Summary
If you have lost the root password for ECX. Please use the following 7 steps to reset the root password.
Step By Step
Step 1: Take a snapshot of the ECX host.
Step 2: Boot or Reboot your CentOS installation.
For virtual appliance, hold on Shift key once the machine is rebooted.
Step 3: Press any key to enter menu
Step 4: Select CentOS 2.6 from the Grub Menu, it should look like this
Step 5: Select Kernel Option Menu, and press <e> . it should look something like this.
Steps 6: Add Single behind the following line, then press <e> to enter to go edit the Kernel option menu.
remove "rhgb quiet" and add Single
Change it to <DTYPE=pc KEYTABLE=us rd_NO_DM Single
Press <Enter>
Step 7: You should see the "Kernel /vmlinuz-2.6.32.220.e16.x86_64 ro root..." line. Press <b> key to boot into this temporary options to allow you to reset you root password
Step 8: Set Root Password.
Now you are boot up into the root shell, you can use passwd to set your new password.
a) Type in the following command
# passwd
b) Type in your new password twice.
Once this is complete, you can reboot the machine and login with the new password.
For further information or other version of CentOS please refer to:
https://wiki.centos.org/TipsAndTricks/ResetRootPassword