bug#18214: How to copy modification date with cp?

[Bernhard Voelker]

tags 18214 notabug
close 18214
stop

On 08/07/2014 11:42 AM, Holger Klene wrote:
> I'd like to copy photos from my harddrive to an external USB-drive for my 
> parents. As
> there are many more photos on my harddrive, that I don't want to copy to my 
> parents, I
> created a view folder with symbolic links that point exactly to the folders my 
> parents
> should get.
>
> Now I copy the contents of the view-folder over to the USB-drive with:
> cp -vLRu viewForMyParents usb
>
> After some time, more folders are added and I plan on repeating the copy 
> command to
> update the usb-drive with the latest additions.
>
> The problem is, all files and folders get a timestamp of the moment, when the 
> copy took
> place instead of the original files timestamp.
>
> I reproduced the setup and took a screenshot (cp-error.png). Only that the tar 
> did not
> preserve the symbolic links inside test/myHardDrive/viewForMyParents/
>
> My question is, how can I make cp not updating the timestamps to the moment of 
> the copy
> (e.g. 11:00) but instead let it copy the original files last modified (e.g. 
> 10:something)?
>
> Thanks
> Holger
>
> PS: This is Kubuntu 14.04 with cp (GNU coreutils) 8.21

Thanks for the report, however this is not a bug but rather a question
about how to use cp(1). As your email opened a bug in our bugtracker,
I therefore mark this as not a bug.

Regarding the question, the answer is -p or --preserve=timestamps:

  $ cp --help
  ...
  -p                           same as --preserve=mode,ownership,timestamps
      --preserve[=ATTR_LIST]   preserve the specified attributes (default:
                                 mode,ownership,timestamps), if possible
                                 additional attributes: context, links, xattr,
                                 all

BTW: as you seem to want to repeat the syncing in future again,
I'd personally recommend using rsync(1) rather than cp(1).

Have a nice day,
Berny