Dtyjlui

i am very user of ubuntu, i have forgot my user & root's passwords now i am not able to login in my machine. I can login via guest user. please help me to reset password.

I tried to reset the password by recovery but after 3 steps. it starts asking me for "give root password for maintenance or press control-D".

I tried with another method by pressing "e" instead of "enter" by selecting ubuntu, with linux 4.4.0-140-generic (recovery mode). But the next window something very much different.

please help !

Boot from a USB (or CD/DVD if you have a system that old).

You can then mount the partition with /etc/shadow and put a new password hash in. The easiest way to do that is copy from an existing shadow file for the user (root in this case).

1. Start your machine in recovery mode -> resume normal boot. You should get a prompt with root. You need follow this steps:

root@demo:~$ mount -o remount,rw /



root@demo:~$ passwd yourusername

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully



root@demo:~$ reboot

2. You can use chroot.
Start your machine with Live CD/DVD/USB

Start a terminal and mount your root disk like following steps

# check what is your disk 

ubuntu@demo:~$ sudo fdisk -l



Disk /dev/sda: 111,8 GiB, 120034123776 bytes, 234441648 sectors

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disklabel type: gpt

Disk identifier: 083E1E28-FEE5-4BF0-B7CE-84520FB93B9D



Disposit.     Start     Final  Sectores  Size Tipo

/dev/sda1      2048    391167    389120  190M EFI System

/dev/sda2    391168  58660699  58269532 27,8G Linux filesystem

/dev/sda3  58660864 234440703 175779840 83,8G Linux filesystem



# in this case my root disk is /dev/sda2 

ubuntu@demo:~$ mkdir disk

ubuntu@demo:~$ sudo mount /dev/sda2 disk



# you can check the files for ensure is root partition

ubuntu@demo:~$ sudo ls disk 

bin    dev    home        lib     media  proc  sbin  sys  var

boot   initrd.img      lib64      mnt    root  snap  tmp  vmlinuz

cdrom  etc    initrd.img.old  lost+found  opt    run   srv   usr  vmlinuz.old



ubuntu@demo:~$ sudo chroot disk 





# passwd for your username

root@demo_chroot:~$ passwd yourusername

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully





#exit from chroot

root@demo_chroot:~$ exit



# finish umounting and reboot

ubuntu@demo:~$ sudo umount disk