Firmware upgrade
Login into ASA (SSH or serial port)
Provide 'enable' password
enable
Prepare files on TFTP server.
ping 192.168.74.128
copy tftp: disk0:
dir
Perform change of booting image
show version
configure terminal
dir
boot system disk0:/asa845-k8.bin
exit
write memory
show run | include boot
show bootvar
reload
show version