I was trying to reinstall macOS Sierra in preparation for selling it. When it was about to finish it shown me " About - 405 seconds remaining".
This is a late 2015 iMac with Sierra.
[Re-Titled by Moderator]
iMac 24″, macOS 14.6
Patience can be conditional.
You will need a minimum of about 25 GB of free space on that recipient drive for any macOS installation. Disconnect any peripheral devices except the display, keyboard, and mouse before [re]installation. If you previously had a later (e.g. Catalina +) operating system installed, its APFS formatting would be unknown to Sierra, and you would have to reformat the drive as case-insensitive HFS+ (journaled).
If you have booted into Recovery and expected to download Sierra from Apple's Servers, that may not work any longer and you would need a bootable USB stick¹ built by downloading macOS Sierra from How to download and install macOS - Apple Support. I would use Safari for that download.
¹ Apple shows the procedure for High Sierra, but not Sierra. I presume the steps for High Sierra would also be acceptible for Sierra.
Note: a mid-2015 iMac originally shipped with macOS 10.10.2 (Yosemite) and a Late-2015 iMac shipped with macOS 10.11 (El Capitan). Your installing Sierra would be incorrect to prepare that 2015 iMac for resale as it should be prepped with the operating system that originally shipped on that model.
Patience can be conditional.
You will need a minimum of about 25 GB of free space on that recipient drive for any macOS installation. Disconnect any peripheral devices except the display, keyboard, and mouse before [re]installation. If you previously had a later (e.g. Catalina +) operating system installed, its APFS formatting would be unknown to Sierra, and you would have to reformat the drive as case-insensitive HFS+ (journaled).
If you have booted into Recovery and expected to download Sierra from Apple's Servers, that may not work any longer and you would need a bootable USB stick¹ built by downloading macOS Sierra from How to download and install macOS - Apple Support. I would use Safari for that download.
¹ Apple shows the procedure for High Sierra, but not Sierra. I presume the steps for High Sierra would also be acceptible for Sierra.
Note: a mid-2015 iMac originally shipped with macOS 10.10.2 (Yosemite) and a Late-2015 iMac shipped with macOS 10.11 (El Capitan). Your installing Sierra would be incorrect to prepare that 2015 iMac for resale as it should be prepped with the operating system that originally shipped on that model.
Thanks.
So I should be patient in trying over and over again, or give longer to each try?
Provided there are no other obvious issues with the controlling installation process, there is nothing to be done other than work on your patience. If that 2015 iMac has a lethargic Fusion drive, it will take longer for the installation than you have patience… 😎
I would have booted into Recovery on that Mac and run Disk Utility First Aid to ensure there were no drive errors before attempting to perform an operating system reinstallation.
How to resolve 'About - 405 seconds remaining' error during macOS Sierra reinstallation on late 2015 iMac
