Author Archives: Chris F Carroll

Use a Windows NTFS, or Linux, or other–formatted disk for Apple Time Machine Backups

It is well known that you have to use an Apple formatted disk (HFS+) for Time Machine Backups and you can’t use an NTFS formatted disk, or any of the preferred *nix disk formats with Time Machine.

Except you can.

Gotchas And Caveats

It’s not always a first choice option:

  • If your Windows drive is connected over USB2, it will be much slower than a Mac disk connected over Thunderbolt or FireWire. My first backup of 120GB took about 10 hours, aka all night. But that was still better than no backup whilst waiting for a new drive to arrive in the post.
  • The backup volume will not auto-mount when you plug the drive in. You must manually double-click the <YourMachineName>.sparsebundle in the Finder each time you plug the drive in. After that, Time Machine backups will run as normal.


  • Plug in your foreign-formatted disk and get a read/write driver for it
  • Save the the script from tmMakeImage script in, for instance, your Downloads directory.
  • Open a terminal window.
  • If you saved to Downloads, then something like this should make the script executable and show you command line usage:
    cd ~/Downloads
    chmod a+x tmMakeImage
    mv tmMakeImage /usr/local/bin
  • So if your external drive has a Volume called WinDrive, and your Mac drive is about 250GB then this command should initialise it for Time Machine backups:
    tmMakeImage 500GB /Volumes/WinDrive GO
  • Optionally, follow up with an immediate tmutil startbackup

Opening the Time Machine preferences should now show that you have “Time Machine Backups” selected as your backup drive. Don’t forget to double-click the sparsebundle each time you attach the drive, to mount your Backup Volume and allow Time Machine to do its stuff.


Using Sparsebundles to create HFS+ formatted drive on a ‘foreign’ disk format

Apple created, it seems, sparse images and sparse bundles to solve the problem of saving backups on a network drive. Time Machine uses and recognises them. It will even auto-mount the sparsebundle disk image when you re-attach the drive in order to start running a backup.

Local drives and network drives

Most instructions on the web focus on network drives. Good instructions without any command-line stuff is here: For network drives, the sparsebundle name includes your Mac’s MAC address which it doesn’t need to for a locally-connected drive.

Things Under the Hood of Time Machine Disks

  • You can’t create a sparsebundle directly on a network or ‘foreign’ drive so the typical thing is to create it on your machine first, and then copy it to its final destination.
  • Sparsebundles don’t use up empty space. An sparsebundle declared as 500GB but still empty will only take up a few megabytes of real disk space.
  • A sparsebundle used by Time Machine has a file in the package, which contains the UUID of the physical machine it belongs to. This stops you accidentally using backups on the ‘wrong’ machine. (Time Machine does let you browse and use ‘wrong’ backups though).
  • A Time Machine drive must have “Ignore ownership permissions” Off, whereas by default the Mac mounts external drives with “Ignore ownership permissions” set to On. This setting is not stored on the drive itself; it’s stored on your machine and can be specified each time the drive is mounted (man hdiutil) or specified permanently (man vsdbutil)
  • You can set the Time Machine destination to a sparsebundle on an attached drive by first mounting it then doing tmutil setdestination /Volumes/Volumenameonceitsbeenmounted. You mount the image either by double-clicking it in Finder, or with hdiutil attach /path/to/image.
  • Learn More:
    man tmutil
    man hdiutil
    man vsdbutil
  • You can still use your backup disks for other files alongside your Time Machine backups. Just don’t touch the Backups.backupdb folder! The Finder will protect it to some extent; it doesn’t let you modify things in there, but it will let you delete and add things.
  • The Script

    Most of the things in the tmMakeImage script can be found on the net going back to 2007, but you’ll still find recent answers on the internet saying it can’t be done.

Mac OS X Command Line: Start a process and pick it up later

I can’t believe I’ve only just discovered the gnu screen command. You want to kick off a long running command line process and come back to it later? Like so:

  • Open a Terminal window
  • Type screen
  • Type ls -R /
  • Quit Terminal, and hum to yourself for a few seconds
  • Open a new Terminal window and type screen -R

Now that’s what I call magic.

It survives logouts and is of course an essential for working with remote or cloud machines over ssh; when your network connection fails you can log back in and carry on. man screen will tell you more, although so will

One User, Many Computers

I’ve tried a few solutions for using multiple computers (mostly one MacBook plus one or two Windows machines) simultaneously and I’ve currently landed on as the One for Me.

It’s very good. It’s pretty seamless (last year less so, this years seems perfect) : put 3 machines next to each other, move your mouse across the 3 screens, and control and type into whichever computer has mouse focus. It’s particularly a good solution when some of your machine are laptops and you want to use the laptop screens.

Alternatives I’ve tried:

  • VNC and remote desktop style solutions have worked best for me when I have multiple monitors on a single machine. The irritation is when your local monitor isn’t as big as you want for the remote machine and you end up with a scrolling window. The itch that remote desktop solutions don’t scratch though is when some of your machines are laptops, and then you want to use the laptop screen. Of the various options, TeamViewer and MS Remote Desktop seem the fastest; I haven’t yet seen a fast solution for Mac.
  • When I don’t need a gui, I find ssh or similar is really good. Even a modest monitor easily has room for multiple console windows. A reminder perhaps that guis are not always the bee’s knees.

IIS Express GUI

Looking for a admin GUI so I can start/stop IISExpress websites I quickly found iisexpressgui on codeplex/ which is by Matteo Tontini and iis express manager. They both do pretty much the same thing. They also both only pick up only the first binding for a site, so if you’ve got two — for instance one for http and one for https — then you might need to edit your %Documents%\IISExpress\config\applicationhost.config to choose the one you want to use.