Hello Lionel,
Yes, the CF is the FLASH storage for all current router models, and show flash or dir flash: commands give you the listing from the CF card.
The IOS itself is, to my best knowledge, unpacked into the RAM on all recent platforms and run from there. After the router boots up, the IOS image in the FLASH is not used anymore. The image is not opened for writing or rewritten during normal router operation. Removing and reinserting the CF card alone should be safe. In my classes, we have routinely swapped the CF cards during the router operation and we never came across a similar problem.
Situation may be slightly different if there are files opened on the CF that are rewritten in runtime - DHCP binding database, logging, etc. I do not know if IOS is using anything like a write caching (similar to Windows), however, pulling the CF card out in an unfortunate moment could result not only in incomplete file contents, but also in possibly corrupted filesystem metadata. That could in turn also cause problems even with IOS images that are not rewritten during a routine router operation.
In short, the situation is quite similar to pulling out an USB stick out of PC without properly ejecting it. Most of us do it and did not yet come to regret it, but sometimes, it can backfire. In any case, it would be helpful to see the entire message that reports the IOS corruption.
Whether the removal and reinsertion of the CF card could have caused the IOS image corruption: it is possible, but by no means certain.
Best regards,
Peter
