# USER

```
USER <user>[:<group>]
```

或

```
USER <UID>[:<GID>]
```

当运行一个镜像时，**USER指令**可以用来设置一个**用户名（UID）**&#x548C;可选的**用户组（或GID**）。任何跟随在该指令之后的**RUN，CMD**和**ENTRYPOINT指令**都会按照设置的**用户**和**用户组权限**运行。

**NOTE:**

当为用户指定一个组时，用户将只有指定组的成员关系。已经配置的任何其他组成员关系都将被忽略。

**WARNING:**

当用户没有一个主组时，那么镜像（或者下一条指令）将通过root组身份运行。

在**windows**上，如果不存在一个内建的账户，那么必须先创建一个用户。这可以通过作为**Dockerfile**的一部分被调用的**net user**命令来完成。

```
FROM microsoft/windowsservercore
# Create Windows user in the container
RUN net user /add patrick
# Set it for subsequent commands
USER patrick
```

demo:

```
FROM centos:7
RUN useradd -u 9000 Yang; groupadd -g 9100 ChangZhou #创建用户和用户组，否则系统中不存在该信息
USER 9000:9100
RUN mkdir /tmp/my_dir && cd /tmp/my_dir/ && touch file
CMD ["/bin/echo", "process finished"]
```

检查文件信息：

```bash
[Yang@b21fa1fb48f9 tmp]$ ll
total 8
-rwx------ 1 root root       836 Nov 13 01:55 ks-script-DrRL8A
drwxr-xr-x 2 Yang ChangZhou 4096 Mar  7 03:45 my_dir
-rw------- 1 root root         0 Nov 13 01:53 yum.log
[Yang@b21fa1fb48f9 tmp]$
```

上面的结果显示，目录根据我们设置的**用户名**和**组名**被创建了。在**Dockerfile**中引用**用户**和**用户组**时，记得得在基础镜像的系统中先创建该**用户**和**用户组**。


---

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