Add Support for use CMD to start container

[swift1911]

I use supervise like s6-overlay to handle PID 1 for container, jib plugin use entrypoint to start container and overwrite my baseimage entrypoint, so i want to use CMD to start jib generated container

like this:

<container>
            <jvmFlags>
                  <jvmFlag>-javaagent:/data0/java/deploy/pinpoint.agent/pinpoint-bootstrap.jar</jvmFlag>
                  <jvmFlag>-Dpinpoint.agentId=docker</jvmFlag>
                  <jvmFlag>-Dpinpoint.applicationName=docker-test</jvmFlag>
            </jvmFlags>
      <mainClass>com.fangdd.bwfs.server.container.Application</mainClass>
      <exec>CMD</exec>
</container>

[chanseokoh]

Hi @swift1911,

Let me check if I understood you correctly: you don't want Jib to overwrite the entrypoint and CMD, and you want Jib to just inherit and use the entrypoint and CMD that whatever base image has, right?

[swift1911]

@chanseokoh Yes, this is the meaning

[chanseokoh]

Now the question is, where/how to indicate Jib to not overwrite the entrypoint and CMD, e.g., a new configuration parameter or a system property?

[swift1911]

@chanseokoh i think that a a new configuration parameter is better

[coollog]

Hi @swift1911 , what is the specific entrypoint (full container entrypoint) that you would like to run your container with? We are trying to understand your use case.

[swift1911]

@coollog this is my Dockerile, i want to use s6-overlay to init and handle pid 1,if jib use entrypoint to run java application, it will override my init

FROM alpine
RUN apk add busybox-extras bash vim lsof strace pstree git curl tzdata
ADD https:/just-containers/s6-overlay/releases/download/v1.21.4.0/s6-overlay-amd64.tar.gz /tmp/
RUN gunzip -c /tmp/s6-overlay-amd64.tar.gz | tar -xf - -C /
ENV TZ Asia/Shanghai
ENTRYPOINT ["/init"]

[loosebazooka]

@swift1911 so you're expected execution is something like?

/init java -cp <some-classpath> <some-main-class> ...

[swift1911]

@loosebazooka yes

[coollog]

Hi @swift1911, have you tried using the <entrypoint> configuration?

<container>
  <entrypoint>/init</entrypoint>
</container>

[swift1911]

@coollog in some condition, /init command might be replace by other, hard code /init in jib may cause tech debt

[chanseokoh]

The feature to inherit ENTRYPOINT and CMD will be available in the next release.

Gradle: jib.container.entrypoint = 'INHERIT'
Maven: <container><entrypoint>INHERIT</entrypoint></container>