入口点脚本中的 Docker exec 命令失败

Question

Following the suggestion on Execute a script before CMD (I needed to clear out a temp dir before a container is re-launched, to fix a bug), I modified my docker file from using a CMD, to entrypoint as follows:

ENTRYPOINT ["/app/entrypoint.sh", "/usr/bin/java -Dlog4j.configurationFile=/app/resources/LINUX/${LOG4J_FILE} -Dpa.config=/app/resources/LINUX/${CONFIG_FILE} -jar /app/app.jar"]

and in entrypoint file end after the rm -rf command:

exec "$@"

But docker is unable to launch the container, it exits, container log shows:

+ exec '/usr/bin/java -Dlog4j.configurationFile=/app/resources/LINUX/${LOG4J_FILE} -Dpa.config=/app/resources/LINUX/${CONFIG_FILE} -jar /app/app.jar' /app/entrypoint.sh: line 7: /usr/bin/java -Dlog4j.configurationFile=/app/resources/LINUX/${LOG4J_FILE} -Dpa.config=/app/resources/LINUX/${CONFIG_FILE} -jar /app/app.jar: No such file or directory - what does this mean? what is wrong?

Answer 1

You need to break the JSON-array-format command line into separate words. Since you've explicitly told Docker that the “command” part of this is a single word, it's looking for a binary file in /usr/bin named java -Dlog4j.configurationFile=... , with the spaces and options and all as part of the filename, and not finding it.

You typically don't want to embed the command you want to run in ENTRYPOINT , especially if you're using this wrapper layout. Make ENTRYPOINT just be the name of the script ending in exec "$@" ; it must use JSON-array syntax. Make CMD be the actual command you want to run, in whichever syntax is more convenient. (If you're trying to expand environment variables, the shell-oriented syntax might be better.)

ENTRYPOINT ["/app/entrypoint.sh"]
CMD /usr/bin/java \
  -Dlog4j.configurationFile=/app/resources/LINUX/${LOG4J_FILE} \
  -Dpa.config=/app/resources/LINUX/${CONFIG_FILE} \
  -jar /app/app.jar

I've found this pattern to be sufficiently common and useful that I'd generally recommend using ENTRYPOINT only for this sort of wrapper script; prefer putting the command to start your application as CMD , even if you don't have an entrypoint wrapper.