I have an external HDD and use TrueCrypt for keeping encrypted file containers. After mounting, whenever I try to dismount a file container (using TrueCrypt 7.0a on Ubuntu 11.04), it just does not happen and I get the following message:
device-mapper: remove ioctl failed: Device or resource busy Command failed
Further, if I close TrueCrypt and then try to start it again, it says that TrueCrypt is already running, but I cannot access it from the Unity sidebar (because it is not there).
Also, if I power down my external HDD, the TrueCrypt volume still shows as one of the mounted volumes, but I cannot do anything with it.
Any possible work around? I remember this NOT happening in earlier versions of Ubuntu so I am guessing there is something to do with 11.04.