Admin Account Has Gone

I purchased the clean my Mac 3 software ...

"Cleaning" apps are scams. Excerpted from Effective defenses against malware and other threats:

Never install any product that claims to "clean up", "speed up", "optimize", "boost" or "accelerate" your Mac; to "wash" it, "tune" it, or to make it "shiny". Those claims are absurd.

• Such products are very aggressively marketed. They are all scams.
• They generally operate on the flawed premise that a Mac accumulates "junk" that needs to be routinely "cleaned out" for optimum performance.
• Trial versions of those programs are successful because they provide the instant gratification of greater free disk space.
• That increased space is the result of irreversible destruction of files, programs, or operating system components normally protected from inadvertent alteration or deletion. The eventual result will be unreliable operation, poor performance and random crashes that may not become evident for months or even years after their use, when updates to programs or OS X are eventually released.
• Memory "cleaners" that circumvent OS X's memory management algorithms work by purging inactive memory contents to mass storage, which can only result in degraded performance and accelerated hardware failure.

To remove CleanMyMac 3 itself, use its Uninstaller module, followed by these additional steps:

Remove the file ~/Library/LaunchAgents/com.macpaw.CleanMyMac3.Scheduler.plist

• To navigate to that file, copy and paste the following line into the Finder's Go menu > Go To Folder...

~/Library/LaunchAgents/

com.macpaw.CleanMyMac3.Scheduler.plist

• Then, open  (Apple menu) > System Preferences > Users & Groups > Login Items.
• Select the item CleanMyMac3 Menu
• Click the [—] (minus) button.
• Restart your Mac.

Beware that reinstalling OS X alone will have no effect on either removing CleanMyMac or reversing the damage it is capable of inflicting upon a system. To recover from the effects of having used it to modify OS X / Sierra, the additional software you require and the essential files you need, follow the applicable recovery procedure below:

• If you have a backup that you created prior to using CleanMyMac, now is the time to use it. For Time Machine, boot macOS Recovery, and at the Mac OS X Utilities screen, choose Restore from Time Machine Backup. Choose a date preceding the installation of CleanMyMac.
• If you do not have a backup that predates the use of CleanMyMac, create one now. To do that read Use Time Machine to back up or restore your Mac.
  • The recovery procedure will require that you erase the Mac using OS X Recovery, and then create a new User Account whose contents will be empty. You will then be able to use Setup Assistant to migrate your essential documents including photos, music, work products and other essential files.
  • To erase and install OS X read How to reinstall macOS on your Mac.
    • Follow Step 2 to completely erase that Mac's internal storage: Erase a volume using Disk Utility.
    • Then, follow the procedure in Move your content to a new Mac.
    • When asked how you want to transfer your information, select Transfer from a Mac, Time Machine backup, or startup disk.
    • Under Select the Information to Transfer, select only your previous User account and do not select "Applications", "Computer and Network Settings" or "Other files and folders". De-select those choices.
  • Subsequent to using Setup Assistant, you will need to reinstall the essential software you may require, once again remembering to install software only from their original sources, and omitting all non-essential software.
  • "Non-essential software" is a broad category that includes but is not limited to third party "cleaning", "maintenance", and "anti-virus" products.

Totally agree on Cream My Mac.

You need a space between ls & /users

Follow these instructions: How to reinstall macOS on your Mac.

I think that command only shows logged in users normally, try...

http://ajmccluskey.com/2015/01/managing-users-and-groups-from-the-os-x-terminal/

As I understand it, you have a Mac with no Administrator accounts. Of course that is not supposed to be possible, but the various "cleaning" apps work at privileged levels capable of limitless destruction. It may still be required to erase that Mac completely and reconfigure it as if it were new... the eventual result of using them.

You may be able to use the following technique to create a new, temporary Administrator account, the sole purpose of which will be to log in, create a backup, and eventually retrieve your normal User Account.

There are several caveats:

• The problem you originally encountered may have been an indication that your Mac's startup volume was already in a failed state.

  If that is the case, it should be replaced and its contents restored from a Time Machine or equivalent backup, which I understand was never created.

• It may not work with El Capitan and I no longer have any El Capitan installations with which to verify this procedure.
• It will not work in the following circumstances:
  • If you configured an EFI Firmware Password, unless you know that password.
  • If you encrypted your startup volume with FileVault.

Please read everything that follows before continuing. If you have only the one computer you will need to print this for reference.

• Power on or restart your Mac.
• At the chime or grey screen, hold ⌘ and S on your keyboard (two fingers) to enter single-user mode.
• At the localhost:/ root# prompt, type

fsck -fy

...and press Return.

This is a simple check for file system integrity and is optional. It may take a few minutes to complete during which time various messages will appear. None of them are relevant unless they indicate some unrecoverable error. Be patient. If you get concerned that the system has stalled or become unresponsive press the Return key. Nothing will happen other than to echo the Return character, advancing the text on the screen, confirming your Mac has not completely frozen. When the integrity check completes pressing the Return key will result in the localhost prompt again, waiting for your input.

• If the file system integrity check is not successful, it will conclude with an error. In that case there is no point in continuing. Contact AppleCare for repair options.
• If the file system integrity check is successful, it will return text similar to "The volume Macintosh HD appears to be OK". Assuming that's the case, continue below.
• At the localhost:/ root# prompt, type each of the following lines, exactly as written, including capitalization, one line at a time, each line followed by the Return key. There is a single space after the word mount in the first line, and preceding the first "slash" ( / ) character in each line. In other words the first line is mount space -uw space slash return:

mount -uw /

rm /var/db/.AppleSetupDone

reboot

The Mac will restart, and then take you through the entire setup and registration process that you have not seen since you originally unboxed it. Do not be concerned — none of the above deletes any information other than the hidden AppleSetupDone file whose presence indicates your Mac has been configured and is ready for use. All your pre-existing User Accounts will still available, assuming they were not already erased or corrupted prior to the start of this procedure.

Do not elect to transfer your information from another Mac: When you get to the "Do You Already Own a Mac" screen, select "Do not transfer any information now" and press Continue. Have your existing Apple ID and password ready. At the "Create a Computer Account" screen, create the new, temporary account using a different "Full name" and "Account name" than the one you already use. Remember the password you select.

When it completes, log in under that new account, and immediately create a Time Machine or equivalent backup.

Then, use System Preferences and change your normal account to "Allow user to administer this computer". Log out, log in under your normal account and verify you can use it without restriction. After that, you can safely delete the temporary account you just created.

If the above does not work for any reason, contact AppleCare: Contact Support.

The original problem was this:

I have a iMac 27 and for the last week had problems with everything running really slow. ... A few days later my computer turned of without my assistance.

When everything starts running slowly without having installed some product that could account for that degraded performance, the cause is almost always a failed hard disk drive. In that case the primary task is to ensure a reliable backup of your data exists.

Then, you can help support a suspicion of hardware failure by starting your Mac in "Safe Mode": Try safe mode if your Mac doesn't finish starting up - Apple Support. Follow all its recommendations including "If an issue doesn't happen in safe mode".

As it states "Safe Mode" performs a few tasks that might resolve certain problems on its own. Using a Mac in that mode is generally inconvenient and isn't intended to be used for any length of time. Screen redraws are clunky and jagged and certain programs just won't work, but if the performance problems remain unchanged in Safe Mode, the cause is usually a hard disk that has failed and must be replaced.

In some cases reinstalling OS X / macOS might be worth trying, but operating system corruption should not have occurred to begin with. Whatever caused that to occur would still exist and need to be addressed. Aggressively marketed, ill-conceived "cleaning" apps that claim to cure all ills are often the cause.

Worked for me but note there is no space after the / and the period and "Setup" should be "SetUp" in the last line before reboot.

John Galt, you are the man!

Thank you so so much for helping me save my 9000 odd photos