Find all hard links to a.txt in current directory:
find -xdev -samefile a.txt
Display the inode number of a.txt:
ls -i a.txt
Find all files (mutual hard links) with the same inode number 2000 in current directory:
find -xdev -inum 2000
-xdev means not descending directories on other filesystems. Omit it if you’re sure the operation is performed on a single filesystem.