I found a empty directory called \lost+found in root directory. And I noticed that there is no such a directory in newly installed Fedora system (which use btrfs by default).
As far as I know, it is used in fsck and specific to ext2/3/4. Given that my Fedora was installed with btrfs, I’m wondering:
I don’t know where it might have come from, but it is safe to delete.
Might be indicative to checkout ls -l / | grep lost before deleting in order to find out when it has been created (or more precisely, touched). The metadata received that way can have been updated/touched after creation, but if it is not in use, it might be still indicative. Is there a chance you copy-pasted (parts of) your root file system from another installation or so?
Another explanation might be if earlier Fedora releases created such a directory while newer releases don’t (maybe someone knows off the cuff?).
I would also check if anything is contained, and if the ls -l indicates that the folder has not been touched for long. If so, I see no reason to keep it. But it of course does not hurt as well.
I found the directory has been created even before I had installed my system. So it must be created by system or copied from other places accidentally. I will delete it directly. Thanks a lot.
I found a reference and explanation to this directory here: https://www.baeldung.com/linux/lost-found-directory