Have lost admin privileges in High Sierra.

Galt’s post on Jan 5, 2018 5:50 PMRe: Lost Administrator Accessin response to Mutant_Bunny. Briefly:

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.

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 preceding the first "slash" ( / ) character in each line:

mount -uw /

rm /var/db/.AppleSetupDone

reboot

My computer boots up fine and runs properly with the exception that every time I delete a file, or move it from my desktop to my hard drive it asks for verification, but when I try to add my name (I am the administrator) I get ‘denied, you do not have sufficient privileges” back. All that shows in the get info window are “system, wheel and everyone” and I can not change the privileges for any of the 3 entries nor add users. This really gets tedious. My correct login account is shown in System Preferences under “users and groups”. “File vault” is not activated. Have I missed something? my mid 2010 MacBook Air suffers from the same affliction and I have not detected any viruses nor malware. I am using Malwarebytes. The latest Code Warrior detects only minor defects which it fixes; the same for Disk Doctor