### USER 指定当前用户 格式：`USER <用户名>` `USER` 指令和 `WORKDIR` 相似，都是改变环境状态并影响以后的层。`WORKDIR` 是改变工作目录，`USER` 则是改变之后层的执行 `RUN`, `CMD` 以及 `ENTRYPOINT` 这类命令的身份。 当然，和 `WORKDIR` 一样，`USER` 只是帮助你切换到指定用户而已，这个用户必须是事先建立好的，否则无法切换。 ``` <pre class="prettyprint"><ol class="linenums"><li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">RUN groupadd </span><span class="pun">-</span><span class="pln">r redis </span><span class="pun">&&</span><span class="pln"> useradd </span><span class="pun">-</span><span class="pln">r </span><span class="pun">-</span><span class="pln">g redis redis</span></code></li> <li class="l1"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">USER redis</span></code></li> <li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">RUN </span><span class="pun">[</span><span class="pln"> </span><span class="str">"redis-server"</span><span class="pln"> </span><span class="pun">]</span></code></li> </ol> ``` 如果以 `root` 执行的脚本，在执行期间希望改变身份，比如希望以某个已经建立好的用户来运行某个服务进程，不要使用 `su` 或者 `sudo`，这些都需要比较麻烦的配置，而且在 TTY 缺失的环境下经常出错。建议使用 [`gosu`](https://github.com/tianon/gosu)。 ``` <pre class="prettyprint"><ol class="linenums"><li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="com"># 建立 redis 用户，并使用 gosu 换另一个用户执行命令</span></code></li> <li class="l1"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">RUN groupadd </span><span class="pun">-</span><span class="pln">r redis </span><span class="pun">&&</span><span class="pln"> useradd </span><span class="pun">-</span><span class="pln">r </span><span class="pun">-</span><span class="pln">g redis redis</span></code></li> <li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="com"># 下载 gosu</span></code></li> <li class="l1"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">RUN wget </span><span class="pun">-</span><span class="pln">O </span><span class="pun">/</span><span class="pln">usr</span><span class="pun">/</span><span class="kwd">local</span><span class="pun">/</span><span class="pln">bin</span><span class="pun">/</span><span class="pln">gosu </span><span class="str">"https://github.com/tianon/gosu/releases/download/1.7/gosu-amd64"</span><span class="pln"> \</span></code></li> <li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln"> </span><span class="pun">&&</span><span class="pln"> chmod </span><span class="pun">+</span><span class="pln">x </span><span class="pun">/</span><span class="pln">usr</span><span class="pun">/</span><span class="kwd">local</span><span class="pun">/</span><span class="pln">bin</span><span class="pun">/</span><span class="pln">gosu \</span></code></li> <li class="l1"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln"> </span><span class="pun">&&</span><span class="pln"> gosu nobody </span><span class="kwd">true</span></code></li> <li class="l"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="com"># 设置 CMD，并以另外的用户执行</span></code></li> <li class="l1"><code class="pcalibre10 pcalibre11 pcalibre9"><span class="pln">CMD </span><span class="pun">[</span><span class="pln"> </span><span class="str">"exec"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"gosu"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"redis"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"redis-server"</span><span class="pln"> </span><span class="pun">]</span></code></li> </ol> ```