How to control the size of time Machine backup files

By default, time Machine continues to back up until the backup disk is full when the Machine is used as a backup.

This is fine when your backup disk is dedicated to a time Machine backup and not used for other purposes.

But what if you don't want to use the entire backup disk for a time Machine backup, and you want to make a portion of the backup disk available for him, and you can't partition the backup disk (for example, when the capsule can't repartition)?

First look at how time Machine backups in the backup disk.

Time Machine creates a "sparse bundle of disk images" called Computername_xxxxxxxxxxxx.sparsebundle on the backup disk, which is used to store the backup data, time Machine will continue to add data to it and increase the size of the image until the backup hard disk fills up.

The solution is to create a disk image of a specified size before using time Machine, and then turn on time Machine so that the time Machine's backup file size will be limited to the size of the disk image of the specified size, without filling the entire backup disk.

For example, you can set up a 300Gb disk image on a 1TB hard disk, and then specify this hard disk as the backup disk for time Machine so that time Machine will only be backed up with 300Gb, and the remaining 700Gb can be used for him.

Specific mode of operation:

The computername_xxxxxxxxxxxx.sparsebundle image mentioned above has a file name consisting of two parts.

The ComputerName is the name of your computer that you can see in the system overview, displayed in the upper-left corner.

XXXXXXXXXXXX is your computer's Ethernet ID, which you can choose from "Network"-> "Ethernet"-> "Advanced ..." in "System Preferences"-> "Ethernet" is a 12-bit string, including numbers and letters, but excluding colons. Note that it must be an Ethernet ID, even if your computer is not connected to Ethernet, or is connected to WiFi.

The computer name and the Ethernet ID are underlined.

Once you know this, you can create an image on the backup disk.

First deactivate time Machine.

Then, when you open Disk utility, select New image on the toolbar, select the location of the new image (that is, your backup hard disk), and then follow the diagram to set it.

The name of the image according to the previous text of input, size according to your personal taste.

After the image is established, open time Machine and point the backup disk to the hard disk on which the image resides, and you are done.

If you are unsure about the name of the image (or if you can't find your computer's name or Ethernet ID), you can also run time Machine first, make a backup (to save time, make it back up a very small amount of data), and let it build an image of itself. Then you copy the name of the image, then stop time Machine, delete the image it created, and then recreate the image by pasting the image name you just copied.