MacOS Mojave Clean Install - Partitions Question Inside

A4orce84

macrumors 6502
Original poster
Apr 17, 2012
288
10
Hello Everyone,

I just purchased a refurb 2018 MacBook Pro and it had High Sierra installed. I prepped a USB Flash drive with MacOS Mojave base install files for a clean installation (format the drive, install from scratch) and noticed upon booting up with the USB drive there is a separate partition called "osx base system partition."

My questions are:
  1. Can I erase this partition and reclaim some space?
  2. Is it safe to even delete this partition, or will I have some issues long-term with updates / upgrades / etc.
Thanks in advance for everyone's time and help, it is GREATLY appreciated.
 

whoisyourdaddy

Suspended
Oct 2, 2018
217
83
Hello Everyone,

I just purchased a refurb 2018 MacBook Pro and it had High Sierra installed. I prepped a USB Flash drive with MacOS Mojave base install files for a clean installation (format the drive, install from scratch) and noticed upon booting up with the USB drive there is a separate partition called "osx base system partition."

My questions are:
  1. Can I erase this partition and reclaim some space?
  2. Is it safe to even delete this partition, or will I have some issues long-term with updates / upgrades / etc.
Thanks in advance for everyone's time and help, it is GREATLY appreciated.
It’s the recovery partition. Even if, you start with a clean disk that’s not partitioned, then it will be created again when formatted for macOS installation.
 

A4orce84

macrumors 6502
Original poster
Apr 17, 2012
288
10
There is no way to forcefully delete it, or even delete it AFTER I install MacOS Mojave?
 

50cc

macrumors newbie
Nov 18, 2018
3
0
Good question, I'm also looking for a way to fully repartition and clean a mac drive
 

marzer

macrumors 65816
Nov 14, 2009
1,329
44
Colorado
Hello Everyone,

I just purchased a refurb 2018 MacBook Pro and it had High Sierra installed. I prepped a USB Flash drive with MacOS Mojave base install files for a clean installation (format the drive, install from scratch) and noticed upon booting up with the USB drive there is a separate partition called "osx base system partition."

My questions are:
  1. Can I erase this partition and reclaim some space?
  2. Is it safe to even delete this partition, or will I have some issues long-term with updates / upgrades / etc.
Thanks in advance for everyone's time and help, it is GREATLY appreciated.
Are you talking about the partitions on the boot media? Can you provide a screen capture or something?

Partitions labeled “osx base system partition” usually exist on the installation boot media and have nothing to do with the internal drive. Of course you would not want to delete it, you’d corrupt the installation media, preventing you from being able to perform an install. But maybe I’m misunderstanding.
 

Fishrrman

macrumors P6
Feb 20, 2009
17,182
5,536
OP:

You don't need to save anything that came on the internal drive, is this correct?

If so, I'd do it this way:
1. Boot from your USB installer. Don't run the OS installer just yet.
2. Open Disk Utility
3. In DU's upper-left-hand corner, there is a popup menu with the choice to "show all devices". That's the choice you want.
4. Now, click on the topmost listing that represents the physical drive
5. Click the Erase button and choose Mac OS extended with journaling enabled. This will be automatically converted to APFS during the Mojave install.
6. Now, close DU and re-open the OS installer
7. Do the Mojave install.

That should do it...
 

macjunk(ie)

macrumors 6502a
Aug 12, 2009
906
504
OP:

You don't need to save anything that came on the internal drive, is this correct?

If so, I'd do it this way:
1. Boot from your USB installer. Don't run the OS installer just yet.
2. Open Disk Utility
3. In DU's upper-left-hand corner, there is a popup menu with the choice to "show all devices". That's the choice you want.
4. Now, click on the topmost listing that represents the physical drive
5. Click the Erase button and choose Mac OS extended with journaling enabled. This will be automatically converted to APFS during the Mojave install.
6. Now, close DU and re-open the OS installer
7. Do the Mojave install.

That should do it...
wasn't there an issue with clean installing Mojave on T2 MBPs?
 

50cc

macrumors newbie
Nov 18, 2018
3
0
I did a full re-install and erase, but could not repartition the disk using the disk util in rescue mode
 

HenryAZ

macrumors 6502a
Jan 9, 2010
605
97
South Congress AZ
OP:
2. Open Disk Utility
3. In DU's upper-left-hand corner, there is a popup menu with the choice to "show all devices". That's the choice you want.
...
5. Click the Erase button and choose Mac OS extended with journaling enabled. This will be automatically converted to APFS during the Mojave install.
It's been a few weeks since I did this, but I don't believe the "Erase" button gives you formatting options. I believe it is the "Partition" button that does. Click that, partition the entire drive, and you can then choose formatting options, like HFS+.