This seems like a breaking API change (as you note) for downstream consumers. Seems more correct to create a new image for that.
> On Oct 21, 2016, at 11:50 AM, Daniel J Walsh <dwa...@redhat.com> wrote: > > If we make this change, we would want to do it in Fedora and Centos also. > > https://bugzilla.redhat.com/show_bug.cgi?id=1387282 > > The benefits of making this change are that people new to containers > could follow a simple workflow similar to what the do on the OS, where > all they need to do is install an rpm service and enable and it is ready > to go. > > > # cat Dockerfile > > FROM rhel7 > > RUN dnf -y install httpd; systemctl enabled httpd > > ADD MYAPP / > > > # docker build -t MYAPP . > > > And they are done. Now if they run their container > > docker run -d MYAPP > > And their app runs with systemd/journald and httpd with their app runnin > inside of it. > > > For users who don't want to use systemd, they would just override the > CMD field and their container would work fine. > > Since the current default is bash, they would need to do this anyways. > > > A couple of things will break, > > docker run -ti rhel7 > > Currently runs a shell. With the new change, systemd would start up > inside of the contaienr. > > > Users who want a shell would need to execute > > docker run -ti rhel7 /bin/sh > > (I always do this anyways, but I guess some people do not) > > > The other big issue is on stopping of containers. docker stop currently > defaults to sending SIGTERM to the pid 1 of the container. > > systemd requires that SIGRTMIN+3 be sent to it to close down properly. > If we want to have systemd work by default, we would > > need to change the default SIGSTOP of the base image. This means any > application based on the base image that does not > > override the SIGSTOP would get SIGRTMIN+3. Most apps will die when they > get this signal, but if the App had a signal handler for > > SIGTERM, the signal handler will not work correctly. > > > Adding > > SIGSTOP SIGTERM > > to a Dockerfile would fix the issue, but it will cause unexpected > breakage. I don't see an easy solution for this. > > >
