Moving this directory is a real pain, because iTunes doesn’t recognise the move, nor does it have a batch “change the base path” feature (which is sorely needed).

The smartest thing you can do is create a symlink (hint: ln -s in the console) in your iTunes directory that points to your external HDD.  This way, the next time you do a move – all you have to do is modify the symlink!  Even if you move the files back to your main HDD…    so this is what I did (and now I’ll never have to do what I did next again…)

Alas I had to fix some paths from before when I started using this symlink method.  What follows is a summary on how to update the path for 1000s of songs in iTunes (pointing to my new shiny symlink, which in turn points to the external HDD):

NOTE: this is simply what I did.  I don’t recommend doing or not doing anything in this post, use at own risk!

[Apple's Docs on this are here]

1. Close iTunes
2. Browse to your iTunes folder.  Backup the files “iTunes Library” and “iTunes Music Library.xml”.  (restore these if anything blows up).
3. Make another copy of the .xml file somewhere handy, like your desktop
4. Edit this XML file.  Do a find and replace for the directory string you need to replace (hint: to validate the file:// URLs you are using, just copy+paste one into Chrome, if it finds it, you’re all good best to do this to avoid errors).
5. Now open iTunes, and remove all the music and playlists (you can always restore the backup in #2)
6. Then File -> Library -> Import Playlist.  Select the XML file you edited on your desktop.
7. Wait.  This takes ages.

And finally, all my music is back.  By using the symlink trick, I can now move this directory around to my hearts content.  Yey.

Important Note: if you do setup the symlink then make sure when you add new music you drag it from the symlink directory!

Firstly, read Apple’s FAQ

To initiate a backup (these are by default automatically done regularly but sometimes you want to do one anyway), right click on the iPhone in iTunes and click “Back Up”

Essentially, the iPhone backups are stored in a compressed SQLLite format on your HDD (on mac, /Users/yourusername/Library/Application Support/MobileSync/Backup/). So if you want to backup your backups, backup that directory. It’s in your home directory, so Time Machine will normally grab it unless manually excluded.

Now if you’re a developer or just a curious individual, you may want to peek inside those files or extract the data manually. This is quite possible because they are just SQLLite data files. Check out this awesome iPhone backup extraction software for mac. Be sure to send this guy a few bucks as a thank you. You can also do it the old fashioned way with a perl script. I found the perl script however didn’t convert all of my backup.

Actually modifying the data and sticking it back on the iPhone however I don’t believe is possible as it cryptographically signed to protect integrity (which is good for us developers).

Remember as a developer you chose to store files in the users “Documents” or “Cache” directory. Be nice and put anything that doesn’t really matter in the “Cache” directory to save the user’s backup time when syncing with iTunes.

KeepVid – Lets you download iPhone compatiable (and high quality) MP4 files direct from YouTube – just wack the YouTube URL in the box and you’re done. Thanks Pete.

MPEG StreamClip – it’s not often you find a useful and free video tool – but this is one. Drag-drop, convert to MP4 and click “iTunes” for one of the iTunes presets. Pretty straight forward. Mac only.