Can I extract an overwriting tar archive, while retaining the ownership of the original destination file(s)?

Question

I have a particular use case, where I want to extract a tar archive (as root) and intentionally overwrite some destination file(s) with the contents of the archive. This is all fine and easily achievable, but I also want to retain the original ownership and permissions of the original destination file(s). As an example:

$ touch file && tar cf test.tar.gz file && sudo chown www-data:www-data file && sudo tar xf test.tar.gz && ls -l file -rw-r--r-- 1 tim tim 0 May 1 11:26 file

Here I create a file as my user (tim:tim), archive it, change its ownership to www-data:www-data, then (as root) extract the archive, overwriting the original file. As you can see, its ownership has been modified to that of the file in its pre-archived state, whereas post extraction, I want it to be owned by www-data:www-data.

I've had a fairly close look at the tar man page, but can't see an immediately obvious way to do what I want. Am I missing anything?

Answer 1

As a normal user, you wouldn't be able to overwrite the file owned by www-data with only write permissions for the owner, so what you want couldn't work in your example.

What would work, if your user is permitted to write to these files, is to use --overwrite. However you will get errors when tar tries to change the modification time and permissions of the file, because again you as a regular user aren't permitted to do that to files that don't belong to you.