Building in a privileged mode

Expected Behavior

docker-slim build supports --privileged mode, like docker run.

Actual Behavior

docker slim build runs a container in a non-privileged mode which means systemctl and systemd services don't work, e.g.:

❯ docker-slim build --target myimage --http-probe=false --exec "sudo systemctl status"
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cmd=build info=exec message='changing continue-after from probe to nothing because http-probe is disabled'
cmd=build info=exec message='updating continue-after mode to exec'
cmd=build state=started
cmd=build info=params target='myimage' continue.mode='exec' rt.as.user='true' keep.perms='true' tags=''
cmd=build state=image.inspection.start
cmd=build info=image id='sha256:4d0dea302c83b62d0421f240110d5d63b820483c9bdac71fb16a0379cab41022' size.bytes='11744295317' size.human='12 GB'
cmd=build info=image.stack index='0' name='myimage:0.2.0' id='sha256:4d0dea302c83b62d0421f240110d5d63b820483c9bdac71fb16a0379cab41022'
cmd=build state=image.inspection.done
cmd=build state=container.inspection.start
cmd=build info=container id='b5a51e04160cf9c865959be1d84c9c8cbe2edbad93d4bc7975245d2c73a8f330' status='created' name='dockerslimk_18146_20210708131249'
cmd=build info=cmd.startmonitor status='sent'
cmd=build info=event.startmonitor.done status='received'
cmd=build info=container name='dockerslimk_18146_20210708131249' id='b5a51e04160cf9c865959be1d84c9c8cbe2edbad93d4bc7975245d2c73a8f330' target.port.list='55041,55038,55039,55040' target.port.info='80/tcp => 0.0.0.0:55041,8080/tcp => 0.0.0.0:55038,4224/tcp => 0.0.0.0:55039,443/tcp => 0.0.0.0:55040' message='YOU CAN USE THESE PORTS TO INTERACT WITH THE CONTAINER'
cmd=build info=continue.after mode='exec' message='provide the expected input to allow the container inspector to continue its execution'
cmd=build info=continue.after mode='exec' shell='sudo systemctl status'
docker-slim[build][exec]: output: Failed to get D-Bus connection: Operation not permitted
cmd=build info=continue.after mode='exec' exitcode='1'
cmd=build state=container.inspection.finishing
cmd=build info=continue.after mode='exec' message='fatal: exec cmd failure'
cmd=build state=exited code=1
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Any systemctl commands returns this error:

docker-slim[build][exec]: output: Failed to get D-Bus connection: Operation not permitted

Steps to Reproduce the Problem

1. Pull the centos:8 image
2. Run docker-slim build --target centos --exec "systemctl status"

Specifications

• Version: docker-slim version darwin|Transformer|1.36.1|d8f2be23d44bf9f96c5f1f7e970c739106d17996|2021-06-21_03:24:08AM
• Platform: macOS

Start by reproducing the docker-slim build command with the centos:8 image and systemctl status, then trace the build command's container-creation path and its runtime options. Compare that behavior with Docker's --privileged mode. Done means privileged builds can run systemctl without the reported D-Bus permission error.