TimeMachine mobile backup eats up disk space if backup drive unavailable : phaq : http://phaq.phunsites.net

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Export date: Sun Feb 9 5:57:39 2025 / +0000 GMT

Apple introduced a new feature called "mobile backups" with OS X Lion.
The idea behind that: Use a temporary part of the local hard drive to store backups until the backup drive is connected again.

True, this is a good feature for most. But if you can spare some backups, because you - let's say - store your files to a dropbox folder, which is synchronized to a cloud service, then you may not need the mobile backup feature of OS X.
In fact, you may notice running out of disk space, that you could use otherwise.

So to see the difference, let's check out the available free disk space in Termin us the 'df' (disk free) utility:



gianpaolo-del-mattos-macbook-pro:~ Gianpaolo$ df -h

Filesystem                          Size   Used  Avail Capacity  Mounted on

/dev/disk0s2                        79Gi   69Gi  9.1Gi    89%    /

devfs                              129Ki  129Ki    0Bi   100%    /dev

map -hosts                           0Bi    0Bi    0Bi   100%    /net

map auto_home                        0Bi    0Bi    0Bi   100%    /home

localhost:/SkA_FxsNwtVofJZZOc308I   79Gi   79Gi    0Bi   100%    /Volumes/MobileBackups

Gosh, I'm almost out of space, having only 9 Gigs left :-/

So let's get rid of the mobile backups using this command:



sudo tmutil disablelocal

Now check back at the disk space:



gianpaolo-del-mattos-macbook-pro:~ Gianpaolo$ df -h

Filesystem      Size   Used  Avail Capacity  Mounted on

/dev/disk0s2    79Gi   60Gi   18Gi    77%    /

devfs          129Ki  129Ki    0Bi   100%    /dev

map -hosts       0Bi    0Bi    0Bi   100%    /net

map auto_home    0Bi    0Bi    0Bi   100%    /home

You notice, that the '/Volumes/MobileBackups' mount point is gone?
I'm having 18 Gigs free now as well.

So, depending on how long you didn't have your backup drive connected, the amount used may well increase to a multiple of that.

It may not be best choice for most people to have mobile backups disabled. But if you DO know what you're doing, then go for it ;-)