Re: [Qemu-devel] [PATCH RFC v4 3/4] docker: Support "QEMU_CHROOT" in dockerfiles

["Alex Bennée" <alex.bennee@linaro.org>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 11/07/2016 05:20, Fam Zheng wrote:
>> This allows a docker file to say "ENV QEMU_CHROOT /path/to/new/root" to
>> indicate that the test execution should be done in a chroot in the
>> container.
>>
>> Bind mount dev,sys,proc into QEMU_CHROOT to make them avaiable for
>> testing scripts.
>>
>> The SYS_ADMIN is a required capability for mount, add it to the
>> docker run command line.
>>
>> Signed-off-by: Fam Zheng <famz@redhat.com>
>> ---
>>  tests/docker/Makefile.include |  1 +
>>  tests/docker/run              | 12 ++++++++++++
>>  2 files changed, 13 insertions(+)
>>
>> diff --git a/tests/docker/Makefile.include b/tests/docker/Makefile.include
>> index c5546ee..e9821ba 100644
>> --- a/tests/docker/Makefile.include
>> +++ b/tests/docker/Makefile.include
>> @@ -107,6 +107,7 @@ docker-run-%: docker-qemu-src
>>  		$(call quiet-command,\
>>  			$(SRC_PATH)/tests/docker/docker.py run $(if $V,,--rm) \
>>  				-t \
>> +				--cap-add SYS_ADMIN \
>>  				$(if $(DEBUG),-i,--net=none) \
>>  				-e TARGET_LIST=$(TARGET_LIST) \
>>  				-e EXTRA_CONFIGURE_OPTS=$(EXTRA_CONFIGURE_OPTS) \
>> diff --git a/tests/docker/run b/tests/docker/run
>> index 38ce789..4e80cc3 100755
>> --- a/tests/docker/run
>> +++ b/tests/docker/run
>> @@ -19,6 +19,18 @@ fi
>>
>>  BASE="$(dirname $(realpath $0))"
>>
>> +# cp files into the chroot and execute there
>> +if test -n "$QEMU_CHROOT"; then
>> +    mkdir -p $QEMU_CHROOT/$BASE
>> +    cp $BASE/* $QEMU_CHROOT/$BASE
>> +    QEMU_CHROOT_SAVE="$QEMU_CHROOT"
>> +    for bp in dev sys proc; do
>> +        mount --bind /$bp $QEMU_CHROOT/$bp
>
> Can you ask docker to do these bind mounts instead?

AFAICT docker's various mount directives are all focused on tasks like mounting data
volumes from the host into the container.

It's a bit of a shame having to do this as the original approach was to
use docker to avoid having fancy bind mounts on my hosts system. We are
now getting to inception levels of nesting here. But the benefit is not
requiring the host having the pre-requisites to bootstrap the system.

That said looking at the debootstrap requirements I've seen instructions
that start with download the deb, ar extract and then run the script by
hand so maybe this is over complicating things?

Is it possible to bootstrap a Fedora rootfs with a similar script?

>
> Thanks,
>
> Paolo
>
>> +    done
>> +    QEMU_CHROOT="" chroot $QEMU_CHROOT_SAVE $BASE/run "$@"
>> +    exit 0
>> +fi
>> +
>>  # Prepare the environment
>>  . /etc/profile || true
>>  export PATH=/usr/lib/ccache:$PATH
>>


--
Alex Bennée