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目錄

• 先上結(jié)論（適用所有鏡像）
• Docker RUN 覆蓋容器主進(jìn)程命令
• CMD
• docker-compose中的覆蓋主進(jìn)程命令
• Entrypoint命令
• 分析結(jié)論
• 補(bǔ)充

容器啟動(dòng)直接退出，想進(jìn)入容器調(diào)試改怎么辦

使用過docker的朋友大概率會(huì)遇到docker啟動(dòng)容器失敗或執(zhí)行完直接退出的情況，如果我想進(jìn)入容器手動(dòng)執(zhí)行命令調(diào)試，該怎么辦吶？

docker容器啟動(dòng)失敗正常都是由于啟動(dòng)主進(jìn)程退出導(dǎo)致的，主進(jìn)程啟動(dòng)命令往往都是由鏡像Dockerfile文件最后的ENTRYPOINT或CMD定義的，此時(shí)可覆蓋主進(jìn)程啟動(dòng)命令，更換一個(gè)掛起的命令即可。我常用掛起命令：/bin/bash

所以，我們要解決的核心問題就是：如何使用掛起命令覆蓋ENTRYPOINT或CMD定義的容器主進(jìn)程命令？

先上結(jié)論（適用所有鏡像）

1. docker run -it –entrypoint /bin/bash鏡像，執(zhí)行后直接進(jìn)入容器。

2. 若docker-compose啟動(dòng)容器，則需要修改docker-compose.yml文件，在對(duì)應(yīng)服務(wù)下增加如下高亮顯示信息；然后docker-compose重新up

version: '3'
services:
  cmd:
    image: 鏡像
    container_name: 容器名
    entrypoint:
    - tail
    - -f
    - /dev/null

執(zhí)行命令進(jìn)入容器 docker exec -it 容器名 /bin/bash

以下為詳細(xì)分析過程：

查看鏡像的dockerfile文件（docker history –no-trunc image），檢查最后容器啟動(dòng)主進(jìn)程的命令是什么樣的，ENTRYPOINT？CMD？還是它們的組合？覆蓋方式稍有不同。為方便演示，我構(gòu)造了一個(gè)簡單Dockerfile文件做案例。

Docker RUN 覆蓋容器主進(jìn)程命令

docker run 使用-it交互參數(shù)，覆蓋命令/bin/bash

CMD

FROM centos:latest
MAINTAINER quanling
CMD ["echo","hello World"]

如果使用上面的文件創(chuàng)建鏡像test:cmd，使用history命令查看容器主進(jìn)程命令，下方橙色標(biāo)記部分

[root@localhost docker]# docker history --no-trunc test:cmd
IMAGE                                                                     CREATED          CREATED BY                                                                                                                                                                                                SIZE      COMMENT
sha256:694d5f2d8809ef2847a9b6fd46efed49ab59aa6466784a1e783beb25c2f6c16e   31 seconds ago   /bin/sh -c #(nop)  CMD ["echo" "hello World"]                                                                                                                                                             0B        
sha256:6dcafb4f0c8d93e8793f84bb837ef26ed6293c156dafafbbc520e55ed601a09e   16 minutes ago   /bin/sh -c #(nop)  MAINTAINER quanling                                                                                                                                                                    0B        
sha256:5d0da3dc976460b72c77d94c8a1ad043720b0416bfc16c52c45d4847e53fadb6   3 months ago     /bin/sh -c #(nop)  CMD ["/bin/bash"]                                                                                                                                                                      0B        
<missing>                                                                 3 months ago     /bin/sh -c #(nop)  LABEL org.label-schema.schema-version=1.0 org.label-schema.name=CentOS Base Image org.label-schema.vendor=CentOS org.label-schema.license=GPLv2 org.label-schema.build-date=20210915   0B        
<missing>                                                                 3 months ago     /bin/sh -c #(nop) ADD file:805cb5e15fb6e0bb0326ca33fd2942e068863ce2a8491bb71522c652f31fb466 in / 

運(yùn)行容器后成功打印出Hello World后容器直接退出。容器狀態(tài)為Exited(0)。此時(shí)容器啟動(dòng)的主進(jìn)程為橙色標(biāo)記部分

[root@localhost docker]# docker run --name cmd test:cmd
hello World
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE      COMMAND                CREATED         STATUS                     PORTS     NAMES
6bc94359c4fd   test:cmd   "echo 'hello World'"   4 seconds ago   Exited (0) 3 seconds ago             cmd

若想讓容器一直up狀態(tài)，方便進(jìn)入容器進(jìn)一步操作，需要使用掛起命令覆蓋CMD ["echo","hello World"]，

方法1：在命令中增加綠色高亮部分代碼（額外增加-it選項(xiàng)可直接進(jìn)入容器）。進(jìn)入容器成功

[root@localhost docker]# docker run -it --name upcontainer test:cmd /bin/bash
[root@9351844319e3 /]#

更換tty窗口，查看容器狀態(tài)Up。此時(shí)容器啟動(dòng)的主進(jìn)程入橙色標(biāo)記部分，說明覆蓋CMD成功

[root@localhost ~]# docker ps -a
CONTAINER ID   IMAGE      COMMAND                CREATED          STATUS                     PORTS     NAMES
9351844319e3   test:cmd   "/bin/bash"           11 seconds ago   Up 10 seconds                         upcontainer

方法2：在命令中增加綠色高亮部分代碼（額外增加-it選項(xiàng)可直接進(jìn)入容器）。進(jìn)入容器成功

[root@localhost docker]# docker run --name upcontainer -it --entrypoint /bin/bash test:cmd 
[root@50763cf9a838 /]# 

更換tty窗口，查看容器狀態(tài)Up。此時(shí)容器啟動(dòng)的主進(jìn)程入橙色標(biāo)記部分，說明覆蓋CMD成功

[root@localhost ~]# docker ps
CONTAINER ID   IMAGE      COMMAND       CREATED              STATUS              PORTS     NAMES
50763cf9a838   test:cmd   "/bin/bash"   About a minute ago   Up About a minute             upcontainer

ENTRYPOINT

FROM centos:latest
MAINTAINER quanling
ENTRYPOINT ["echo","Hello World"]

如果使用上面的文件創(chuàng)建鏡像test:ENTRYPOINT

運(yùn)行容器后成功打印出Hello World后容器直接退出。容器狀態(tài)為Exited(0)。此時(shí)容器啟動(dòng)的主進(jìn)程入橙色標(biāo)記部分

[root@localhost docker]# docker run --name ENTRYPOINT test:ENTRYPOINT
Hello World
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE             COMMAND                CREATED         STATUS                     PORTS     NAMES
e6cf335c5c09   test:ENTRYPOINT   "echo 'Hello World'"   8 seconds ago   Exited (0) 6 seconds ago             ENTRYPOINT

若想讓容器一直up狀態(tài)，方便exec進(jìn)入容器進(jìn)一步操作，需要使用掛起命令覆蓋ENTRYPOINT["echo","hello World"]，模仿上面的操作，結(jié)果如下，容器Exited狀態(tài)（–no-trunc顯示全輸出信息）

[root@localhost docker]# docker run --name upcontainer test:ENTRYPOINT /bin/bash
Hello World /bin/bash[root@localhost docker]# docker ps -a --no-trunc
CONTAINER ID                                                       IMAGE             COMMAND                                  CREATED         STATUS                     PORTS     NAMES
0476c3014fa4c28615b72c231971c6b5186a310f9b2f5cae466643d65b236c34   test:ENTRYPOINT   "echo 'Hello World' /bin/bash"   2 minutes ago   Exited (0) 2 minutes ago             upcontainer
e6cf335c5c09df35845f40abfd81594e17b3457891128ee2108414d7573e62a3   test:ENTRYPOINT   "echo 'Hello World'"                     7 minutes ago   Exited (0) 7 minutes ago             ENTRYPOINT

我們想執(zhí)行的掛起命令并未覆蓋ENTRYPOINT命令，反而作為echo命令的參數(shù)部分一起輸出了。因?yàn)楦采wENTRYPOINT命令需要使用–entrypoint設(shè)置（額外增加-it選項(xiàng)可直接進(jìn)入容器），進(jìn)入容器成功。

[root@localhost docker]# docker run -it --entrypoint /bin/bash --name upcontainer test:ENTRYPOINT
[root@4fe14a5e7bd1 /]#

更換tty窗口，查看容器狀態(tài)Up。此時(shí)容器啟動(dòng)的主進(jìn)程入橙色標(biāo)記部分，說明覆蓋ENTRYPOINT成功

[root@localhost ~]# docker ps -a
CONTAINER ID   IMAGE             COMMAND                CREATED          STATUS                      PORTS     NAMES
4fe14a5e7bd1   test:ENTRYPOINT   "/bin/bash"            11 seconds ago   Up 10 seconds                         upcontainer
e6cf335c5c09   test:ENTRYPOINT "echo 'Hello World'" 14 minutes ago Exited (0) 14 minutes ago ENTRYPOINT

ENTRYPOINT&CMD

FROM centos:latest
MAINTAINER quanling
ENTRYPOINT ["echo"]
CMD ["hello World"]

如果使用上面的文件創(chuàng)建鏡像test:mixed。使用history命令查看容器主進(jìn)程命令，下方橙色標(biāo)記部分

[root@localhost docker]# docker history --no-trunc test:mixed
IMAGE                                                                     CREATED          CREATED BY                                                                                                                                                                                                SIZE      COMMENT
sha256:2c1f8303382cb221fac04a76234d0b1afe3a513205267afe2d01f39006877be8   24 seconds ago   /bin/sh -c #(nop)  CMD ["hello World"]                                                                                                                                                                    0B        
sha256:13608f257d7b6d1ae771af1aec482b7b87650703648a4ac5c03e8715f78c0079   25 seconds ago   /bin/sh -c #(nop)  ENTRYPOINT ["echo"]                                                                                                                                                                    0B        
sha256:6dcafb4f0c8d93e8793f84bb837ef26ed6293c156dafafbbc520e55ed601a09e   2 hours ago      /bin/sh -c #(nop)  MAINTAINER quanling                                                                                                                                                                    0B        
sha256:5d0da3dc976460b72c77d94c8a1ad043720b0416bfc16c52c45d4847e53fadb6   3 months ago     /bin/sh -c #(nop)  CMD ["/bin/bash"]                                                                                                                                                                      0B        
<missing>                                                                 3 months ago     /bin/sh -c #(nop)  LABEL org.label-schema.schema-version=1.0 org.label-schema.name=CentOS Base Image org.label-schema.vendor=CentOS org.label-schema.license=GPLv2 org.label-schema.build-date=20210915   0B        
<missing>                                                                 3 months ago     /bin/sh -c #(nop) ADD file:805cb5e15fb6e0bb0326ca33fd2942e068863ce2a8491bb71522c652f31fb466 in /                                                                                                          231MB

運(yùn)行容器后成功打印出Hello World后容器直接退出。容器狀態(tài)為Exited(0)。此時(shí)容器啟動(dòng)的主進(jìn)程為橙色標(biāo)記部分

[root@localhost docker]# docker run --name mixed test:mixed
hello World
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE      COMMAND                CREATED         STATUS                     PORTS     NAMES
22362d314132   test:mixed   "echo 'hello World'"   4 seconds ago   Exited (0) 3 seconds ago             mixed

若想讓容器一直up狀態(tài)，方便進(jìn)入容器進(jìn)一步操作，需要覆蓋Etrypoint和CMD中命令，在命令中增加綠色高亮部分代碼（額外增加-it選項(xiàng)可直接進(jìn)入容器）。查看執(zhí)行結(jié)果

[root@localhost docker]# docker run -it --name upcontainer test:mixed /bin/bash
/bin/bash
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE        COMMAND                CREATED         STATUS                     PORTS     NAMES
df18afb54646   test:mixed   "echo /bin/bash"       6 seconds ago   Exited (0) 5 seconds ago             upcontainer
22362d314132   test:mixed   "echo 'hello World'"   3 minutes ago   Exited (0) 3 minutes ago             mixed

執(zhí)行發(fā)現(xiàn)容器為Exited狀態(tài)，打印出“/bin/bash”后容器退出。說明該操作僅僅覆蓋了CMD ["hello World"]部分，保留了ENTRYPOINT ["echo"]部分。正確的操作應(yīng)該使用–entrypoint設(shè)置（額外增加-it選項(xiàng)可直接進(jìn)入容器），進(jìn)入容器成功。

[root@localhost docker]# docker run -it --entrypoint /bin/bash --name upcontainer test:mixed 
[root@deb56cf88e89 /]#

更換tty窗口，查看容器狀態(tài)Up。此時(shí)容器啟動(dòng)的主進(jìn)程入橙色標(biāo)記部分，說明覆蓋ENTRYPOINT成功

[root@localhost ~]# docker ps -a
CONTAINER ID   IMAGE        COMMAND                CREATED              STATUS                     PORTS     NAMES
deb56cf88e89   test:mixed   "/bin/bash"            About a minute ago   Up About a minute                   upcontainer
22362d314132   test:mixed   "echo 'hello World'"   8 minutes ago        Exited (0) 8 minutes ago             mixed

docker-compose中的覆蓋主進(jìn)程命令

有些容器是使用docker-compose來啟動(dòng)容器的，按照Dockerfile文件的不同，docker-compose中的修改不同，覆蓋命令 tail -f /dev/null

利用上面三個(gè)鏡像，編寫docker-compose.yml文件

version: '3'
services:
  cmd:
    image: test:cmd
    container_name: cmd
  ENTRYPOINT:
    image: test:ENTRYPOINT
    container_name: ENTRYPOINT
  mixed:
    image: test:mixed
    container_name: mixed

啟動(dòng)三個(gè)鏡像的服務(wù)容器，都執(zhí)行后退出Exited狀態(tài)。容器主進(jìn)程見下方橙色高亮部分

[root@localhost docker]# docker-compose up -d
Starting cmd        ... done
Creating ENTRYPOINT ... done
Creating mixed      ... done
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE             COMMAND                CREATED          STATUS                      PORTS     NAMES
7519cbfb6ef8   test:mixed        "echo 'hello World'"   40 seconds ago   Exited (0) 36 seconds ago             mixed
d1c2709a0173   test:ENTRYPOINT   "echo 'Hello World'"   40 seconds ago   Exited (0) 36 seconds ago             ENTRYPOINT
e2206ea2cfc1   test:cmd          "echo 'hello World'"   2 minutes ago    Exited (0) 37 seconds ago             cmd

Entrypoint命令

在docker-compose.yaml 文件中每個(gè)服務(wù)下添加以下綠色高亮區(qū)域命令，以覆蓋原來docker中的命令

version: '3'
services:
  cmd:
    image: test:cmd
    container_name: cmd
    entrypoint:
    - tail
    - -f
    - /dev/null
  ENTRYPOINT:
    image: test:ENTRYPOINT
    container_name: ENTRYPOINT
    entrypoint:
    - tail
    - -f
    - /dev/null
  mixed:
    image: test:mixed
    container_name: mixed
    entrypoint:
    - tail
    - -f
    - /dev/null

重新啟動(dòng)容器，容器全部為up狀態(tài)，主程序命令被替換為"tail -f /dev/null"

[root@localhost docker]# docker-compose up -d
Starting mixed        ... done
Starting cmd          ... done
Recreating ENTRYPOINT ... done
[root@localhost docker]# docker ps -a
CONTAINER ID   IMAGE             COMMAND               CREATED          STATUS          PORTS     NAMES
2d4682226bb0   test:cmd          "tail -f /dev/null"   4 seconds ago    Up 2 seconds              cmd
c3870ab0d462   test:mixed        "tail -f /dev/null"   31 seconds ago   Up 28 seconds             mixed
7320deecd45a   test:ENTRYPOINT   "tail -f /dev/null"   59 seconds ago   Up 55 seconds             ENTRYPOINT

在docker-compose.yaml 文件中每個(gè)服務(wù)下添加以下綠色高亮區(qū)域命令

version: '3'
services:
  cmd:
    image: test:cmd
    container_name: cmd
    command: tail -f /dev/null
  ENTRYPOINT:
    image: test:ENTRYPOINT
    container_name: ENTRYPOINT
    command: tail -f /dev/null
  mixed:
    image: test:mixed
    container_name: mixed
    command: tail -f /dev/null

重新啟動(dòng)容器，查看容器狀態(tài)，及主程序命令

[root@localhost docker]# docker-compose up -d
cmd is up-to-date  ... done
Recreating ENTRYPOINT ... done
Recreating mixed      ... done
[root@localhost docker]# docker ps -a --no-trunc
CONTAINER ID                                                       IMAGE             COMMAND                                  CREATED              STATUS                          PORTS     NAMES
bf67da0ba9815a013a2005d61daa223e31586bf1cde279933ba71d0148c721ff   test:mixed        "echo tail -f /dev/null"                 About a minute ago   Exited (0) About a minute ago             mixed
f019610b1aedb54904704227ae661f421786b72ecc9e3b35154442c4717afcb0   test:ENTRYPOINT   "echo 'Hello World' tail -f /dev/null"   About a minute ago   Exited (0) About a minute ago             ENTRYPOINT
224bc6db4563531c68947a38acbf3418c43149b2ef6a92565f940a98ab1a9b1e   test:cmd          "tail -f /dev/null"                      10 minutes ago       Up 10 minutes                             cmd

分析結(jié)論

使用commad命令，結(jié)果僅test:cmd中命令被替換；test:Entrypoint鏡像未被覆蓋，且commad命令作為參數(shù)傳入；test:mixed鏡像僅CMD部分命令被替換，ENTRYPOINT部分未被替換。與docker run運(yùn)行結(jié)果一致。

補(bǔ)充

容器up狀態(tài)時(shí)，執(zhí)行exec命令進(jìn)入容器

# docker exec -it  容器名 /bin/bash

容器內(nèi)查看相關(guān)配置是否符合預(yù)期，手動(dòng)執(zhí)行鏡像原entrypoint/cmd命令跟著日志進(jìn)行調(diào)試

鏡像往往很精簡，不包含yum、vi 等命令，導(dǎo)致需要修改配置進(jìn)行調(diào)試受阻，除安裝所需命令這個(gè)麻煩的方法外，還可以在容器外使用docker cp命令

$ docker cp 容器名:文件完整路徑 本地路徑 #容器內(nèi)文件copy到本地

$ docker cp 本地文件容器名:文件完整路徑 #本地文件copy到容器內(nèi)

$ docker run -it –rm –entrypoint="" 容器名 /bin/bash