Docker Dockerfile ENTRYPOINT

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Dockerfile ENTRYPOINT有两种形式

  • exec
  • shell
exec(preferred) shell
ENTRYPOINT [“executable”, “param1”, “param2”] command param1 param2
Command line arguments to docker run appended not being used
ENTRYPOINT will be started as a subcommand of /bin/sh -c
default N/A /bin/sh -c (start it with exec to sned stop signal)
CMD [“exec_cmd”, “p1_cmd”] exec_entry p1_entry exec_cmd p1_cmd /bin/sh -c exec_entry p1_entry

ENTRYPOINT exec

FROM alpine:3.8
ENTRYPOINT ["top", "-b"]

因为没有sh进程，所以命令行没有环境变量替换。

可以增加sh

FROM alpine:3.8
ENTRYPOINT ["/bin/sh", "-c"]
CMD ["exec top -b -u $UID"]

ENTRYPOINT shell

CMD无效

FROM alpine:3.8
ENTRYPOINT exec top -b

ENTRYPOINT作为sh的子命令执行即

实际执行/bin/sh -c "exec top -b"

验证

docker build -t cmd .
docker run -it --rm cmd cmd1 cmd2 cmd3


Mem: 4750556K used, 4318692K free, 555320K shrd, 176952K buff, 1907592K cached
CPU:   0% usr   0% sys   0% nic  99% idle   0% io   0% irq   0% sirq
Load average: 0.40 0.28 0.22 4/973 5
  PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND
    1     0 root     R     1524   0%   1   0% top -b

ENTRYPOINT ["sh", "-c"]
CMD ["exec java -jar $APP_FILE"]

类似执行如下指令

/bin/sh -c "exec java -jar $APP_FILE"
DOCKER

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