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I found my .MobileBackups folder quite large, it weights 160 Gi. Shouldn't the .MobileBsckups folder be wiped after the TM 'backup session'?

Since I have backup done on my external drive how can I get back my 160Gi of hdd space? Can I simply remove this folder or maybe set some limit of mobile backups?

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New in OSX 10.10.1 (for me at least ...). When, in Time Machine preferences, you turn Time Machine OFF and later turn it ON again, local backups come back like a recurring nightmare. Must disable local again. – YvesLeBorg Nov 22 '14 at 13:03
up vote 45 down vote accepted

To disable local backups issue this command in terminal:

sudo tmutil disablelocal

This almost never is necessary as the system will automatically prune and disable local backups as your drive fills. You can search for backupd using the console app to see if and when the storage cleanup happens due to low space.

There is a lot of confusion as to the purpose of local snapshots. It's not to take snapshots that then get dumped to your actual Time Machine drive when you run a backup, it's a separate set of snapshots that let you restore files you've accidentally changed or deleted, when you're away from your Time Machine drive. It's not a true backup -- it won't help you if your laptop's drive fails -- but it will help out if you're on the go and you accidentally lose something while on the go. As such, they don't get cleared out after TM backups.

On my computer (a Macbook Air with flash memory), it deletes old mobile snapshots after a week. The behavior may be different on devices with hard drives, as they don't experience longevity issues with full disks. According to Apple's documentation, they aren't deleted after a week. Note that the available space shown in Finder does not take into account the local snapshots, because they will automatically be deleted if you need the space, and it will automatically keep at least 20% of your disk space free -- so you generally shouldn't worry about space taken up by local snapshots. However, if you don't want them around, you can disable them with the command sudo tmutil disablelocal. This will free up the space taken by your local snapshots, and if you reenable it with sudo tmutil enablelocal, it'll start again with an empty set of local snapshots. So, a quick way of clearing out what's on there is to disable and re-enable local snapshots.

You can see how many old backups are being stored by activating Time Machine. White tick marks indicate local snapshots, and purple ones indicate real backups.

There's more information from apple and here.

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After temporarily disabling the feature (in order to clear the space one time), do we have to reboot? wait some time? It's not clearing up for me – huyz Aug 20 '14 at 21:51
Answering my own question, it can take a day or so apparently. Pondini, Time Machine guru, says: "Normally if you either run sudo tmutil disablelocal or turn Time Machine OFF, they will be deleted. If your disk is over 90% full, it's done at a high priority, otherwise at a lower one, so it can take a while. However, on rare occasions, there's something corrupted preventing them from being deleted. You may have to Restart, look in the trash for recovered items and force-delete them." – huyz Aug 20 '14 at 21:56

This is a virtual folder. And displayed size is not actual, there is only changed files copied, but displayed total size of all data. Removing MobileBackups will not make 160 gb more free space.

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It will make more free space in terms of what tools like du report. I just ran sudo tmutil disable local ; sudo tmutil enable local (thanks, @cablesm) and as a result, du reports another 38 GB free, which I need at the moment. – Matthew Elvey Aug 9 '14 at 20:58
Under El Capitan, the Finder definitely does report space used by .Mobilebackups. Doing a sudo rm -fr .MobileBackups instantly frees up many gigabytes of space. – odysseus Nov 9 '15 at 12:32

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