So, first power on or reboot Debian system. It should be presented with a GRUB menu as shown below. On the first option, proceed and press the ‘e’ key on the keyboard before the system starts booting .
Scroll down and locate the line that begins with ‘linux’ that precedes the /boot/vmlinuz-* section that also specifies the UUID.
Move the cursor to the end of this line, just after ‘ro net.ifnames=0 biosdevname=0 quiet’ and append the parameter init=/bin/bash.
Next hit ctrl + x to enable it to boot in single-user mode with the root filesystem mounted with read-only (ro) access rights.
To reset the password, we need to change the access right from read-only to read-write. Therefore, run the command below to remount the root filesystem with rw attributes.
mount -n -o remount,rw /
Next, reset the root password by executing the good old passwd command as shown.
passwd
With the root password successfully changed, reboot your Debian system by Ctrl + Alt + Del .
And that’s how reset a forgotten root password on Debian.
Thankyou.