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Groups > linux.debian.user > #162644

Re: Symlinks vs. hardlinks

From <tomas@tuxteam.de>
Newsgroups linux.debian.user
Subject Re: Symlinks vs. hardlinks
Date 2016-01-05 11:40 +0100
Message-ID <qNxbX-O8-9@gated-at.bofh.it> (permalink)
References <qNvjP-7VD-11@gated-at.bofh.it> <qNwIV-Cq-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, Jan 05, 2016 at 11:08:11AM +0100, Thomas Schmitt wrote:
> 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

Thank you for showing this old dog a new trick :-)

> Have a nice day :)

and a happy new year

regards
- -- tomás
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Thread

Prevent shutdown with systemctl Floris <jkfloris@dds.nl> - 2016-01-04 17:00 +0100
  Re: Prevent shutdown with systemctl Michael Biebl <biebl@debian.org> - 2016-01-04 18:20 +0100
    Re: Prevent shutdown with systemctl Floris <jkfloris@dds.nl> - 2016-01-04 20:10 +0100
      Re: Prevent shutdown with systemctl Floris <jkfloris@dds.nl> - 2016-01-04 21:00 +0100
        Re: Prevent shutdown with systemctl Michael Biebl <biebl@debian.org> - 2016-01-04 21:20 +0100
      Re: Prevent shutdown with systemctl Brian <ad44@cityscape.co.uk> - 2016-01-04 21:50 +0100
        Re: Prevent shutdown with systemctl Floris <jkfloris@dds.nl> - 2016-01-04 23:50 +0100
          Re: Prevent shutdown with systemctl Michael Biebl <biebl@debian.org> - 2016-01-05 00:50 +0100
            Re: Prevent shutdown with systemctl Brian <ad44@cityscape.co.uk> - 2016-01-05 01:30 +0100
              Re: Prevent shutdown with systemctl Michael Biebl <biebl@debian.org> - 2016-01-05 01:40 +0100
  Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-04 18:20 +0100
    Re: Prevent shutdown with systemctl <tomas@tuxteam.de> - 2016-01-04 18:50 +0100
      Re: Prevent shutdown with systemctl Stuart Longland <stuartl@longlandclan.id.au> - 2016-01-04 21:20 +0100
        Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-04 21:40 +0100
          Re: Prevent shutdown with systemctl Stuart Longland <stuartl@longlandclan.id.au> - 2016-01-04 22:10 +0100
            Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-04 22:50 +0100
              Re: Prevent shutdown with systemctl Michael Biebl <biebl@debian.org> - 2016-01-05 01:20 +0100
                Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-05 18:20 +0100
      Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-04 21:30 +0100
        Re: Prevent shutdown with systemctl Stuart Longland <stuartl@longlandclan.id.au> - 2016-01-04 22:00 +0100
          Re: Prevent shutdown with systemctl David Wright <deblis@lionunicorn.co.uk> - 2016-01-05 05:50 +0100
        Re: Prevent shutdown with systemctl <tomas@tuxteam.de> - 2016-01-04 22:20 +0100
          Re: Prevent shutdown with systemctl Gary Dale <garydale@torfree.net> - 2016-01-04 22:50 +0100
            Re: Prevent shutdown with systemctl David Wright <deblis@lionunicorn.co.uk> - 2016-01-05 06:10 +0100
            Symlinks vs. hardlinks [was: Prevent shutdown with systemctl] <tomas@tuxteam.de> - 2016-01-05 09:40 +0100
              Re: Symlinks vs. hardlinks "Thomas Schmitt" <scdbackup@gmx.net> - 2016-01-05 11:10 +0100
                Re: Symlinks vs. hardlinks <tomas@tuxteam.de> - 2016-01-05 11:40 +0100
              Re: Symlinks vs. hardlinks [was: Prevent shutdown with systemctl] <tomas@tuxteam.de> - 2016-01-05 16:30 +0100
              Re: Symlinks vs. hardlinks [was: Prevent shutdown with systemctl] David Wright <deblis@lionunicorn.co.uk> - 2016-01-05 16:30 +0100
  Re: Prevent shutdown with systemctl Jude DaShiell <jdashiel@panix.com> - 2016-01-04 19:20 +0100
  Re: Prevent shutdown with systemctl Brian <ad44@cityscape.co.uk> - 2016-01-04 19:30 +0100
    Re: Prevent shutdown with systemctl jdd <jdd@dodin.org> - 2016-01-04 20:10 +0100
      Re: Prevent shutdown with systemctl jdd <jdd@dodin.org> - 2016-01-04 20:30 +0100
      Re: Prevent shutdown with systemctl Chris Bannister <cbannister@slingshot.co.nz> - 2016-01-05 11:10 +0100

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