參考 https://www.cnblogs.com/CloudMan6/p/6875834.html   RUN CMD ENTRYPOINT 這三個Dockerfile指令看上去很類似，很容易混淆。   簡單的說：       RUN 執行命令並建立新的映象層，經常用於安裝軟體     CMD 設定容器啟動後預設執行的命令機器引數，但CMD能夠被 docker run 後面跟的命令列引數替換     ENTRYPOINT 配置容器啟動時執行的命令   shell 和exex 格式   有shell和exec兩種方式可以指定 RUN CMD ENTRYPOINT 要執行的命令，兩者在使用上有細微的區別   shell 格式： <instruction> <command>   例如：   RUN apt-get install -y python3 CMD echo "Hello world" ENTRYPOINT echo "Hello world"   當指令執行時， shell格式底層會呼叫 /bin/sh -c <command>   [email protected]:~/017# cat Dockerfile FROM busybox ENV name www1707 ENTRYPOINT echo "Hello $name" [email protected]:~/017# docker build -t test017 . Sending build context to Docker daemon  2.048kB Step 1/3 : FROM busybox ---> 3a093384ac30 Step 2/3 : ENV name www1707 ---> Running in e43df73f1151 Removing intermediate container e43df73f1151 ---> 973f9b8b29b7 Step 3/3 : ENTRYPOINT echo "Hello $name" ---> Running in 5efc3b5b3053 Removing intermediate container 5efc3b5b3053 ---> c9321b834dbb Successfully built c9321b834dbb Successfully tagged test017:latest

[email protected]:~/017# docker images REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE test017             latest              c9321b834dbb        6 seconds ago       1.2MB myimage             latest              c67728621bdd        33 hours ago        1.2MB busybox             latest              3a093384ac30        7 days ago          1.2MB [email protected]:~/017# docker run test017 Hello www1707   exec格式： <instruction> ["executable","param1","param2",...]   例如：   RUN ["apt-get","install","python3"] CMD ["/bin/echo","Hello world"] ENTRYPOINT ["/bin/echo","Hello world"]   當指令執行時，會直接呼叫command，不會被shell解析   [email protected]:~/017# cat Dockerfile FROM busybox ENV name www1707 ENTRYPOINT ["/bin/echo","Hello,$name"]
[email protected]:~/017# docker build -t test-017 . Sending build context to Docker daemon  2.048kB Step 1/3 : FROM busybox ---> 3a093384ac30 Step 2/3 : ENV name www1707 ---> Running in 6a2a8dcbd2ab Removing intermediate container 6a2a8dcbd2ab ---> 026f3f3c154e Step 3/3 : ENTRYPOINT ["/bin/echo","Hello,$name"] ---> Running in 92c90db5bbc3 Removing intermediate container 92c90db5bbc3 ---> 1f01346313b5 Successfully built 1f01346313b5 Successfully tagged test-017:latest [email protected]:~/017# docker run test-017 Hello,$name     [email protected]:~/017# cat Dockerfile FROM busybox ENV name www1707 ENTRYPOINT ["/bin/sh","-c","echo Hello,$name"]
[email protected]:~/017# docker build -t test-017 . Sending build context to Docker daemon  2.048kB Step 1/3 : FROM busybox ---> 3a093384ac30 Step 2/3 : ENV name www1707 ---> Using cache ---> 026f3f3c154e Step 3/3 : ENTRYPOINT ["/bin/sh","-c","echo Hello,$name"] ---> Running in 459792a5b117 Removing intermediate container 459792a5b117 ---> d163360f72c5 Successfully built d163360f72c5 Successfully tagged test-017:latest [email protected]:~/017# docker run test-017 Hello,www1707     CMD 和 ENTYRPOINT 推薦使用exec格式，因為指令的可讀性更強，更容易理解。   RUN       RUN 使用兩種格式都可以，但是RUN一般用來安裝應用和軟體包，推薦shell格式     RUN apt-get update && apt-get install -y vim wget      先執行update 保證後面安裝的軟體版本是最新的，要不然會可能會安裝一個早期的版本或者直接安裝失敗   CMD       CMD支援三種格式       1、exec格式  CMD ["executable","param1","param2"]         這是CMD推薦的格式     2、CMD ["param1","param2"]          這是為ENTRYPOINT  提供額外引數時的格式，此時 ENTRYPOINT 必須是exec格式     3、CMD command param1 param2         這是shell格式       第二種格式 CMD ["param1","param2"] 要與 exec格式的 ENTRYPOINT 指令配合使用，其使用者是為ENTRYPOINT設定預設引數。       當docker run 後面有引數時，CMD指令將會被忽略   [email protected]:~/017# cat Dockerfile FROM busybox CMD echo "Hello world" [email protected]:~/017# docker build -t test-017 . Sending build context to Docker daemon  2.048kB Step 1/2 : FROM busybox ---> 3a093384ac30 Step 2/2 : CMD echo "Hello world" ---> Running in 15bd85e76424 Removing intermediate container 15bd85e76424 ---> 13e99c60b00d Successfully built 13e99c60b00d Successfully tagged test-017:latest [email protected]:~/017# docker run test-017 Hello world [email protected]:~/017# docker run -it test-017 Hello world [email protected]:~/017# docker run -it test-017 /bin/sh / # / # exit [email protected]:~/017#     ENTRYPOINT       該指令可以讓容器以應用程式或者服務執行。ENTYRPOINT和CMD看上去很像，他們都可以指定要執行的命令及引數。但是ENTYRPOINT不會被忽略，一定會被執行，即使docker run 後面指定了其他命令。       exec格式--推薦格式         ENTYRPOINT ["executable","param1","param2"]   [email protected]:~/017# cat Dockerfile FROM busybox ENTRYPOINT ["/bin/echo","Hello"] CMD ["world"] [email protected]:~/017# docker build -t test-017 . Sending build context to Docker daemon  2.048kB Step 1/3 : FROM busybox ---> 3a093384ac30 Step 2/3 : ENTRYPOINT ["/bin/echo","Hello"] ---> Running in 5fca55e81dd9 Removing intermediate container 5fca55e81dd9 ---> 60978b547d5d Step 3/3 : CMD ["world"] ---> Running in b1f9da2b8ecf Removing intermediate container b1f9da2b8ecf ---> 1957f19e2cb7 Successfully built 1957f19e2cb7 Successfully tagged test-017:latest [email protected]:~/017# docker run test-017 Hello world [email protected]:~/017# docker run -it test-017 www1707 Hello www1707         shell格式--該格式會忽略掉CMD和docker run 後面的引數         ENTRYPOINT command param1 param2   [email protected]:~/017# cat Dockerfile FROM busybox ENTRYPOINT echo hello CMD ["world"] [email protected]:~/017# docker build -t test-017 . Sending build context to Docker daemon  2.048kB Step 1/3 : FROM busybox ---> 3a093384ac30 Step 2/3 : ENTRYPOINT echo hello ---> Running in 683c7c95a0bb Removing intermediate container 683c7c95a0bb ---> 4b76c9e22319 Step 3/3 : CMD ["world"] ---> Running in 3464e96183d6 Removing intermediate container 3464e96183d6 ---> d636aed0e6b4 Successfully built d636aed0e6b4 Successfully tagged test-017:latest [email protected]:~/017# docker run test-017 hello [email protected]:~/017# docker run -it test-017 www1707 hello         最佳實踐   1、RUN 指定用來安裝應用和軟體包 2、ENTRYPOINT用來執行應用或者服務，可以用CMD提供額外的引數，還可以用docker run提供引數或者是替換掉CMD提供的引數 3、CMD可以為容器設定預設的啟動命令，也可以用docker run替換掉