How can i know if un AP1240AG this in mode autonomous or mode lightweight????
The methods Leo has mentioned are good ones. Another easy way is to look at the image name in a 'show version' output. If the image name contains:
1) k9w7 - it is autonomous
2) k9w8 - it is lightweight
1. Look at the logs for any sign of the word "JOIN". If this is visible, then you are running one of the two LWAP images;
2. Look at the file being used. If the filename has "rcv" then you are using the LWAP recovery image.
3. If you are running an LWAP image (full or "rcv") you will NOT be able to save your config.