【Docker】Dockerfile 之 ENTRYPOINT（三）
參考教程：https://docs.docker.com/engine/reference/builder/
環境
- virtual box 6.1
- centos 7.8
- docker 19.03
ENTRYPOINT 的 shell 格式示例
You can specify a plain string for the ENTRYPOINT and it will execute in /bin/sh -c. This form will use shell processing to substitute shell environment variables, and will ignore any CMD
docker run command line arguments. To ensure that docker stop will signal any long running ENTRYPOINT executable correctly, you need to remember to start it with exec:您可以為
ENTRYPOINT 指定一個純字串，它將在 /bin/sh -c 中執行。這種形式將使用外殼處理環境變數，並且將忽略任何 CMD 或 docker run 命令列引數。為了確保 docker stop 能夠正確通知任何長期執行的 ENTRYPOINTexec 啟動它：
FROM ubuntu
ENTRYPOINT exec top -b
When you run this image, you’ll see the single PID 1 process:
當執行這個映象時，您會看到一個 PID 1 程序：
$ docker run -it --rm --name test top Mem: 1704520K used, 352148K free, 0K shrd, 0K buff, 140368121167873K cached CPU: 5% usr 0% sys 0% nic 94% idle 0% io 0% irq 0% sirq Load average: 0.08 0.03 0.05 2/98 6 PID PPID USER STAT VSZ %VSZ %CPU COMMAND 1 0 root R 3164 0% 0% top -b
Which exits cleanly on docker stop:
使用 docker stop 可以完全退出：
$ /usr/bin/time docker stop test
test
real 0m 0.20s
user 0m 0.02s
sys 0m 0.04s
If you forget to add exec to the beginning of your ENTRYPOINT:
如果您忘記在 ENTRYPOINT 的開頭新增 exec：
FROM ubuntu
ENTRYPOINT top -b
CMD --ignored-param1
You can then run it (giving it a name for the next step):
然後可以執行它（為下一步命名）：
$ docker run -it --name test top --ignored-param2
Mem: 1704184K used, 352484K free, 0K shrd, 0K buff, 140621524238337K cached
CPU: 9% usr 2% sys 0% nic 88% idle 0% io 0% irq 0% sirq
Load average: 0.01 0.02 0.05 2/101 7
PID PPID USER STAT VSZ %VSZ %CPU COMMAND
1 0 root S 3168 0% 0% /bin/sh -c top -b cmd cmd2
7 1 root R 3164 0% 0% top -b
You can see from the output of top that the specified ENTRYPOINT is not PID 1.
從 top 的輸出中可以看到，指定的 ENTRYPOINT 不是 PID 1。
If you then run docker stop test, the container will not exit cleanly - the stop command will be forced to send a SIGKILL after the timeout:
如果隨後執行 docker stop test，則容器將不會乾淨退出。超時後，將強制執行 stop 命令傳送 SIGKILL：
$ docker exec -it test ps aux
PID USER COMMAND
1 root /bin/sh -c top -b cmd cmd2
7 root top -b
8 root ps aux
$ /usr/bin/time docker stop test
test
real 0m 10.19s
user 0m 0.04s
sys 0m 0.03s
總結
介紹了 Dockerfile 中 ENTRYPOINT 指令的 shell 格式的使用。