Ok. You want to flash the firmware of a Cisco 1140, Cisco 1130 or any other Aironet AP. So, download here the desired image you want to install, if you haven't already done so.
To install the image we have to setup a TFTP server on our Ubuntu/Debian system. We assume you have opened a root shell. You can achieve this for example with:
$ sudo -s #
Now install the Advanced Trivial FTP server, which fits our needs best:
# apt-get install atftpd
In case inetd or aftpd were started during the installation of aftpd, you have to stop these services now:
# service inetd stop # service atftpd stop
Configure your network adapter for the additional subnet 10.0.0.0/31, assuming your network adapter is eth0. Pay attention to other subnets on your computer, that there are no conflicts.
# ifconfig eth0:1 10.0.0.2 netmask 255.255.255.252
Create at tftp boot folder, and if you already know the filename of the firmware your access point expects, copy the downloaded firmware to the /tftpboot folder giving it the expected name.
# mkdir /tftpboot # cp firmware_downloaded /tftpboot/filename_acceesspoint_expects
Start the TFTP server on the command line in foreground:
atftpd --bind-address 255.255.255.255 --daemon --no-fork --logfile - /tftpboot
Now power on your access point, while pressing and holding the mode button until the led lights amber being steady on. After awhile you should notice some action on the TFTP server.
root@bib:~# atftpd --bind-address 255.255.255.255 --daemon --no-fork --logfile - /tftpboot Feb 16 07:57:23 bib atftpd[1258.139650896482112]: Advanced Trivial FTP server started (0.7) Feb 16 07:58:13 bib atftpd[1258.139650874779392]: Serving c1140-k9w7-tar.default to 10.0.0.1:1024
In our example the access point tried to download a file with the name c1140-k9w7-tar.default as seen in the message "Serving c1140-k9w7-tar.default to 10.0.0.1:1024".
If there was not the desired file in the /tftpboot folder, copy now the file into the folder and repeat the procedure: turning the AP on while holding the mode button.
After that, the AP should the be flashed with new firmware.