In *BSD you can use fsdb to link an inode to a directory, ala:

    -# fsdb /dev/ufs/foo
    > inode 424242 # inode number of the target directory
    > ln 821339 myimportantfile

You might also need to do "inode 821339" and "uplink" to increment the link count. Alas, you can't do this on a live filesystem, at least not safely, and once deleted the inode will be cleared, so doing this won't get your file back. Maybe if you pull the plug and try it on an unclean filesystem?

Can you use 821339 as the target to ln? (Sadly I'm on Windows right now... work... and can't really experiment.)

i.e. -> ln 821339 new-file-name

no, unforunately not, I hoped for that too, but it seems that ln does not have any documented feature that would do that.

Effectively all ln does is call the 'link' system call, the paramters of 'link' are two path names on the same file system.

Could you not just hardlink to the /proc/<xxx>/fd/<y> file descriptor? I haven't tried this, but considering you can `cp` from the open descriptor to a new file, I should also think you could make a new hardlink to that same descriptor.

/proc is its own filesystem so its 'inodes' are incompatible with whatever FS your disk is on.

Good catch. My hardcore Unix-fu is still lacking in places... =\

whoops, sorry, on crack. You can't after it's been deleted.

It shouldn't be too hard to come up with a kernel extension that allows you to do this - in fact I wouldn't be surprised if there already was an undocumented ioctl() that links a particular inode on a file system.

Alternatively, the sledgehammer method is hitting the power button: a fsck should be able to pick up the nonzero refcount and make it available in lost+found. (depending on the file system)