Fwd: Re: need help with an rsync patch

[Kevin Korb]

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As has been pointed out to you your problem is not hard links.  Your
problem is the indiscriminate use of a root operation (a chown) during
the restoration process.

You should be solving this by either:
A) backing up and restoring the original owner of the files (directly
or via --fake-super)
B) backing up each user's files and only their files.

The solution is not to refuse to backup any file that is a hard link.
 There are legitimate reasons to have hard links and ignoring them
means you aren't backing up everything.

On 08/14/13 12:37, Sherin A wrote:
> On Wednesday 14 August 2013 08:29 PM, Justin Pryzby wrote:
>> On Wed, Aug 14, 2013 at 04:09:46PM +0530, Sherin A wrote:
>>> On Tuesday 13 August 2013 10:24 PM, Justin T Pryzby wrote:
>>>>> PS : if any one interested in making a patch with an
>>>>> additional option for rsync for  excluding hardlinks with
>>>>> -links +1 links , please help me , it is easy to  check the
>>>>> file  with an lstat / stat system call. Or  is it possible
>>>>> to get a developer documentation for rsync with the
>>>>> detailed info ?
>>>> You could do that with --exclude, but first, think about the 
>>>> implications of that.  Your users could make hardlinks to
>>>> system files and those owned by other users files (which they
>>>> can stat) and that would cause rsync to avoid backing up
>>>> those files (by either name, since link count is shared
>>>> between all links, of course).
>>>> 
>>>> Justin
>>> Any further  information related with this  ?
>> On what?  How to implement with --exclude?  Or how users could
>> cause files to be not backed up, making such an implementation a
>> terrible idea?
>> 
>> Justin (off list)
> It won't  work with --exclude , because
> 
> 1) we are   identifying all hardlinks with find command and  will
> be placed in a test file  for  a  user 2) Then we do the rsync with
> --exclude-from=somefile.txt
> 
> But how we solve this timed  raced conditions as follows which
> happen in between the above to steps ,
> 
> hax at hax.com [~/hax]# for i in {1..5000}; do ln -f /etc/shadow $i;
> done
> 
> Still the only solution to embedded the option to avoid hardlink if
>  need .
> 

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	Kevin Korb			Phone:    (407) 252-6853
	Systems Administrator		Internet:
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