Reset Password if forget username and password

Example: Reset Password

Reference model:

• Switch model name: AS7816-64X
• Edgecore SONiC version: SONiC.Edgecore-SONiC_20200116_051623_ec201904_128

Procedure :

Step 1: Reboot system and press “e” to edit SONiC grub option (e.g SONiC-OS-Edgecore-SONiC_20200116_051623_ec201904_128)

                             GNU GRUB  version 2.02

 +----------------------------------------------------------------------------+
 |*SONiC-OS-Edgecore-SONiC_20200116_051623_ec201904_128                       |
 | ONIE                                                                       |
 |                                                                            |
 |                                                                            |
 |                                                                            |
 |                                                                            |
 |                                                                            | 
 +----------------------------------------------------------------------------+

      Use the ^ and v keys to select which entry is highlighted.          
      Press enter to boot the selected OS, `e' to edit the commands       
      before booting or `c' for a command-line. 

                             GNU GRUB  version 2.02

 +----------------------------------------------------------------------------+
 |setparams 'SONiC-OS-Edgecore-SONiC_20200116_051623_ec201904_128'            | 
 |                                                                            |
 |        search --no-floppy --label --set=root SONiC-OS                      |
 |        echo    'Loading SONiC-OS OS kernel ...'                            |
 |        insmod gzio                                                         |
 |        if [ x = xxen ]; then insmod xzio; insmod lzopio; fi                |
 |        insmod part_msdos                                                   |
 |        insmod ext2                                                         |
 |        linux   /image-Edgecore-SONiC_20200116_051623_ec201904_128/boot/vml\|
 |inuz-4.9.0-9-2-amd64 root=/dev/sda4 rw console=tty0 console=ttyS0,115200n8 \|
 |quiet                  net.ifnames=0 biosdevname=0                 loop=ima\|
 |ge-Edgecore-SONiC_20200116_051623_ec201904_128/fs.squashfs loopfstype=squas\|v
 +----------------------------------------------------------------------------+

      Minimum Emacs-like screen editing is supported. TAB lists           
      completions. Press Ctrl-x or F10 to boot, Ctrl-c or F2 for          
      a command-line or ESC to discard edits and return to the GRUB menu.   

Step 2: Add init=/bin/bash as shown below, 

  +----------------------------------------------------------------------------+
 |        insmod gzio                                                         |^
 |        if [ x = xxen ]; then insmod xzio; insmod lzopio; fi                |
 |        insmod part_msdos                                                   |
 |        insmod ext2                                                         |
 |        linux   /image-Edgecore-SONiC_20200116_051623_ec201904_128/boot/vml\|
 |inuz-4.9.0-9-2-amd64 root=/dev/sda4 rw console=tty0 console=ttyS0,115200n8 \|
 |init=/bin/bash quiet                  net.ifnames=0 biosdevname=0          \|
 |       loop=image-Edgecore-SONiC_20200116_051623_ec201904_128/fs.squashfs l\|
 |oopfstype=squashfs                                       apparmor=1 securit\|
 |y=apparmor varlog_size=4096 usbcore.autosuspend=-1 tg3.short_preamble=1 tg3\|
 |.bcm5718s_reset=1                                                           |
 |        echo    'Loading SONiC-OS OS initial ramdisk ...'                   |v
 +----------------------------------------------------------------------------+

      Minimum Emacs-like screen editing is supported. TAB lists           
      completions. Press Ctrl-x or F10 to boot, Ctrl-c or F2 for          
      a command-line or ESC to discard edits and return to the GRUB menu.  

Note: This insertion will be restored after rebooting. Therefore, it's not necessary to edit grub option again.

Step 3: Press Ctrl+x to boot

Loading SONiC-OS OS kernel ...
Loading SONiC-OS OS initial ramdisk ...
[ 2.708038] irq 16: nobody cared (try booting with the "irqpoll" option)
[ 2.714804] handlers:
[ 2.717210] [<ffffffff94c427b0>] serial8250_interrupt
[ 2.722539] Disabling IRQ #16
[ 3.647833] ixgbe 0000:08:00.1: HW Init failed: -17
bash: cannot set terminal process group (-1): Inappropriate ioctl for device
bash: no job control in this shell
root@(none):/#

Step 4: Now you're able to modify the password by linux command.  Username root as example. 

root@(none):/# passwd root
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Step 5: Reboot the switch by linux command or Power cycle the switch

root@(none):/# reboot -f

Reference: SONiC Github https://github.com/Azure/SONiC/blob/master/doc/SONiC-User-Manual.md#23-how-to-reset-password