Time Machine Tip

If, like me, you are frustrated by the fact that you have a 'book or just don't want to be tied to an external drive to use Time Machine, but have another Mac on your network or an NAS disk you could use here's a great tip.

Open Terminal then copy and paste the following:

defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

Now hit return, close Terminal and mount your shared volume.

Opening Time Machine now allows you to select the shared volume as a backup location.

This is clearly an unsupported feature (probably because Apple wants you to buy Time Capsule instead!). It seems to behave exactly as OS X Server does in terms of hosting backups when you do it. Unlike the normal Time Machine backup on a local volume, this will create a sparse disk image on the host machine, which mounts all by itself whenever Time Machine starts backing up - you do not need to have the disk you selected as the backup mounted for Time Machine to do its thing. Obviously, if you are not on your home network the backups will fail, but they will start again as soon as you are connected to it.

I've only tested this on AFP shares. I can't be sure it will work with Windows shares. If it does the share will need to be an NTFS volume, not FAT32.

Des... that sounds inordinately useful, thanks

Just one question, I'll take my case of an iMac with en external drive used for TM, and wanting to back up a Macbook: can I use the same drive to backup both into one volume, or will I need to partition the current TM drive to give each its own volume? Or, as a last resort, get another drive for the Macbook?

I hope that makes sense

It makes perfect sense. And, yes, you can use the same shared volume/folder for as many machines as the the share has space for. Each connected machine will create its own sparse image. To make any drive or folder on it available all you need to do is enable file sharing and make the drive or folder a share in sharing preferences. Of course, the user will need to be made a user on the host machine for them to have access to the share.

I should add here that this is of limited use for backing up the system files since you can't access the backup from an OS X boot CD to restore the entire system (to my knowledge anyway). I only backup my home folder and other data, though.

Excellent, thanks Des . I'm not too bothered about system backups, that's what the install CD and plenty of download allowance is for

When I first started with TM I got a 500GB external drive and thought it would be more than ample. Since then I've got into iTunes and Apple TV with the library on an external 1TB drive, and things are getting cramped... I'm beginning to see an excuse for getting a 2TB drive

The amount of data we keep just keeps rising. I just got a 1.5TB drive for this reason...... and I remember the day I got a Mac with what seemed at the time an absolutely colossal 20MB hard drive that I thought I'd never manage to fill. That became a very expensive 40MB one...... 80MB one....... 120MB one..... 500MB one....... 1 GB..... 2GB..... 4GB.......... 8GB.............. 12GB............... 20GB.................. 40GB........... 80GB.................100GB................ 200GB.................................... 500GB.......................................................... 1TB..... Now 1.5TB is what I need to back it all up and I don't back up my Windows Media Center TV recordings at all.

Edited by Desmond (Thu 12-Feb-09 22:51:54)

a very expensive 40MB one

I remember when I added a 200MB drive to my first PC... iirc HDD capacity then was about £1.25/MB, and everybody marvelled how cheap it was becoming.

And I shudder to think what a now routine 2GB of RAM would have cost

When I worked for RM I had to sign out 64MB of PC RAM (2 SIMMS) from stores to fit in the latest server (Pentium I 90MHz) - the stores price (i.e. internal cost to the company) was about £700! That was probably quite a long time ago