Bug 1307049

Description of problem:
Building a base container from scratch with a tar archive fails if the archive contains file capabilities.

Version-Release number of selected component (if applicable):
docker-1.8.2-10

How reproducible:
Always

Steps to Reproduce:
1. Create a base disk image with livemedia-creator

example commands used are available on github: 
https://github.com/CentOS/sig-cloud-instance-build/tree/livemedia_builds/docker

2. Create a container from the resulting tarball via a very basic Dockerfile. Something like the following:

=====
FROM scratch
MAINTAINER me
ADD centos-img.tar.xz /
=====

docker run --rm -t centostest .

3. run the container and observe that the capabilities are stripped from the iputils package. 

[root@73ba9b203c2b /]# rpm -V iputils
........P    /usr/bin/ping
........P    /usr/bin/ping6
........P    /usr/sbin/arping
........P    /usr/sbin/clockdiff


4. Create the archive with tar directly:

kpartx -a /var/tmp/centos-7-root
mount /dev/mapper/loop0p1 /mnt

tar -C /mnt/ -jcf centos-img.tar.bz2 .

Build docker container using this tarball, just as above. 

Same output from running rpm -V iputils in this container.

[root@92bca8435dd8 /]# rpm -V iputils
........P    /usr/bin/ping
........P    /usr/bin/ping6
........P    /usr/sbin/arping
........P    /usr/sbin/clockdiff


5. Create archive with --xattr, to maintain file capabilities

tar --xattrs -C /mnt/ -jcf centos-img.tar.bz2 .

Build docker container using this tarball:


Note that the resulting container is only slightly larger than the tarball itself. 

6. Examine the contents of the docker container:

docker create --name wtf c7build

[root@lappy ~]# docker export wtf | tar -t
.dockerenv
.dockerinit
centos-img.tar.bz2
dev/
dev/console
dev/pts/
dev/shm/
etc/
etc/hostname
etc/hosts
etc/mtab
etc/resolv.conf
lib64
proc/
sys/


Docker's for some reason not extracted this archive, but instead stuffed it inside the container which won't work. 

Validate that the capabilities are intact by importing the tar archive directly

cat centos-img.tar.bz2 | docker import - capvalidate

docker run --rm -it capvalidate /bin/bash
[root@cf2021d70a42 /]# rpm -V iputils
[root@cf2021d70a42 /]#



Actual results:
containers including files with capabilities (like ping) don't get unpacked via an ADD in a dockerfile

Expected results:
ADD unpacks the tarball and a base container is happily created.