Problem

A customer using a Mac wishes to set up an automatic back up of their machine using the built in Time Machine backup software.

Resolution

Time machine is a useful automatic tool or backing up user files from a Mac.  Please makes sure of the following to start a Time Machine backup:

1. You have an external drive that is formatted and erased (without losing data).
   
2. Time Machine requires the backup drive must be solely used for back up of Time Machine unless the physical drive is exceptionally large in which case one should create a new volume to host the backup files separately from other user data.  Please see create an APFS volume for Time Machine backup.  Please note that creating any such volume will reduce the total available capacity on the drive. 
   

Step 1 – Set up Time Machine

1. Click Apple menu (top left corner of screen) then choose System Settings.
   
2. Click General in the sidebar, and click Time Machine on the right-hand side.
   
3. Click Add Backup Disk or click the Add button (+).
   
4. Select your connected storage device and click Set Up Disk.
   
5. During the setup process:
   
6. Your Mac may ask if you want to erase the storage device so that it can be used for Time Machine. Either erase it or select a different backup disk or volume.
   
7. After Time Machine set up the back up will begin immediately start using the storage device to make backups.

Step 2 – Start a Time machine backup

Look for the time machine icon in the menu bar at the top and click it, then click the item Back Up Now, the back up will then be started.  If you see Skip This Backup in the menu shown below a backup is already in progress and you ay click it to interrupt the backup.

The back up may take some time to complete (especially first initial back up) please leave the external drive connected to the Mac so it can continue to back up files automatically.   If the drive is disconnected and then connected Time Machine will start back up on the next scheduled time or you can click Back Up Now within the Time Machine menu.

Reduce back up size

Time Machine creates a back up every 24 hours over a rolling 30 day period where the oldest backup is overwritten.  Using the default settings this may take up excessive amounts of space if there is a lot of data to backup.  One can reduce the impact by adjusting some of the settings to have it back up less frequently than default.

1. Click the Time Machine icon then choose Open Time Machine Settings.
   
2. In the settings panel click Options, then click Frequency. 
   
3. From here you can reduce the frequency of the back up to conserve disk space.