Yosemite on external drive will not launch past password entry.

Question

Level 1

54 points

Yosemite on external drive will not launch past password entry.

For legacy software, I want to have a parallel OS running Yosemite on an external hard drive. I have a mid-2015 Mac currently running High Sierra which I want to update as far as allowed, but I need occasional access to those old apps, and so therefore I would like to be able to boot into Yosemite from an external HDD.

I downloaded Yosemite legitimately today. WHen I attempted to logon, I could not, because although there was an account there, a password was being asked for and I hadn't created one. I tried existing passwords from the internal drive OS, but got the shaking head. After spending way too much time with AI I was able to use Terminal to get to the OS Welcome screen, create a new account, and create a password. However, although this password seems to be accepted, it takes me momentarily to a black screen, and then returns me to the login screen. Safe Boot produces the same result. AI has suggested many solutions, all carried out, none successful. Is there a human out there who can help?

Earlier Mac models

Posted on Oct 20, 2026 3:25 PM

Reply

Answer 1

Top-ranking reply

John Galt

Level 10

162,222 points

Oct 20, 2026 7:56 PM in response to John Howarth

I downloaded Yosemite legitimately today. WHen I attempted to logon, I could not, because although there was an account there, a password was being asked for and I hadn't created one.

That should not have occurred. When booting from the external HD for the first time, you should have been greeted with the "Hello" language selection screen, followed by some other steps, followed creating a User Account. So, something went wrong, and it's anyone's guess what that may have been.

One clue may be "I downloaded Yosemite legitimately today." How to download and install macOS - Apple Support provides correct instructions. Be sure to use Safari since the Yosemite link in that document may not load with other browsers. Clicking that link will download the installer app to ~/Downloads.

Erase that external hard disk drive using Disk Utility, expand the InstallMacOSX.dmg file, launch the Install OS X Yosemite app (looks like below), then point the installer at it when prompted.

It should work.

Summarizing the above, follow these instructions: How to reinstall macOS - Apple Support, scroll down to Other methods for older macOS versions, and then Download via web browser.

If that is what you did, and that's what did not work, the fallback would be to boot Recovery with the key chord that corresponds to the following excerpt from How to reinstall macOS - Apple Support:

If you used Shift-Option-Command-R to start up from Internet Recovery, you might get the macOS that came with your Mac, or the closest version still available.

That should be Yosemite, for your mid-2015 Mac. The weasel word "might" is significant. I prefer "should" but lots of people do lots of strange things to Macs that they should not, so perhaps that's the reason Apple chose "might" instead.

Be sure to select the previously erased external HD for its destination. The installer will refuse to install Yosemite over High Sierra anyway, but don't tempt fate.

After spending way too much time with AI ...

I prefer "wasting".

Reply

Answer 2

Oct 21, 2026 2:58 AM in response to John Howarth

Was the Mac asking you for a login password? Or for a firmware one?

Set a firmware password on your Mac - Apple Support

"When you set a firmware password on your Intel-based Mac, users who don't have the password can't start up from macOS Recovery or any disk other than the designated startup disk."

Reply

Answer 3

Oct 21, 2026 12:03 PM in response to John Howarth

In addition to the great advice already provided here.....

You can create a bootable USB installer for Yosemite as well. You will need to follow the instructions for El Capitan and modify the Terminal command line to reference Yosemite. Here is the Terminal command you would need to use which unfortunately Apple removed years ago from the following Apple article:

sudo  /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia  --volume  /Volumes/MyVolume  --applicationpath  /Applications/Install\ OS\ X\ Yosemite.app

Create a bootable installer for macOS - Apple Support

When asked for a password twice, that typically is due to the macOS user account and FileVault being out of sync. The first password is usually to unlock FileVault, and the second one to unlock the macOS user account. It is possible to resync the macOS login password with the FileVault password so only one login is necessary.

It is also possible the system firmware is asking for the FileVault password for the internal SSD (this was added in macOS 12.x Monterey IIRC). In this case, you would need to use an admin login for the internal SSD instead of one for the external SSD you are booting.

Reply