Root password recovery via console

Hello Community,

One of our F5 devices got to hung state after /var got 100%. I am not able to access the device via GUI and tacacs/root passwords not working via CLI. Device is up and reachable. So, i connected F5 console via RJ45 to a console server. From console server i tried to access F5 and getting login page. But when i try a reboot for password recovery i am not seeing boot page or GRUB option. (steps : Restarting the BIG-IP system in single-user mode (GRUB 0.97) (f5.com))

Please let me know if Connecting console via RJ45 will not help in this console process or not. 

console prompt once F5 done reboot. I am not getting physical support for do serial connection via laptop.so we done RJ45 connection to console server(Raritan).