Clean installing and erase - Stupid question…

[micqo]

Hi all, Sorry, this might sound stupid question... I'm laughing myself here but I need to ask… … you know that feeling that you're little bit tired/confused after messing hours with MacBook.

I clean installed HS from the usb with opt-alt key. Before that I Internet recovery Sierra, witch came with this Mac using shift + option + command + r.

Installing Sierra I erase my disk APPLE SSD… which erased also my Macintosh HD volume successfully. After installation successfully end, I booted the usb HS installer with opt-alt key, went to disk utility, and try to erase my APPLE SSD… on Internal, erasing APPLE SSD... gave me an unmount error.

I think the reason was/is because the installing process was running, and its not possible to to erase the APPLE SSD… because HS is currently running installing process, right? It should and it has to always install/erase Macintosh HD when you're installing macOS the first time, right?

Let's say that if I now boot with command + r. I am able to erase APPLE SSD..., and all disks (Macintosh HD etc) because I'm doing re-install - not new install the first time, right?

I think/I know the answer - I just want someone confirm that I'm right.

Ps. I usually always choosing Macintosh HD when clean installing and erasing. This time I'm not sure why I tried to erase APPLE SSD… disk when High Sierra was running from the usb, maybe too tired…maybe because I did it just before when installing Sierra.

 

[micqo]

Anyone/someone?

 

[hwojtek]

The Install and the Disk Utility do not run concurrently, so no, it was not the case of a disk being busy with the install.

It was just an odd unmount problem, happens from time to time. Exiting DU and launching it again to unmount the drive would perfectly do and has nothing to do with the install method (be it a bootable install media or internet recovery).

I have absolutely no idea why'd you first installed Sierra, only to upgrade it to High Sierra, but OK, perhaps you wanted to download the HS installer.
If you install from a bootable install media or internet recovery, the installer gives you a choice to whether clean install or reinstall: by means of using the Disk Utility to erase the target volume or repartition the target disk - or not using it and just upgrading.

Obviously, if there is nothing on the disk, it doesn't make any difference if you ran the DU or not.

BTW what you did is: repartitioning the physical disk APPLE SSD or erasing the Macintosh HD volume.

So what is actually your question?

 

[micqo]

Thanks for the answer.

I have always thought that install/erase method is different when booting usb and/or installing MacOS because I readed once something that it’s not possible to erase the disk booted from. Obviously this means something else and I haven’t understand all.

So if it was a unmount bug. Should i worried, erase/install again, or Can I just use my Mac? Just thinking... I have one odd issue. If I ran first aid (FileVault is enabled) my finder will corrupt and files will disappear. Don’t know is the bug on FileVault or disk utility or both.

You wonder why I install Sierra. Because HS was installed. That’s why.

 

[hwojtek]

Once you boot from the recovery partition, you may do whatever you please with the disk (even repartition it, the recovery partition will be kept intact). No matter what the boot medium (recovery, bootable installer, external disk, you name it) the process is exactly the same.
The one minor difference is, that when booting from recovery, you'd be only able to install the same MacOS version that your recovery partition has been created with - albeit since the install files will be downloaded (and it will take eternity anyway), you'll find yourself installing the latest available version of this OS.

 

[micqo]

Thanks mate! This clarified a lot

Obviously I can just ignore that unmount bug.