Re: [Qemu-devel] [PATCH v2 0/3] Support building qemu-user powered docker test images

[Riku Voipio]

On 13 June 2016 at 12:22, Alex Bennée <address@hidden> wrote:
>
> Fam Zheng <address@hidden> writes:
>
>> On Wed, 06/08 17:35, Alex Bennée wrote:
>>> Hi,
>>>
>>> This is a re-spin of the previous series built on top of
>>> fam/docker.next. I've made the changes suggested in the last review
>>> and split the first patch apart to separate (and fix) the build
>>> directory changes first.
>>>
>>> Now it no longer messes with the docker file you can actually
>>> cross-build tests. First ensure you build the debian-bootstrap image:
>>>
>>>     DEB_ARCH=armhf DEB_TYPE=testing \
>>>       ./tests/docker/docker.py build qemu:debian-bootstrap \
>>>       ./tests/docker/dockerfiles/debian-bootstrap.docker \
>>>       --include-executable=./arm-linux-user/qemu-arm
>>
>> This can take long depending on the network - I had to explicitly use a close
>> mirror in the pre script to test this, not sure why the mirror redirector
>> doesn't work. Eventually I get this error once the pre script succeeds and
>> docker build starts:
>>
>> Sending build context to Docker daemon 235.1 MB
>> Step 1 : FROM scratch
>>  --->
>> Step 2 : ADD . /
>>  ---> 807bfa810b0c
>> Removing intermediate container e57ded00b227
>> Step 3 : RUN sed -i 's/in_target mount/echo not for docker in_target 
>> mount/g' /debootstrap/functions
>>  ---> Running in fd80232b38fc
>> rpc error: code = 2 desc = "oci runtime error: exec format error"
>>
>> IIUC the sed is an armhf binary? Is something missing in the docker file? I
>> cannot find where the copied qemu-arm is used...
>
> Ahh I realise I missed out the implicit binfmt_misc needs to be set up.
> So on my Ubuntu system just having qemu-user installed means the host
> system binfmt_misc is set up for armhf binaries to run
> /usr/bin/qemu-arm. I haven't experimented with explicitly setting up
> binfmt_misc in the container because it was already working :-/

The containment leaks here. If your host has registered binfmt_misc,
identical settings will be visible in container. You can't change the
settings inside docker, unless you start with --privileged. And
changing binfmt_misc settings inside docker will also change the
settings in the host. So one needs to tiptoe around setting it up...

>>
>> Fam
>>
>>>
>>> And then run the test quick target:
>>>
>>>     make address@hidden J=9 V=1
>>>
>>> I'll leave it up to you how we cleanly integrate multi-arch builds
>>> into the Make system ;-)
>>>
>>> Alex Bennée (3):
>>>   tests/docker/docker.py: docker_dir outside build
>>>   tests/docker/docker.py: support --include-executable
>>>   add debian-bootstrap.docker target (and pre script)
>>>
>>>  tests/docker/docker.py                           | 68 
>>> +++++++++++++++++++++---
>>>  tests/docker/dockerfiles/debian-bootstrap.docker | 21 ++++++++
>>>  tests/docker/dockerfiles/debian-bootstrap.pre    |  5 ++
>>>  3 files changed, 86 insertions(+), 8 deletions(-)
>>>  create mode 100644 tests/docker/dockerfiles/debian-bootstrap.docker
>>>  create mode 100755 tests/docker/dockerfiles/debian-bootstrap.pre
>>>
>>> --
>>> 2.7.4
>>>
>
>
> --
> Alex Bennée