# 守护态运行

更多的时候，需要让 Docker 在后台运行而不是直接把执行命令的结果输出在当前宿主机下。此时，可以通过添加 `-d` 参数来实现。

下面举两个例子来说明一下。

如果不使用 `-d` 参数运行容器。

```bash
$ docker run ubuntu:18.04 /bin/sh -c "while true; do echo hello world; sleep 1; done"
hello world
hello world
hello world
hello world
```

容器会把输出的结果 (STDOUT) 打印到宿主机上面

如果使用了 `-d` 参数运行容器。

```bash
$ docker run -d ubuntu:18.04 /bin/sh -c "while true; do echo hello world; sleep 1; done"
77b2dc01fe0f3f1265df143181e7b9af5e05279a884f4776ee75350ea9d8017a
```

此时容器会在后台运行并不会把输出的结果 (STDOUT) 打印到宿主机上面(输出结果可以用 `docker logs` 查看)。

**注：** 容器是否会长久运行，是和 `docker run` 指定的命令有关，和 `-d` 参数无关。

使用 `-d` 参数启动后会返回一个唯一的 id，也可以通过 `docker container ls` 命令来查看容器信息。

```
$ docker container ls
CONTAINER ID  IMAGE         COMMAND               CREATED        STATUS       PORTS NAMES
77b2dc01fe0f  ubuntu:18.04  /bin/sh -c 'while tr  2 minutes ago  Up 1 minute        agitated_wright
```

要获取容器的输出信息，可以通过 `docker container logs` 命令。

```bash
$ docker container logs [container ID or NAMES]
hello world
hello world
hello world
. . .
```


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