Question

In a knopix enable to access another drive because i forgot the password how to recover that password or change password.

Answer 1

When booting, press any key at the GRUB menu and highlight the kernel of your choice. Press e on the selected kernel to append to it's boot options, and enter single at the end of the line. Press Enter and then b to boot into single user mode. It will leave you at a sh prompt where you can then use the passwd command to change your password.

example:

sh-3.2# passwd john
Changing password for john
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
sh-3.2#

as you can see, it will not prompt you for your previous password.

Answer 2

John T's suggestion to enter single user mode is the safest thing to try first. If that's not sorking for you, and depending on your configuration, you may want to check out this page, giving a variety of approaches.