docker container 的生命周期

当我们创建一个 container 的时候, 它的生命过程中都会经历哪几个阶段呢? 有时候明明一个 container 已经死了, 我们去创建一个同名 container 的时候, 它竟然说有一个同名的 container 存在? 明白了 container 的生命周期, 就能理解了.

container 的生命阶段

一个 docker container 从创建到彻底消亡, 可能会经过的阶段:
docker_container_lifecycle.png

  1. created: container 被创建, 但是没有被启动
  2. running: container 被启动, 里面的进程在运行
  3. paused: container 里的所有进程被挂起, 暂停运行
  4. stopped: container 里面的进程被杀死, container 还存在
  5. deleted: container 被彻底删除

下面我们就以 nginx 做container 为例来说明这个过程.

create 创建 container

下面创建一个 nginx container, 并使用 ps -l (--latest) 来查看, 状态是 Created.

supra@suprabox:~$ docker create --name nginxServer nginx
ac301e1f4f3f3ba5631ff5d7f3276d1544610229a9e3727dac6d5f66181bfe05

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS    PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   1 minutes ago   Created             nginxServer

start 启动 container

通过start子命令启动 container, 然后通过ps子命令查看状态. 通过exec子命令写一句话到/text.txt文件, 并且查看写入内容.

supra@suprabox:~$ docker start nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS         PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   25 minutes ago   Up 5 seconds   80/tcp    nginxServer

supra@suprabox:~$ docker exec nginxServer bash -c 'echo "this is a test" > /test.txt'
supra@suprabox:~$ docker exec nginxServer cat  /test.txt
this is a test

pause 暂停 container

可以看到经过 pause 之后, 状态变为 Paused. 如果尝试进入这个 container exec, 这个时候会报错.

supra@suprabox:~$ docker pause nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS                  PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   29 minutes ago   Up 4 minutes (Paused)   80/tcp    nginxServer

supra@suprabox:~$ docker exec -it nginxServer bash
Error response from daemon: Container nginxServer is paused, unpause the container before exec

unpause 继续 container

supra@suprabox:~$ docker unpause nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED             STATUS          PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   About an hour ago   Up 44 minutes   80/tcp    nginxServer

stop 停止 container

stop 之后, 通过docker ps -l 可以看到状态变为 Exited, 这个时候通过docker logs 仍旧能看到之前的log, 并且可以看到主进程被杀死的日志. 但是通过docker exec 已经无法进入 container.

supra@suprabox:~$ docker stop nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED             STATUS                     PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   About an hour ago   Exited (0) 8 seconds ago             nginxServer

supra@suprabox:~$ docker logs -f nginxServer
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
...
2023/01/27 13:35:52 [notice] 1#1: signal 17 (SIGCHLD) received from 32
2023/01/27 13:35:52 [notice] 1#1: worker process 32 exited with code 0
2023/01/27 13:35:52 [notice] 1#1: worker process 37 exited with code 0
2023/01/27 13:35:52 [notice] 1#1: exit

supra@suprabox:~$ docker exec -it nginxServer bash
Error response from daemon: Container ac301e1f4f3f3ba5631ff5d7f3276d1544610229a9e3727dac6d5f66181bfe05 is not running

start 重新启动 stop 的 container

通过 start 子命令, 可以重新启动 stop 的container, 通过docker ps -l 可以看到它的状态是刚起来4秒. 这时候去查看之前写入的 /test.txt 文件, 内容还在. 但是这时候里面的进程都是新启动的, 不说 stop 之前的那个(批)进程了.

supra@suprabox:~$ docker start nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED             STATUS         PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   About an hour ago   Up 4 seconds   80/tcp    nginxServer

supra@suprabox:~$ docker exec nginxServer cat  /test.txt
this is a test

rm 彻底删除container

可以通过rm子命令删除任何状态的container. 如果一个container 是 stopped 或 created 状态的, 可以直接rm, 否则就必须通过 -f 强制删除.

docker rm nginxServer
docker rm -f nginxServer

run 创建同时启动container

可以通过 run 子命令, 在创建container的同时, 启动container, 相当于同时执行了create和start.

supra@suprabox:~$ docker run --name nginxServer1 --rm  nginx
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/

kill 杀掉一个运行的container

通过kill 杀掉一个运行的container 之后, container 进入 stopped 的状态.

supra@suprabox:~$ docker kill nginxServer
nginxServer

supra@suprabox:~$ docker ps -l
CONTAINER ID   IMAGE     COMMAND                  CREATED       STATUS                        PORTS     NAMES
ac301e1f4f3f   nginx     "/docker-entrypoint.…"   2 hours ago   Exited (137) 18 seconds ago             nginxServer

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