Make sure PC can ping (or contact) ASA.
Install tftpd-hpa (defaults work fine, but conf is /etc/default/tftpd-hpa)
Run it:

# /usr/sbin/in.tftpd --listen --user tftp --address --secure /var/lib/tftpboot

Copy files to /var/lib/tftpboot directory (asa831-k8.bin, adsm-631.bin etc)

Add IP of ASA to iptables.conf and run it to let traffic from the ASA through.
Example IP tables line:


Optionally test by installing tftp and tftp localhost.


# copy tftp: flash:

enter IP, source and destination file name and wait for copy
repeat for second file (IOS or ASDM)

optional verify:

# verify flash:/<file>

To install, go to global configure:

# adsm image disk0:/adsm<version>  
# boot system disk0:/asa<version>  
# copy run start  
# reload