it’s time to repair the disk! The attached volume is very likely called “Unknown Disk”, just select the one that’s most likely to be your attached sparsebundle.

Getting Ready to Repair "Unknown Disk" in DiskWarrior.

Getting Ready to Repair "Unknown Disk" in DiskWarrior.

Now, in my friends case, doing a “Scavenge” rebuild and repair in DiskWarrior would recover only a few files, but doing a normal rebuild would recover all the files. I would normally try doing a normal rebuild first and checking the preview, it’s really trial and error. Go ahead and click Rebuild then wait until DiskWarrior has finished and shows you the Rebuild Report. Instead of clicking Replace, we’ll go ahead and click Preview.

DiskWarrior's Report on Repairing "Unknown Disk".

DiskWarrior's Report on Repairing "Unknown Disk".

Jump back to the Finder and open up the Previewed ‘faulty’ volume, or list the contents of the volume in Terminal:

ls -la /Volumes/faulty/
Showing the Contents of faulty Via Terminal.

Showing the Contents of faulty Via Terminal.

You should now see all of your stuff! I would now ditto, rsync, cp, or Carbon Copy Clone all of your files out of that sparsebundle ASAP (and avoid using Legacy FileVault ever again). Hopefully this has helped you (or someone you know) recover your precious data from a corrupted sparsebundle (or Legacy FileVault disk image).

Caching Server Nagios Script Updated With Port Checking

I’ve just updated the Nagios script for OS X Server’s Caching Server with support for ensuring Caching Server is running on a specific port.

In a normal setup of Caching Server, it has the ability to change ports during reboots, and if you have a restrictive firewall, you’ll have to specify a port for Caching Server via the command line. You can specify the port via the serveradmin command (make sure you stop the service first):

sudo serveradmin settings caching:Port = xxx

The xxx is the port you want to use for Caching Server. Normally, Caching Server will use 69010, but depending on your environment, that port may be taken by another service and so Caching Server will pick another port. Using that command above will get Caching Server to attempt to map to the specified port, but if it can’t it will fall back to finding another available port.

The script checks the port as defined in serveradmin settings caching:Port and cross-references it with serveradmin fullstatus caching:Port. If they are the same, we’ll continue through the script, but if it doesn’t I’ll throw a warning. Naturally, if serveradmin settings caching:Port returns 0, I skip any further port checks because a 0 port means randomly assign a port.

Check out the code on GitHub

Caching Server 2 and iOS 7 Confusion

So it appears there is some confusion in the Apple community about whether Caching Server 2 actually caches iOS 7 app downloads. Numerous posts have been popping up saying “No, you’re wrong, it doesn’t cache iOS 7 downloads!”. I’m here to say, no, you’re wrong. It does. After some extensive testing, I will now elaborate.

First off, I’m going to install a program called Charles that acts as a proxy server. Install Charles, set it up then have your iOS device route requests through Charles so we can see exactly what’s happening. Now, before I continue, I must let you know that the app I am about to download was one that I had previously downloaded a week ago, but then deleted (my partner and I were using it for her university project) so it has already been cached on my Mavericks Caching Server. This article isn’t about the initial caching process, more about proof that it does in fact serve cached iOS App Store downloads. I have a standard OS X Mavericks Server running on a 2010 Mac mini with healthy DNS and 1 subnet, and my iPhone is running iOS 7.0.3.

The App Download In Charles.

The App Download In Charles.

Right, so I load up the Purchases tab on my iPhone and tap on the app to download it. Now this app in question is Metronome, a small app that is 18.7 MB in size. Make sure you remember the size because it’s important. Just before I downloaded the app I opened up Charles and started a recording session. The app downloads pretty quickly and I check out what Charles has captured.

The Caching Server's Proxy Tree.

The Caching Server's Proxy Tree.

So far, it looks good. As you can sort of see by the image, my caching server at on port 61090 responded to an App Store download request. How is that possible when Caching Server 2 doesn’t support iOS 7 app downloads? Oh wait, it does. My bad. Let’s investigate further:

My Caching Server's Response Size - Go Figure!

My Caching Server's Response Size - Go Figure!

Basically, that image shows that the response from my caching server was 18.72 MB in size. Wow! Didn’t I say that the app was 18.7 MB in size? Yep, I did. But wait, that’s not the only piece of evidence I’m going to use to prove that I’m right. Next, I’m going straight to the source. Caching Server 2 stores all of the cached metadata in a database called AssetInfo.db. I’m going to copy that to the Desktop using Terminal (the folder it resides in isn’t accessible by standard Finder means).

Okay, I’ve copied the AssetInfo.db from /Library/Server/Caching/Data/ and opened it up in Base, which is a program to work with SQLite 3 databases. After opening AssetInfo.db I loaded up the ZASSET table and export all rows as a CSV. I then opened up the CSV in Excel (Oh Numbers? We all know Numbers has excellent CSV support…). Next, copying the UUID from the URI in Charles, I pasted that into a search field in Excel, and to my surprise, a row was returned! (I lie, it wasn’t a surprise. I expected it to return a result). You could also do this in Terminal, like this:

sqlite3 /Library/Server/Caching/Data/AssetInfo.db 'SELECT * FROM ZASSET WHERE ZURI LIKE "%8bbfacac-c1ed-b397-e6cd-9110eb87001b%"'

Which gets me this beautiful result:

177|1|5|0|19624091||404215540.806059|daa32fb0fc47da467fd693e12262c318|6FCE511E-C2B2-4449-99E2-0B5EC9F919B4|Fri, 07 Dec 2012 03:15:24 GMT|/au/r1000/070/Purple/v4/8b/bf/ac/8bbfacac-c1ed-b397-e6cd-9110eb87001b/mzps1125351636230933757.D2.dpkg.ipa|

Now, one of those fields is the ZURI (aka the URI that Caching Server uses). When examining the URI in Charles, you can see the URI is the same:

Of course you exclude the IP address as it’s the caching server address on my LAN. The URI matches the AssetInfo.db’s ZURI field and guess what? The ZLASTMODIFIEDSTRING is the exact same date that the last update for Metronome was published (7th December 2012). I also found that the ZTOTALBYTES field, when converted to MB in Base-2, equals… 18.7 MB (which in itself is unusual, the rest of caching server calculates bytes in Base-10). Also, doing a Get Info on the binary file reveals the exact same byte count as ZTOTALBYTES.

Further to that, when I navigate to the actual binary (stored at /Library/Server/Caching/Data/<GUID>/0 by default) and enter md5 /path/to/file I get the same hash that is stored in ZCHECKSUM. For example, the hash for Metronome in the ZCHECKSUM row is daa32fb0fc47da467fd693e12262c318. Then, in Terminal I entered:

md5 /Library/Server/Caching/Data/6FCE511E-C2B2-4449-99E2-0B5EC9F919B4/0

Now, my result was daa32fb0fc47da467fd693e12262c318. Let’s compare them:

daa32fb0fc47da467fd693e12262c318 # ZCHECKSUM
daa32fb0fc47da467fd693e12262c318 # md5 Result in Terminal

Yep, they’re identical. Fact-based proof that OS X Mavericks Server’s Caching Server provides cached iOS App Store downloads to iOS 7 devices.

Now, this article has come off very douchey, but I felt it was necessary to prove to people that Caching Server 2 in OS X Mavericks Server does cache iOS app downloads.

FreeRADIUS Monitoring Script Updated for Mavericks

I’ve updated the FreeRADIUS monitoring script for Nagios with support for OS X Mavericks Server. Mavericks changed the way the FreeRADIUS server is started, along with the paths of execution and storage.

Like the update to the Caching Server 2 monitoring script, I had to write a check to see if the current OS is running 10.9, and if it is, perform a Mavericks-specific check. Like I mentioned in the other article, doing a version check and comparison isn’t particularly easy in Bash, but thankfully, I only have the compare the major and minor release numbers which is nice given that it’s also a float. Using bc (the arbitrary precision calculator language - I should get that on a shirt!) I can quite easily calculate the difference between 10.8 and 10.9. Anyway, check the code below for how I get the version number.

sw_vers -productVersion | grep -E -o "[0-9]+\.[0-9]"

Next, the comparison is performed to see whether the current OS is less than 10.9. If the current OS is less than 10.9, 1 is returned. If it’s the same (or greater), the result is 0. This code is below:

echo $osVersion '< 10.9' | bc -l

Note that the above example requires the variable $osVersion. If you were hard coding the values, you could do something like below:

echo '10.8 < 10.9' | bc -l

The major difference in my script for OS X Mavericks is now there’s actually a process running called radiusd! Using ps and grep I now check to see if the FreeRADIUS server is running by doing this:

ps -ef | grep radiusd

Which, if the FreeRADIUS (or radiusd) is running, will return a non-empty string. If you run that and get an empty string (or nothing) back then your FreeRADIUS server isn’t running. Shit. I recommend doing radiusd -X to start your RADIUS server in debug mode. That or you forgot to get RADIUS added to launchd by entering radiusconfig -start. Anyway, that’s enough chit-chat, just get the damn code from the link below:

Check out the code on GitHub!