How to get a list all the “aliases” of a file (including of type directory) efficiently?

Question

How can one get the list of all the aliases of a file (including of type directory) efficiently, given that a file:

1. may have multiple hard links, multipe soft links, multi-level soft links
2. may be present under a directory which is mounted at another location in the same filesystem
3. may be present under a directory that has link(s) pointing to it; again the links having features mentioned in 1

Could a possible solution be using inodes?

Answer 1

Hard links can be identified by comparing both the inode number and the device number (two different mounted file systems may each have a file with the same inode number, but they will have different device numbers). You can read the device/inode manually with stat $file, or find can do it for you with -samefile. You can make searching for hard links more efficient by searching only within the same device:

find $fsroot/. -mount -samefile $myfile

Soft links are harder as they can be located anywhere. You need to dereference them to identify the inode/device. You can do this manually with stat -L or automatically with find -L:

find -L / -samefile $myfile

Note that this will also find hard links. I don't think find has an easy way to search for only soft links that point to a specific inode.

It might be that some file-systems can tell you this information more efficiently, but I think the in the general case you need to scan every file.