This post is mainly to remind me of the procedure to follow, in that a little searching on the web will find the answers. However, when I am in front of a client’s mac I would prefer to have the answers in one place.
1) Enable Time Machine’s latent ability to back-up to other kinds of disk. Copy this into an open Terminal window:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
and press return.
2) Mount the network disk* that you want to back-up onto. Make sure you can see an open Finder window with its contents.
3) In Time Machine preferences choose this disk as the target for the back-up.
4) As Time Machine tries and fails to create a back-up on this target disk, watch the open Finder window; a disk image file will appear there called something like: “MacName_0016cb8c8882.sparsbundle“. As it does so, select its name and copy it. Paste the name somewhere for later. (The “MacName” will be the name of the Mac, the alphanumeric will be the hardware address of the ethernet card used for networking).
5) Time Machine will eventually complain that the back-up failed. Ah well.
6) Find where you pasted the name of the sparsebundle file Time Machine tried to create. Below it paste this code:
DISK_IMAGE_NAME=”Mac_number.sparsebundle” DISK_SIZE=110000 hdiutil create -library SPUD -megabytes $DISK_SIZE -fs HFS+J -type SPARSEBUNDLE -volname “$DISK_IMAGE_NAME” “$DISK_IMAGE_NAME”
7) Replace Mac_number.sparsebundle with the actual sparsebundle name saved earlier. Retain the ” ” double quotes! Determine whether a disk size of 110000 MB is enough for a back-up disk and adjust the figure accordingly. Copy and paste the revised code into a new Terminal window and press return. This will create a disk image file with the same name as the one that Time Machine failed to create. It will at first be small but grows in size as files are backed-up. Copy this new file to the networked disk.
Time Machine will now be able to back-up. The first back-up will be huge and take days, so in the Time Machine preferences, select lots of folders to omit from the back-up in the Time Machine. Then the first sync will be small. The missed folders can be activated later.
*Network disk: If the disk is being shared from another Mac you may have to fiddle with its permissions until Time Machine will see it. For me, using a firewire disk shared from a Mac running Panther, giving everyone read-write access and un-checking ignore ownership on this volume did the trick:
Credit:
http://adamcohenrose.blogspot.com/2008/02/time-machine-wireless-backup-without.html
http://forums.macrumors.com/showthread.php?t=427488
http://www.macosxhints.com/article.php?story=20080420211034137
