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Deleting/Erasing a partition

Avatar Drew McFarlane
13” MacBookAir Mid 2011 – OS Sierra 10.12.6 – 2 Partitions.

Whilst in conversation at the Dorchester meeting on Tuesday I happened to mention that I was about to update to Hi Sierra.

I was advised to delete one of the partitions before updating.

Yesterday morning, after backing up my computer I attempted to delete the aforementioned petition. Unfortunately I came unstuck and had difficulty in completing the task.

I have reached the Disk Utility window with the SSD showing the 2 partitions on the left. On the right I have a thick blue/red line with blue and red dots underneath again showing the partitions.

When I click the upper icon on the left, I have the option from the uppermost icons under Disk Utility to click First Aid or Partition.

After clicking Partition another window opens with a large circle split in half showing the 2 Partitions.

Please may I have instructions on how to complete the task. I have tried everything but cannot merge the two into one.

Re: Deleting/Erasing a partition

Avatar Mick Burrell
I was not party to the conversation but it may be that the suggestion was not to merge the two partitions but to erase one (assuming you've finished with the contents or have sufficient backups of it elsewhere) and do a clean install there before migrating your data from the other. Just a guess - I think this is Euan's preferred method.

Re: Deleting/Erasing a partition

Avatar Drew McFarlane
Thank you Mick, I don't want any partitions.

Re: Deleting/Erasing a partition

Avatar Euan Williams
No one 'has to' have more than one partition unless they find two or more to be useful.

If you run your internal SSD with more than one partition, and you upgrade a previous macOS installation (say, Sierra) to High Sierra, the partition containing the earlier macOS will automatically be reformatted from macOS extended (journaled) aka HFS+ to the new efficient Apple File System aka APFS. Any second or third partition would remain HFS+.

This may work well, but, not least because one of APFS's features is that partitions can resize automatically, it seems sensible to ensure that the complete drive volume with all partitions are APFS formatted unless there is good reason not to do this.

My suggestion is to clone or otherwise backup all data on each partition, then erase the "Volume" as a whole -- not just the individual partitions. Clone back your macOS Sierra (or earlier), and then upgrade the macOS along with the whole volume format to High Sierra and APFS.

Only once this has been done should partitions be added (which are then automatically APFS). Individual partitions can be reverted to HFS+, but this is done within the general APFS scheme and should not be necessary.

Re: Deleting/Erasing a partition

Avatar Drew McFarlane
As stated, I have already backed up the system. My intention is to get rid of the second partition so that the hard drive is as it was when I bought the machine.

I have tried without success, i.e. I am still left with two partitions.

I have reached the Disk Utility window with the SSD showing the 2 partitions on the left. On the right I have a thick blue/red line with blue and red dots underneath again showing the partitions.

When I click the upper icon on the left, I have the option from the uppermost icons under Disk Utility to click First Aid or Partition.

After clicking "Partition" another window opens with a large circle split in half showing the 2 Partitions.

Please may I have instructions on how to complete the task. I have tried everything but cannot merge the two into one.

Re: Deleting/Erasing a partition

Avatar Euan Williams
Normally you would select the partition you wish to remove, indicated in the blue circle, and click on the minus sign beneath. As I suggested above, the simplest way to do this if you are having difficulties is to erase the whole drive "Volume".

What follows assumes that you are NOT using APFS with High Sierra on an SSD.

Select the "volume" of the HD (the name will be some sort of tech gobbble-de-gook such as "Seagate/Toshiba/WD XF345543 DH-34HSrev3".

Note: this is not the single (or more) partition(s) traditionally named "Macintosh HD"

If both the Volume AND the Partition aren't visible, look for the "View" icon at the top left of your Disc Utility window, and make sure that "Show All Devices" is chosen.

Once you have selected the Volume, click on "erase" and choose "MacOS Extended (Journaled)", and "GUID partition scheme" (these choices are normally chosen for you automatically).

Erasing will remove ALL data from your drive, so be aware that if you have used Time M/C to backup you will have to reinstall a fresh macOS before transferring your data with Migration Assistant. I prefer to make a Clone which is a complete backup of absolutely everything and can be used to start your mac externally.

If still perplexed I'm happy to do this for you, but there is nothing particularly fearsome to worry about.
 
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