I've wondered about that. It's obviously true if you make any corrections to the filesystem, and I've seen the warning. But what can go wrong if you fsck a filesystem and leave it undisturbed?
If a filesystem is mounted, it won't have the clean bit on right? Not until it's not live anymore.
Seems correct. But then the question is: what's the harm in marking a filesystem as dirty when in fact it's clean?
Interesting. You're asking if fsck checking the filesystem itself intrusive or not? That's an interesting question. We don't do it because there's no point in it really. It will freak out thinking it's not clean and try to fix it or ask us to fix it. In fact I believe some Solaris versions just won't do it and error out since the FS is mounted . But it is an interesting academic question. I vote that you try it and tell us what happens :D I'm guessing that it's still a bad idea. Since it expects the filesystem to be unmounted it may do some intrusive checks. Just a guess.