Re: Symlinks vs. hardlinks

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

tomas@tuxteam.de wrote:
> > >   tomas@rasputin:~$ ln /home/test/.profile test-profile
> > >   ln: failed to create hard link `test-profile' =>
> > > `/home/test/.profile': Operation not permitted

Seems to be a new security feature.

In "man 5 proc" i read
  "/proc/sys/fs/protected_hardlinks (since Linux 3.6)
   ...
   When the value in this file is 1, a hard
   link  can be created to a target file only if one of the follow‐
   ing conditions is true:
   ...
   *  The caller has the CAP_FOWNER capability.
   *  The filesystem UID of the process creating the link matches
      the  owner  (UID) of the target file [...]
   *  All of the following conditions are true:
      ...
      ·  the caller has  permission to read and write the target
         file
"

So it is not enough to have w-permission of the directory where
the new link shall emerge. Ownership or rw-permission of the target
file is needed, too.

The described behavior is in effect here:

  $ cat /proc/sys/fs/protected_hardlinks
  1


Have a nice day :)

Thomas