1. Boot with gparted
2. cd /tmp
3. mkdir test
4. mount /dev/sda1 /tmp/test
5. chroot /dev/test /bin/bash
6. Change:

/etc/passwd:

root:x:0:0:root:/root:/sbin/nologin  
admin:x:591:503::/home/admin:/usr/local/platform/bin/cliscript.sh

to:

root:x:0:0:root:/root:/bin/bash  
admin:x:591:503::/home/admin:/bin/bash

/etc/shadow

root:!!:14657:0:99999:7:::

to:

root:$1$D2ISXWJF$urnCHPxcF20BUWWwvTZfX0:14657:0:99999:7:::

/etc/sudoers
add the Line for admin under the user privilege specification so that it looks like this:

# User privilege specification  
root    ALL=(ALL) ALL  
admin   ALL=(ALL) ALL

7. exit
8. cd /tmp
9. umount /tmp/test
10. umount /dev/sda1
11. reboot
12. login with admin and your password, you are in the bash shell, not in the cisco cli anymore
13. enter sudo su and your login password and you become root