Resolved Please put me out of my misery – trying to clean install Catalina on MBA 11"

[pullman]

I recently scored a like-new maxed-out BTO/CTO 11" Macbook Air 11-inch (early 2015) and would like to clean install Catalina. But I'm not sure how to do it.

There's currently a Big Sur install on it which looks like this in Disk Utility when booted from the bootable Catalina USB:

APPLE SSD 500GB
-Container disk1
---disk1s5 (greyed out)
---Macintosh HD
---Update

I'd like to completely wipe the SSD, but when I try to erase the APPLE SSD 500GB nothing happens when I click Erase in the dialog box. The same happens when I try to erase Container disk1. It doesn't matter if I select APFS or Mac OS Extended.

Thanks in advance for your thoughts on this conundrum.

Philip

 

[Heat_Fan89]

Yeah macOS won't let you do that because it's the bootable drive. You need to boot off an external drive before it allows you to do that. You'll need to download Catalina and create a bootable flash drive. Then once you boot from that drive you'll be able to launch Disk Utility and that's when you can erase the OS partition and Data partition.

Click on this link to download Catalina then have ready a USB thumb drive preferably 16GB. Then boot from the drive.

How to download and install macOS - Apple Support

Download and install current or previous versions of the Mac operating system on compatible Mac computers.

support.apple.com

 

[saudor]

OP seem to already be booting off external USB .Try clicking on the Apple SSD at the top level and hitting erase. It will re-create the APFS structures. The APFS in BS is not really backwards compatible so you cant just erase it.

Personally I use high sierra to do this erase since well.. i havent updated my “rescue disk”. Might be an option of the cat installer is not cooperating. You can also use diskutil from terminal but that’s more involved

 

[Hombre53]

I use the High Sierra external USB (recovery disk) also to format or partition a Big Sur created drive. It works.

 

[pullman]

Thank you very much everyone for your suggestions, I'm very grateful. Yes I booted off the Catalina installer USB so it surprised me that I couldn't erase any of the various levels in that drive/volume tree. I'm wondering if it had something to do with

In the end I booted into Target Disk Mode and erased the SSD from my Mac Pro. Then I could install Catalina. First impressions are good. It runs fast and stable. Btw, Big Sur was really very slow in comparison, and also much larger on-disk I seem to remember.

Again thank you for your help
Philip

Yeah macOS won't let you do that because it's the bootable drive. You need to boot off an external drive before it allows you to do that. You'll need to download Catalina and create a bootable flash drive. Then once you boot from that drive you'll be able to launch Disk Utility and that's when you can erase the OS partition and Data partition.

Click on this link to download Catalina then have ready a USB thumb drive preferably 16GB. Then boot from the drive.

How to download and install macOS - Apple Support

Download and install current or previous versions of the Mac operating system on compatible Mac computers.

support.apple.com

OP seem to already be booting off external USB .Try clicking on the Apple SSD at the top level and hitting erase. It will re-create the APFS structures. The APFS in BS is not really backwards compatible so you cant just erase it.

Personally I use high sierra to do this erase since well.. i havent updated my “rescue disk”. Might be an option of the cat installer is not cooperating. You can also use diskutil from terminal but that’s more involved

I use the High Sierra external USB (recovery disk) also to format or partition a Big Sur created drive. It works.

 

[MBAir2010]

I would like to mention that Catalina works when the drive format is APFS, not Mac Journaled.
BigSur does not like intel chips and earlier MacBooks as I found out as well weeks ago.
Catalina is very clean and responsive, but has that annoying password entry just on deleting files and using an iPad.

 

[Jack Neill]

I would like to mention that Catalina works when the drive format is APFS, not Mac Journaled.
BigSur does not like intel chips and earlier MacBooks as I found out as well weeks ago.
Catalina is very clean and responsive, but has that annoying password entry just on deleting files and using an iPad.

Big Sur works fine on Intel Macs as long as you have a Metal GPU.

 

[Jack Neill]

I recently scored a like-new maxed-out BTO/CTO 11" Macbook Air 11-inch (early 2015) and would like to clean install Catalina. But I'm not sure how to do it.

There's currently a Big Sur install on it which looks like this in Disk Utility when booted from the bootable Catalina USB:

APPLE SSD 500GB
-Container disk1
---disk1s5 (greyed out)
---Macintosh HD
---Update

I'd like to completely wipe the SSD, but when I try to erase the APPLE SSD 500GB nothing happens when I click Erase in the dialog box. The same happens when I try to erase Container disk1. It doesn't matter if I select APFS or Mac OS Extended.

Thanks in advance for your thoughts on this conundrum.

Philip

Ive had that problem with disk utility before. I have solved it by partitioning it or by deleting containers one by one.

 

[Hombre53]

You need to boot into a USB recovery drive so that you can access disk utilities, preferably, Catalina. Do you have a USB recovery drive (Catalina)? When in disk utilities, make sure you click on "View" and select "Show All Devices". Select the main root drive (at the top). Erase the drive, select "Guid Partition Map" and then "APFS". Once successful, install macOS Catalina. This assumes you are using the Catalina USB boot recovery disk I mentioned above. Use this link to download Catalina and create a USB recovery drive: https://support.apple.com/en-us/HT201372

 

[pullman]

You need to boot into a USB recovery drive so that you can access disk utilities, preferably, Catalina. Do you have a USB recovery drive (Catalina)? When in disk utilities, make sure you click on "View" and select "Show All Devices". Select the main root drive (at the top). Erase the drive, select "Guid Partition Map" and then "APFS". Once successful, install macOS Catalina. This assumes you are using the Catalina USB boot recovery disk I mentioned above. Use this link to download Catalina and create a USB recovery drive: https://support.apple.com/en-us/HT201372

Thank you for your reply. I have in the meantime sorted this out by erasing the SSD using target disk mode.

 

[jowaju]

Just for the record, the problem you were having was due to SIP being enabled. For some reason, some (lots) of the time, a Catalina booted USB installer will have greyed out drives and will NOT allow changing/deleting/creating partitions. You may also get Disk Dissenter errors when trying to do any of those in Disk Utility. The fix for this 100% of the time is to boot to Recovery, disable SIP (csrutil disable), then boot to the Catalina Installer USB again and proceed as normal. Another tip - run csrutil disable EVEN IF it already says disabled when you type csrutil status, I have personally witnessed this, it's definitely NOT disabled, so just run the disable command and reboot.

 

[pullman]

Just for the record, the problem you were having was due to SIP being enabled. For some reason, some (lots) of the time, a Catalina booted USB installer will have greyed out drives and will NOT allow changing/deleting/creating partitions. You may also get Disk Dissenter errors when trying to do any of those in Disk Utility. The fix for this 100% of the time is to boot to Recovery, disable SIP (csrutil disable), then boot to the Catalina Installer USB again and proceed as normal. Another tip - run csrutil disable EVEN IF it already says disabled when you type csrutil status, I have personally witnessed this, it's definitely NOT disabled, so just run the disable command and reboot.

Thank you very much, that's good to know for the future.