问题：执行docker run ubuntu 后，容器处于 exited 状态，希望能够出入up状态，可以exec进去查看

原因： docker容器执行任务完成后就会处于exited状态

操作系统：centos7

[root@mapleaves k8s-test]# docker run -d --name ubuntu ubuntu
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
5b7339215d1d: Pull complete 
14ca88e9f672: Pull complete 
a31c3b1caad4: Pull complete 
b054a26005b7: Pull complete 
Digest: sha256:9b1702dcfe32c873a770a32cfd306dd7fc1c4fd134adfb783db68defc8894b3c
Status: Downloaded newer image for ubuntu:latest
0f790e3bc43855d97347d91f2c54a4f47d4c4aa2e87ac2d5fe03c451374b34eb
[root@mapleaves k8s-test]# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
[root@mapleaves k8s-test]# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                      PORTS               NAMES
0f790e3bc438        ubuntu              "/bin/bash"         12 seconds ago      Exited (0) 11 seconds ago                       ubuntu

方法1: 使用 docker run -dit

[root@mapleaves k8s-test]# docker run -dit --name ubuntu ubuntu
faa5fcdcf5256382f4b739e4da5dc212bed5d5b7e93428ae22bd89866853077e
[root@mapleaves k8s-test]# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
faa5fcdcf525        ubuntu              "/bin/bash"         3 seconds ago       Up 2 seconds                            ubuntu

方法2：执行一个循环或者不会段的任务 

[root@mapleaves ~]# docker run -d --name ubuntu2 ubuntu sleep infinity
[root@mapleaves ~]# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
dbfe1b787584        ubuntu              "sleep infinity"    57 seconds ago      Up 56 seconds                           ubuntu2
faa5fcdcf525        ubuntu              "/bin/bash"         10 minutes ago      Up 10 minutes                           ubuntu

参考链接：

https://stackoverflow.com/questions/28212380/why-docker-container-exits-immediately