It is quite possible when using the FreePBX Distro that you retain 'root' CLI access to a PBX, but lost or forgot the 'admin' web interface password.

Here we reset the GUI 'admin' password from a 'root' CLI (omit the brackets):

mysql -D asterisk -u root -p<MysqlRootPassword> -e "UPDATE ampusers SET password_sha1='echo -n <NewAdminPassword>|sha1sum|cut -d ' ' -f 1' WHERE username='admin' "