[solved] ln / cp / mv / samba share incremental backups

Question

Modifying a hardlink(/ed file)... argh.
Result A, old file 1 stays:
1 && echo 2 > 2 && ln 2 3 && mv 1 3 && cat 2 3 && rm 1 2 3
2
1
rm: cannot remove ‘1’: No such file or directory
Result B, file 1 gets overwritten too:
$ echo 1 > 1 && echo 2 > 2 && ln 2 3 && cp 1 3 && cat 2 3 && rm 1 2 3
1
1
Why?
I guess something like: "Because cp just overwrites the file that is where the hardlink points to while mv has to delete the hardlink first and then move the pointer thingy of the existing file"?
On a samba share, when a windows client overwrites hardlinks, I get Result B: The old file stays. Which makes for a great super easy / "lightweight" automatic incremental backup drive: I just hardlink explicitly everything to a file with the name of the current date every day and the old backup hardlinks will never be overwritten when the windows client synchronizes to the "current-directory". Or something like that...
I'm confused though as to WHY that works. Should it be working this way / can I trust that it'll keep working like that? Or is the windows client doing something "wrong" (like deleting the hardlink before copying over the modified file with the same link instead of copying it to the new destination)?
Someone please throw the manual that I need to eat to become less confused at me.
Thanks!
Last edited by whoops (2012-11-04 23:54:39)

Answer 1

Mostly I was looking for my brain, I guess
Thanks, stuff is starting to make sense now and google just got a lot more helpful than it was before, too!
That should explain what my problem was (also it offers an explanation):
http://serverfault.com/questions/225211 … -behaviour