How to get all hardlinks to the same data?

Question

Have several hardlinks to the same file.
How (for example) by one file(hardlink) get others pointing to the same data?
No real task. Just interesting. May be useful.

Answer 1

Most filesystems do not maintain a directory of where the hardlinks to a file (or more precisely, to an indode) are.

So you'll have to scan the whole filesystem to find all hardlinks. You can do this using find -inum <inode number>.

Example:

Create file with link:

$ ~> mkdir linktest
$ ~> cd linktest/
$ ~/linktest> touch file1
$ ~/linktest> ln file1 file2

Check inodes:

$ ~/linktest> stat file*
  File: file1
  Size: 0               Blocks: 0          IO Block: 4096   regular empty file
Device: 805h/2053d      Inode: 37          Links: 2
[...]
  File: file2
  Size: 0               Blocks: 0          IO Block: 4096   regular empty file
Device: 805h/2053d      Inode: 37          Links: 2
[...]

As you can see, both file entries have the same inode (37) - because they are hardlinks to the same data.

Find by inode number:

$ ~/linktest> find -inum 37
./file1
./file2

This is on Linux, but it should work the same on *BSD.

Answer 2

find has an option -samefile for this:

find / -xdev -samefile /myfile

Replace / with the root of the filesystem that myfile is on – for example, if you used /home/sergey/myfile and you have /home on a separate filesystem, then use find /home.