I have limited storage on a NAS to which Time Machine backs up documents. I’ve excluded system file directories and a few more to save space. I also have a large portable drive. A few times a year I back up pretty much everything to that.

Right now, I’m doing that by removing one drive before adding the other. Then I change the list of excluded folders, wait till the backup is done and repeat.

Is there a quicker, more reliable way to do this?

  • There's a script here (from back before TM supported multiple targets natively) that might be adaptable. Basically, set up for one backup target, copy /Library/Preferences/com.apple.TimeMachine.plist, change it for the other target, copy that version, then swap them back & forth depending on which target you want to back up to today. – Gordon Davisson Jun 6 '19 at 0:44
  • This was the kind of thing I was looking for, but I'm hesitant to use it as even with sudo macOS doesn't let me open the file for manual edits: 'EPERM: operation not permitted'. – kslstn Jun 10 '19 at 13:44

"A few times a year I back up pretty much everything to that."

I suggest you use a cloning software package for making your once in awhile copies.

I use Time Machine to get a historic copies of my files and a cloning software package to get a bootable clone of my Startup Disk.

Carbon Copy Cloner will copy your Startup Disk to an external FireWire drive. You can boot from the external drive to verify that you have a good clone. When you upgrade your existing Startup Disk, you can at any time boot from your external drive and go back to your existing system.

Slightly modified excerpts from SuperDuper's webpage...

SuperDuper is the wildly acclaimed program that makes recovery painless, because it makes creating a fully bootable backup painless. It's incredibly clear, friendly interface is understandable, easy to use, and SuperDuper's built-in scheduler makes it trivial to back up automatically. And it runs beautifully on both Intel and PowerPC Macs!

Give SuperDuper a workout on your own system. Clone to your heart's content, for free. See what else is possible. When you're convinced that SuperDuper is a terrific solution — and a great value at $27.95 — you can register right from the application and start using its advanced features immediately!

Disk Utility Apple has included an option in Disk Utility – ‘Restore’. This option in Disk Utility allows you to copy the entire data of your hard disk to another hard drive or any external media.

dd command

-- the dd command is not for amateurs. -- you have been warned. --

You can use the dd command to backup a drive or partition. You need to be familiar with /Applications/Utilities/Terminal. I added this section for completeness.

# save
dd if=/dev/disk0s10 bs=4096m | gzip | dd of=~/disk0-s10 bs=4096m
# restore
dd if=~/disk0-s10 bs=4096m | gunzip | dd of=/dev/disk0s10 bs=4096m

This is riskie if you have never done it before. It may be hard to figure out the correct drive name.

How do use dd:
get a second disk the same size or larger.

What the unix name of the disk will be depends on how you attach the disk. 

without the old drive attached to
diskutil list

attach the new drive before booting.
repeat the above so you can figure out the name.

Now, that you name the names, you can copy the old disk, /dev/disk0,  to the new disk, /dev/disk1.  

sudo dd if=/dev/disk0 bs=4096m |  sudo dd of=/dev/disk1 bs=4096m

# this command should do a block by block copy
# this way you will get the whole disk.
# if= is input
# of= is output

mac $ diskutil list
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         999.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macintosh HD           *999.0 GB   disk1
                                 Logical Volume on disk0s2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *4.0 TB     disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:                  Apple_HFS Backup - Mac Mini       999.3 GB   disk2s2
   3:                 Apple_Boot Recovery HD             784.2 MB   disk2s3
   4:                  Apple_HFS Backup - Time Machine   2.0 TB     disk2s4
   5:                  Apple_HFS Boot - for Fun          49.5 GB    disk2s5
   6:                 Apple_Boot Recovery HD             650.0 MB   disk2s6
   7:                  Apple_HFS 1T Backup               985.1 GB   disk2s7
mac $ 
mac $ df
Filesystem      Size   Used  Avail Capacity   iused    ifree %iused  Mounted on
/dev/disk1     930Gi  864Gi   66Gi    93% 226596185 17296037   93%   /
devfs          193Ki  193Ki    0Bi   100%       669        0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%         0        0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%         0        0  100%   /home
/dev/disk2s2   931Gi  765Gi  166Gi    83% 200428475 43553456   82%   /Volumes/Backup - Mac Mini
/dev/disk2s4   1.8Ti  1.6Ti  147Gi    92% 441119165 38598628   92%   /Volumes/Backup - Time Machine
/dev/disk2s5    46Gi   29Gi   17Gi    63%   7590207  4490899   63%   /Volumes/Boot - for Fun
/dev/disk2s7   917Gi  771Gi  147Gi    84% 202019436 38487474   84%   /Volumes/1T Backup
mac $ 


  • Thanks for suggesting a different approach. Are there other benefits to that? I’m hesitant to add another tool to depend on. – kslstn Jun 5 '19 at 12:05
  • There are two benefits: (1) you don't have to mess with your existing settings. (2) you have a bootable backup. So, you can verify that your backup works and if you have a problem, you can instantly be back and running. I've been using CCC for ten years. If you need something free, you can use disk utility or dd command. dd, being a command, has limitted safety checks – historystamp Jun 5 '19 at 21:43
  • Warning: dd does not properly handle expanding or shrinking volumes -- you should only use it if the source and target are exactly the same size. asr restore --erase (the command-line version of Disk Utility Restore) is much better at this. – Gordon Davisson Jun 6 '19 at 1:01
  • BTW, I do approve of using a different method for the other backup. Diverse backups give more redundancy than similar backups. – Gordon Davisson Jun 6 '19 at 1:03
  • I did say "This is riskie if you have never done it before." The drive needs to be the same size or bigger. The same goes for the partition. For a bigger drive or partition you can run disk utility verify and correct to fix up the drive or partition. I did it a long time ago with a mac os extended partition. If you do nothing, you will not be able to use the extra space. You will be able to use what space you have allocated. All of this is based on macOS extended partition formatting. I'll add a bigger warning. – historystamp Jun 6 '19 at 4:44

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