[Unison-hackers] Sneaker Net or Incremental Backup

[Duane McKinney]

Or from Version 2.31.4
copyprog xxx
     A string giving the name of an external program that can be used to 
copy large files efficiently (plus command-line switches telling it to 
copy files in-place). The default setting invokes rsync with appropriate 
options—most users should not need to change it.

copyprogrest xxx
     A variant of copyprog that names an external program that should be 
used to continue the transfer of a large file that has already been 
partially transferred. Typically, copyprogrest will just be copyprog 
with one extra option (e.g., –partial, for rsync). The default setting 
invokes rsync with appropriate options—most users should not need to 
change it.

copythreshold n
     A number indicating above what filesize (in kilobytes) Unison 
should use the external copying utility specified by copyprog. 
Specifying 0 will cause all copies to use the external program; a 
negative number will prevent any files from using it. The default is -1. 
See the Making Unison Faster on Large Files section for more information.

I guess I should have checked out the Beta Documentation 1st.  I'll try 
messing around with using a shell script as the copyprog.  I would 
assume that it would work just fine.  My plan is to write a shell script 
which ignores the destination unison tells it, and instead copies it to 
a usb drive.

I'll probably report back on this in a week or so.  Currently I am 
running 2.27, so I have some compiling and testing to do.

Duane McKinney wrote:
> What about a flag that tells it to instead of executing the copies, just 
> prints out a list of the files that would be copied?  A proper name is 
> escaping me at the moment, but it is a common option on programs.
> 
> Benjamin Pierce wrote:
>> Both of these features would be easy to implement using information  
>> that Unison already has available.  If you want to give it a try, I  
>> can tell you where to start.  (I'd be reluctant, though, to add this  
>> code to the main sources -- Unison arguably has too many flags and  
>> switches already!)
>>
>> Best,
>>
>>      - Benjamin
>>
>> On Dec 27, 2008, at 10:27 AM, Duane McKinney wrote:
>>
>>> I searched, but came up empty.  Can this be done.
>>> I sync two offices using unison.
>>> 1) (Optional)I would like to be able to set a preference that says,  
>>> don't try to
>>> sync a file if it would require X bytes transferred
>>> 2) Get a list of changed files from a root.  That way I can copy the  
>>> files to a
>>> removable drive and sync them when I get to the other office.
>>>
>>> Here is my reasoning.  Most of the time, root changes are very  
>>> small, a few MB.
>>> But Let's say that I download a new CENTOS release and place it on  
>>> the file
>>> server.  This may be a poor example, because I could retrieve it  
>>> over the
>>> internet again, but just bear with me.  I would like for unison, to  
>>> instead of
>>> trying to sync this file over the network to skip it.  The I would  
>>> like to be
>>> able to say once a week, run a job, that would take the differences  
>>> in the root
>>> and sent them to a USB drive.  I can then carry this drive to  
>>> location 2, and
>>> update the root there.   Then from my understanding, the network  
>>> sync would
>>> detect that both roots are identical.
>>>
>>> That way, our bandwidth isn't being eaten up for hours/days, trying  
>>> to perform a
>>> sync that will most likely fail because it will take so long.
>>>
>>> Also, this would be more useful, than synchronizing the whole root  
>>> to a usb
>>> drive, because, the total of the data that I am synchronizing is >  
>>> 1TB.  I would
>>> not mind moving a few GB (<100) via USB.  I am trying to avoid  
>>> needing either, a
>>> lot of time, or a bunch of USB drives (one for each root).
>>>
>>> I have not yet looked at the source, but I would assume that most of  
>>> the items
>>> required for this feature are already in place.  Is it feasible?  Is  
>>> there
>>> already a way?
>>>
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