Ubuntu: Resetting the root password while accessing the server console in EFI boot mode

If you need to reset a forgotten password on Ubuntu OS installed in EFI mode, follow these steps:

1. During boot, hold the "ESC" key to enter the GRUB menu. A "grub>" command prompt should appear.
   
   
2. Execute the "ls" command. The console will display available partitions, for example:
   (hd0,gpt3) (hd0,gpt2) (hd0,gpt1) (lvm/ubuntu--vg-ubuntu--lv)
   
   
3. Now, check these partitions with the commands:
   ls (hd0,gpt1)/
   ls (hd0,gpt2)/
   ls (hd0,gpt3)/
   ls (lvm/ubuntu--vg-ubuntu--lv)/
   
   You need to find:
   The System Partition - contains directories like familiar folders at its root: boot, home, usr, etc.
   The Boot Partition - contains:
   - The kernel file (vmlinuz): a file whose name starts with "vmlinuz-", e.g., "vmlinuz-6.8.0-31-generic".
   - The initrd file: a file whose name starts with "initrd.img-" and contains the same version as the kernel, e.g., "initrd.img-6.8.0-31-generic".
   Write down or remember the full names of these two files.
   
   
4. Manually set the boot commands.
   Let's assume your boot partition is "(hd0,gpt2)" and the system partition is "(lvm/ubuntu--vg-ubuntu--lv)".
   
   
5. Tell GRUB where to find the boot files (the boot partition):
   set root=(hd0,gpt2)
   
   
6. Load the kernel:
   linux /vmlinuz-6.8.0-31-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv rw init=/bin/bash
   where
   root=/dev/mapper/ubuntu--vg-ubuntu--lv - the path to the LVM volume as the root partition;
   rw - mount for writing (ro - read-only);
   init=/bin/bash - boot directly into the root shell.
   
   
7. Load the initrd image (necessary for LVM to work):
   initrd /initrd.img-6.8.0-31-generic
   
   
8. Start the boot process:
   boot
   After the OS image loads, an input prompt in the format "root@(none):/#" will appear.
   
   
9. Change the password for "root" or another user:
   passwd root
   
   
10. Perform a reboot:
    reboot -f
    
    

If boot errors occur and the "(initramfs)" input prompt appears instead of "root@(none):/#", try mounting the filesystem manually:

1. Create a mount point:
   mkdir /rootfs
   
   
2. Mount your LVM volume:
   mount /dev/mapper/ubuntu--vg-ubuntu--lv /rootfs
   
   
3. Check the mount:
   ls /rootfs
   You should see the contents of the root filesystem (/): folders like bin, home, usr, etc, etc.
   
   
4. Use the chroot command to make the mounted partition the root for subsequent commands:
   chroot /rootfs
   
   
5. Change the password for "root" or another user:
   passwd root
   Enter the new password twice.
   
   
6. Reboot the system to normal mode:
   
   Exit chroot:
   exit
   
   Unmount the partition:
   umount /rootfs
   
   Perform a reboot:
   reboot -f

Note: Make sure to use the exact kernel version and LVM path found on your system when entering the commands.