Revert 2011 MBA to El Capitan from High Sierra

[Boyd01]

Trying to remotely help a friend in the EU get her 2011 MacBook Air back to El Capitan. She is not technically inclined but very good at using computers and following directions. Unfortunately she lets her students use her computer and one of them decided to update to High Sierra, making it really slow.

I already know how to re-download El Capitan from the App Store, so that is no problem. But I have no personal experience with High Sierra or APFS (my own Macs are on Sierra and El Capitan). What will happen when she runs the El Capitan installer on her APFS SSD? Will it allow her to reformat the SSD as HFS and do a clean install? Is this all very straightforward, or is something special involved?

I'm assuming that it won't be possible to install El Capitain over High Sierra without completely wiping the SSD, so she will need to do a clean install, then use Migration Assistant to move a backup of her files to the MBA.

So, if she does a Time Machine backup to an external USB hard drive under High Sierra, will this work properly? Or will there be an El Capitan issue because the Time Machine backup was created under High Sierra? Would Carbon Copy Cloner be a better way to backup of the High Sierra machine before reverting to El Capitan?

Thanks in advance for any insights!

 

[Mr_Brightside_@]

She will need to wipe it and revert to HFS, but you could double check to be sure it was converted to APFS.

CCC would be the better backup method to use, but if it's made with High Sierra, Migration assistant likely won't be able to bring everything back to EC, items may need to be manually copied. Won't know for sure till she tries.

 

[Boyd01]

She will need to wipe it and revert to HFS, but you could double check to be sure it was converted to APFS.

Thanks! Her internal SSD is currently APFS, she already sent me a screenshot from disk utility. I assume the El Capitan installer will reformat the ssd automatically as part of the installation?

She will get an external USB hard disk to make a backup under High Sierra. Since it will be a new disk, it will probably be pre-formatted for Windows. If she uses Disk Utility, I assume that would format it as HFS. My understanding is that High Sierra does not use APFS on external hard drives. True?

So, assuming the backup is created on an HFS volume with High Sierra, is there some reason why this wouldn't be compatible with El Capitan? Mostly, it is just Microsoft Word files, she uses very little in the way of software and has an old version of MS Word. She does have an old time machine backup from 2016, so she could restore any software such as Word from that if needed.

I'm personally a big fan of Carbon Copy and use it for everything, but am trying to keep this as simple as possible for her. In what way would a CCC backup be preferable to Time Machine?

 

[Weaselboy]

@Boyd01 ... here is what I would do.

The problem here is she is trying to go back a version, so that takes Migration Assistant off the table. I think the cleanest and easiest way forward here is a wipe and install of El Capitan then manually drag and drop things back in from a CCC HFS+ external USB drive.

Option key boot to the El Capitan installer, then have her start Disk Util and select the drive itself at the very top like my red arrow there. This will wipe the entire drive, including any APFS containers. Then select the Erase button in the toolbar and format to Mac OS Extended (Journaled). That will get the drive back to one HFS+ partition.

Then install El Capitan and have her make an account. Then attach the CCC drive and drag and drop her documents back in.

MS Word cannot be dragged in like this, it will require running the MS installer and entering of registration into. If here needs are not great, maybe she can get by with the freeware OpenOffice?

 

[Boyd01]

Well that isn't as easy as I had hoped, but thanks a lot - I appreciate it! She does have a time machine backup from 2016 however, so she could restore that after installing El Capitain and then manually copy her newer documents from a CCC backup. That should restore her user account, software like Word, etc.

 

[Weaselboy]

She does have a time machine backup from 2016 however, so she could restore that after installing El Capitain and then manually copy her newer documents from a CCC backup.

That would work.... but there is a catch. You can actually option key boot to a TM backup and get to a restore screen that allows you to run Disk Util and erase then the restore puts the OS and everything right back from the backup set.

However, Apple broke that feature in El Capitan. It works in OS versions before and after El Capitan. There is a work around. She could command-option-r boot to Internet recovery and get to the recovery screen that way. Then use Disk Util to erase.... then restore. That would get her back to a spot in time in 2016 when the backup was made... OS, apps, data.... everything. Then after manually move newer data from the CCC clone.

This would save having to even create the El Capitan installer and installing the OS.