如何在码头集装箱内使用cron

Question

我试着在码头图片“jenkinsci/蓝海洋”中添加crontab，但是在它之后，jenkins没有启动。问题在哪里？事先非常感谢您的帮助。

<Dockerfile>

FROM jenkinsci/blueocean:1.17.0
USER root
ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.1.9/supercronic-linux-amd64 \
    SUPERCRONIC=supercronic-linux-amd64 \
    SUPERCRONIC_SHA1SUM=5ddf8ea26b56d4a7ff6faecdd8966610d5cb9d85
 RUN curl -fsSLO "$SUPERCRONIC_URL" \
 && echo "${SUPERCRONIC_SHA1SUM}  ${SUPERCRONIC}" | sha1sum -c - \
 && chmod +x "$SUPERCRONIC" \
 && mv "$SUPERCRONIC" "/usr/local/bin/${SUPERCRONIC}" \
 && ln -s "/usr/local/bin/${SUPERCRONIC}" /usr/local/bin/supercronic

ADD crontab /etc/crontab
CMD ["supercronic", "/etc/crontab"]

<crontab>
# Run every minute
*/1 * * * * echo "hello world"


commands:
$docker build -t jenkins_test .
$docker run -it -p 8080:8080 --name=container_jenkins jenkins_test

Answer 1

如果使用docker inspect jenkinsci/blueocean:1.17.0，它的切入点是：

"Entrypoint": [
    "/sbin/tini",
    "--",
    "/usr/local/bin/jenkins.sh"
],

因此，当启动容器时，它将首先执行下一个脚本。

/usr/local/bin/jenkins.sh:

#! /bin/bash -e

: "${JENKINS_WAR:="/usr/share/jenkins/jenkins.war"}"
: "${JENKINS_HOME:="/var/jenkins_home"}"
touch "${COPY_REFERENCE_FILE_LOG}" || { echo "Can not write to ${COPY_REFERENCE_FILE_LOG}. Wrong volume permissions?"; exit 1; }
echo "--- Copying files at $(date)" >> "$COPY_REFERENCE_FILE_LOG"
find /usr/share/jenkins/ref/ \( -type f -o -type l \) -exec bash -c '. /usr/local/bin/jenkins-support; for arg; do copy_reference_file "$arg"; done' _ {} +

# if `docker run` first argument start with `--` the user is passing jenkins launcher arguments
if [[ $# -lt 1 ]] || [[ "$1" == "--"* ]]; then

  # read JAVA_OPTS and JENKINS_OPTS into arrays to avoid need for eval (and associated vulnerabilities)
  java_opts_array=()
  while IFS= read -r -d '' item; do
java_opts_array+=( "$item" )
  done < <([[ $JAVA_OPTS ]] && xargs printf '%s\0' <<<"$JAVA_OPTS")

  readonly agent_port_property='jenkins.model.Jenkins.slaveAgentPort'
  if [ -n "${JENKINS_SLAVE_AGENT_PORT:-}" ] && [[ "${JAVA_OPTS:-}" != *"${agent_port_property}"* ]]; then
java_opts_array+=( "-D${agent_port_property}=${JENKINS_SLAVE_AGENT_PORT}" )
  fi

  if [[ "$DEBUG" ]] ; then
java_opts_array+=( \
  '-Xdebug' \
  '-Xrunjdwp:server=y,transport=dt_socket,address=5005,suspend=y' \
)
  fi

  jenkins_opts_array=( )
  while IFS= read -r -d '' item; do
jenkins_opts_array+=( "$item" )
  done < <([[ $JENKINS_OPTS ]] && xargs printf '%s\0' <<<"$JENKINS_OPTS")

  exec java -Duser.home="$JENKINS_HOME" "${java_opts_array[@]}" -jar ${JENKINS_WAR} "${jenkins_opts_array[@]}" "$@"
fi

# As argument is not jenkins, assume user want to run his own process, for example a `bash` shell to explore this image
exec "$@"

从上面的脚本中可以看到，如果将CMD ["supercronic", "/etc/crontab"]添加到您自己的dockerfile中，那么当容器启动时，它等于执行next：

/usr/local/bin/jenkins.sh "supercronic" "/etc/crontab"

由于if [[ $# -lt 1 ]] || [[ "$1" == "--"* ]]; then不匹配，它将直接在最后一行执行exec "$@，这将导致jenkins start code永不执行。

要修复它，您必须使用自己的docker-entrypoint.sh来覆盖它的默认入口点：

docker-entrypoint.sh:

#!/bin/bash

supercronic /etc/crontab &
/usr/local/bin/jenkins.sh

文档：

FROM jenkinsci/blueocean:1.17.0
USER root
ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.1.9/supercronic-linux-amd64 \
    SUPERCRONIC=supercronic-linux-amd64 \
    SUPERCRONIC_SHA1SUM=5ddf8ea26b56d4a7ff6faecdd8966610d5cb9d85
RUN curl -fsSLO "$SUPERCRONIC_URL" \
 && echo "${SUPERCRONIC_SHA1SUM}  ${SUPERCRONIC}" | sha1sum -c - \
 && chmod +x "$SUPERCRONIC" \
 && mv "$SUPERCRONIC" "/usr/local/bin/${SUPERCRONIC}" \
 && ln -s "/usr/local/bin/${SUPERCRONIC}" /usr/local/bin/supercronic

ADD crontab /etc/crontab
COPY docker-entrypoint.sh /
RUN chmod +x /docker-entrypoint.sh
ENTRYPOINT ["/sbin/tini", "--", "/docker-entrypoint.sh"]