(Linux user? Linux only user, even? I haven't seen this information posted elsewhere, and it might be useful to others.)
1. You can do a firmware upgrade on an EOS DSLR with Linux. This assumes you have a USB card reader (highly recommended anyway). Download the Windows version of the firmware from Canon. This is actually a self-extracting Zip file, which you can unpack on Linux using the 'unzip' command. (This command is from Info-ZIP, and is probably already included in your Linux distribution.) Example:
2. You can configure settings in the camera using the "gphoto2" command. This is included in some distributions, and should be available for others, or check www.gphoto2.org. Connect camera to Linux PC using the USB cable and type "gphoto2 --list-config" to see the available settings. Change settings using "gphoto2 --set-config name=value". For example, to set the copyright text in the camera, which goes into pictures as EXIF data:
gphoto2 --set-config /main/settings/copyright="Copyright (C) Your Name Here"