![]() ![]() And the entire image is treated as a single huge file, so it’s not efficient to update a copy of it after you’ve changed something. When you create a disk image, you must specify the size of the virtual disk drive, and this space is typically consumed immediately regardless of how much data you actually write to it. So a 1 TB disk image will take up 1 TB of actual capacity on whatever drive you write it to. Sure, you could encrypt your whole drive but this isn’t always desirable for removable media (portable hard disk drives and thumb drives) since you often want to have some “wide open” space, too. ![]() Create a disk image with encryption and you can move it around from drive to drive or machine to machine without having to worry that someone else will get their hands on the content. My favorite use of disk images is as a secure, encrypted drive for important data. It could be a virtual hard drive for a virtual machine, a copy of a DVD or Blu-Ray disc, or an archive for an application that wants to use an entire disk. ![]() A disk image is a file on a disk that acts like a separate disk. Buy a 4 TB hard disk drive and you can format it and store (about) 4 TB of stuff on it.ĭisk images are a little less familiar to average folks, but they work pretty much the same way. We’re all used to dealing with hard disk drives and thumb drives: They offer raw “block” storage that is formatted with a file system and used by the operating system, applications, and us users. I suppose I should start with a bit of background info on why I love sparse bundles so much. So I thought I’d write up a bit on what they are and how they can be used. This is again using a sparseimage - but this time the time machine gui shows all backups - no option clicking or anything )īoth my machines are now backing up to the NAS and from the ReadyNAS forums you can see that system restore also works (although I've not yet tested it personally).I’m a big fan of “sparse bundle” disk images in Mac OS X. They allow me to create encrypted repositories for valuable data that can efficiently be rsync-ed between disks and don’t waste a lot of space. However - a new firmware for my NAS (ReadyNAS NV ) now includes the ability to use it as if it were time capsule - you enable Time Machine support and it then just appears in the list of available drives. I have also not tried restore of OSX from a Time Machine backup.Īt this point I repartitioned the disk to give to real partitions. I wonder if the backup process detecting the sparseimage says "find an image with servername and mac address of en0" but the restore process says "find an image with servername and the mac address of the network connection in use" or something similar. I'm not sure why this is failing - it is the same technology that is used to support Time Machine on a Time Capsule - just that its local and not over the network. However - I do prefer the -nospotlight setting - I don't really want my time machine files turning up in spotlight searches. And in this case I seem to need the sparseimage mounted first. ![]() Volumes/Drivename/HOSTNAME_MAC.sparsebundleĪgain - although backup works - restore shows only one backup - you have to option click the time machine icon and choose "Browse other Time Machine disks" - and then select the sparseimage. fs "Case-sensitive Journaled HFS " -volname "Backup of HOSTNAME" \ Then it will run: hdiutil create -nospotlight -imagekey sparse-band-size=131072 -size 500g \ This drive is also included by spotlight - you have to add it to the Private list for spotlight config to exclude it.Īgain this will handle finding HOSTNAME and MAC. This grabs both HOSTNAME and MAC for you and then runs: hdiutil create -size 500g -fs HFS J -volname "TM-backup-of-HOSTNAME" /Volumes/Drivename/HOSTNAME_MAC.sparsebundleīut - although backup works - restore shows only one backup - you have to option click the time machine icon and choose "Browse other Time Machine disks" - and then select the sparseimage backup. MAC is the mac address of the network adapter: ifconfig en0 | grep ether | sed -e "s/.*ether //" | sed -e "s/://g" To do so - you can use the same technology as time capsule does - sparseimages. Having a very large external disk I wanted to limit Time Machine to use only part of it. ![]()
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