My mac doesn’t have an administrator acount and now cant do changes or update my mac

The "mount -uw /" command that frequently appears in these kinds of tutorials won't work in macOS Big Sur or later. This is because the root volume is a sealed snapshot, and cannot be modified or mounted as read-write.

In macOS Catalina, that command will also fail, because System Integrity Protection blocks the system volume from being mounted as read-write.

To delete the .AppleSetupDone file in macOS Big Sur via Single User Mode, follow these steps to mount the Data volume (which contains the file in question, and can be modified). Note that this probably won't work in macOS Catalina.

1. Start up in Single User Mode. On supported Intel-based Macs, hold down Command-S as you power on or restart your Mac. Release the keys when white text appears on a black screen. (It's technically possible to get Single User Mode on other Intel-based and/or Apple silicon Macs, but that requires setting an NVRAM variable and possibly downgrading the boot security.)
2. If you're prompted to log in first, do so to continue.
3. When the text stops moving, the command line should appear (sh-3.2). If it doesn't, press the Enter/Return key once.
4. Type the following commands in order, exactly as shown:
   1. Mount the Preboot, VM and Update volumes: mount -P 1
   2. If you're running on an Apple silicon Mac and FileVault is enabled, unlock the Data volume: apfs_unlockfv
   3. If you're running on an Apple silicon Mac, start Data Protection services: /usr/libexec/init_data_protection
   4. Mount the Data volume: mount -P 2
   5. Now that the Data volume is mounted, delete the setup file: rm /var/db/.AppleSetupDone
   6. (Nicely) Restart your Mac: launchctl reboot
5. Your Mac should now restart. If prompted to log in, do so to continue.
6. The Setup Assistant will now appear, and you'll be able to make a new admin account, which you can use to restore admin privileges to your regular account.

If Single User Mode doesn't work, there's an easier way to do this that works on basically any version of macOS. This easier method is to utilize macOS Recovery.

1. Start up in macOS Recovery.
2. If you're prompted for an administrator password, try to find some way to bypass that requirement. On T2 or Apple silicon Macs, you might have the option to authenticate via Activation Lock. If that isn't available, and FileVault is on, you might be able to retrieve your recovery key from iCloud and authenticate that way.
3. When the main utilities window appears, select Disk Utility and click Continue.
4. In the sidebar, select Macintosh HD and mount it. This might require your login password if FileVault is enabled. Also, if the name of this volume is different than Macintosh HD, take note of that.
5. If you're running macOS Catalina or later, select Macintosh HD - Data (or "Data") and mount it. This will require your login password if FileVault is enabled.
6. When done, quit Disk Utility.
7. The main utilities window should appear. At the top of the screen, select Utilities -> Terminal.
8. Type this command to delete the setup file. If the name of your startup volume is different than "Macintosh HD", replace "Macintosh HD" with the correct name: "rm /Volumes/Macintosh HD/var/db/.AppleSetupDone"
9. Restart your Mac.

See this article to create an admin account: https://www.lifewire.com/create-new-admin-account-for-login-issues-2259976

How did you setup your Mac originally without an administrative account?

See Kurt Lang's post in this topic: Admin - Apple Community

Encryptor5000 wrote:

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The Setup Assistant will now appear, and you'll be able to make a new admin account, which you can use to restore admin privileges to your regular account.

Sounds likely to succeed. Thanks.

Try the Return key. If that doesn't work, I don't know what to tell you. The instructions on the page I linked and Kurt's which are one and the same, along with any instructions I've seen should be correct.

EDIT to my steps for Single User Mode: You might need to start Data Protection services first (4.3) before unlocking the Data volume (4.2). Nonetheless, your data should still be fine even if you get the order for those two steps wrong. Also, those steps only apply to Apple silicon Macs, which can't even boot Single User Mode by default.

Mxdm_1 wrote:

https://discussions.apple.com/content/attachment/4c635bd6-d168-4a29-8aff-d449c6a17eb4

My mac has no admin account

What happens if you enter your user name and psswd?

Did you try typing in the commands after sh-3.2?