这个 Dockerfile 如何在没有入口点或 cmd 的情况下实际运行 logstash？

Question

只要在这个官方 logstash docker 容器上启动一个容器就可以正确地使 logstash 运行，给定正确的配置。

它没有入口点或 cmd，或任何类似的东西。我也没有在启动命令上发出一个。那么，在这种情况下，logstash 实际上是如何执行的？

我需要知道，因为我出于其他原因需要编辑命令。我们正在运行在 kubernetes 中使用它，但目前只是在本地 docker 上进行测试。

https://github.com/elastic/logstash/blob/7.15/Dockerfile

复制以供参考：

FROM ubuntu:bionic

RUN apt-get update && \
    apt-get install -y zlib1g-dev build-essential vim rake git curl libssl-dev libreadline-dev libyaml-dev  \
      libxml2-dev libxslt-dev openjdk-11-jdk-headless curl iputils-ping netcat && \
    apt-get clean

WORKDIR /root

RUN adduser --disabled-password --gecos "" --home /home/logstash logstash && \
    mkdir -p /usr/local/share/ruby-build && \
    mkdir -p /opt/logstash && \
    mkdir -p /opt/logstash/data && \
    mkdir -p /mnt/host && \
    chown logstash:logstash /opt/logstash

USER logstash
WORKDIR /home/logstash

# used by the purge policy
LABEL retention="keep"

# Setup gradle wrapper. When running any `gradle` command, a `settings.gradle` is expected (and will soon be required).
# This section adds the gradle wrapper, `settings.gradle` and sets the permissions (setting the user to root for `chown`
# and working directory to allow this and then reverts back to the previous working directory and user.
COPY --chown=logstash:logstash gradlew /opt/logstash/gradlew
COPY --chown=logstash:logstash gradle/wrapper /opt/logstash/gradle/wrapper
COPY --chown=logstash:logstash settings.gradle /opt/logstash/settings.gradle
WORKDIR /opt/logstash
RUN for iter in `seq 1 10`; do ./gradlew wrapper --warning-mode all && exit_code=0 && break || exit_code=$? && echo "gradlew error: retry $iter in 10s" && sleep 10; done; exit $exit_code
WORKDIR /home/logstash

ADD versions.yml /opt/logstash/versions.yml
ADD LICENSE.txt /opt/logstash/LICENSE.txt
ADD NOTICE.TXT /opt/logstash/NOTICE.TXT
ADD licenses /opt/logstash/licenses
ADD CONTRIBUTORS /opt/logstash/CONTRIBUTORS
ADD Gemfile.template Gemfile.jruby-2.5.lock.* /opt/logstash/
ADD Rakefile /opt/logstash/Rakefile
ADD build.gradle /opt/logstash/build.gradle
ADD rubyUtils.gradle /opt/logstash/rubyUtils.gradle
ADD rakelib /opt/logstash/rakelib
ADD config /opt/logstash/config
ADD spec /opt/logstash/spec
ADD qa /opt/logstash/qa
ADD lib /opt/logstash/lib
ADD pkg /opt/logstash/pkg
ADD tools /opt/logstash/tools
ADD logstash-core /opt/logstash/logstash-core
ADD logstash-core-plugin-api /opt/logstash/logstash-core-plugin-api
ADD bin /opt/logstash/bin
ADD modules /opt/logstash/modules
ADD x-pack /opt/logstash/x-pack
ADD ci /opt/logstash/ci

USER root
RUN rm -rf build && \
    mkdir -p build && \
    chown -R logstash:logstash /opt/logstash
USER logstash
WORKDIR /opt/logstash

LABEL retention="prune"

Answer 1

如果您查看图像的最后一层 here，它看起来像有一个 ENTRYPOINT ["/usr/local/bin/docker-entrypoint"]。您链接的 Dockerfile 可能不是用于构建映像的文件。

这个 Dockerfile 如何在没有入口点或 cmd 的情况下实际 运行 logstash？

How does this Dockerfile actually run logstash without an entrypoint or cmd?

ubuntu

logstash

docker

kubernetes

这个 Dockerfile 如何在没有入口点或 cmd 的情况下实际运行 logstash？