在当前目录下面创建Dockerfile文件，然后在VOLUME指令来给镜像添加一个或多个数据卷。VOLUME语法如下：
VOLUME[“/dataVolumeContainer1”, “/dataVolumeContainer2”, “/dataVolumeContainer3”]
说明：出于可移植和分享的考虑，用“-v主机目录:容器目录”这种方法不能够直接在Dockerfile中显示。由于宿主机目录是依赖于特定宿主机的，并不能够保证在所有的宿主机上都存在这样的特定目录。
实例：根据定义的Dockerfile去创建镜像。
(1) 在当前秒目录下面创建Dockerfile，内容如下：
# volume test FROM centos VOLUME ["/dataVolumeContainer1", "/dataVolumeContainer2"] CMD echo "finished......success" CMD /bin/bash
如下图：
[root@localhost ~]# vim Dockerfile [root@localhost ~]# cat Dockerfile # volume test FROM centos VOLUME ["/dataVolumeContainer1", "/dataVolumeContainer2"] CMD echo "finished......success" CMD /bin/bash
(2) 根据上面创建好的Dockerfile文件构建一个新的镜像。执行“docker build -f ./Dockerfile -t mycentos .”命令去创建镜像。如下：
[root@localhost ~]# docker build -f ./Dockerfile -t mycentos . Sending build context to Docker daemon 28.67kB Step 1/4 : FROM centos ---> 9f38484d220f Step 2/4 : VOLUME ["/dataVolumeContainer1", "/dataVolumeContainer2"] ---> Using cache ---> 7d440f43e039 Step 3/4 : CMD echo "finished......success" ---> Using cache ---> 4814b80b83b4 Step 4/4 : CMD /bin/bash ---> Using cache ---> 1b896063f266 Successfully built 1b896063f266 Successfully tagged mycentos:latest
我们可以使用“docker images”命令查看我们刚刚创建的镜像（镜像ID为1b896063f266）：
[root@localhost ~]# docker images REPOSITORY TAG IMAGE ID CREATED SIZE mycentos latest 1b896063f266 3 days ago 202MB tomcat latest 5377fd8533c3 2 weeks ago 506MB centos latest 9f38484d220f 3 months ago 202MB hello-world latest fce289e99eb9 6 months ago 1.84kB
(3) 使用“docker run -it 镜像”启动镜像。如下：
[root@localhost ~]# docker run -it mycentos [root@7fe9af3b60b9 /]# ll total 12 -rw-r--r--. 1 root root 12082 Mar 5 17:36 anaconda-post.log lrwxrwxrwx. 1 root root 7 Mar 5 17:34 bin -> usr/bin drwxr-xr-x. 2 root root 6 Jun 30 14:10 dataVolumeContainer1 drwxr-xr-x. 2 root root 6 Jun 30 14:10 dataVolumeContainer2 drwxr-xr-x. 5 root root 360 Jun 30 14:10 dev drwxr-xr-x. 1 root root 66 Jun 30 14:10 etc drwxr-xr-x. 2 root root 6 Apr 11 2018 home lrwxrwxrwx. 1 root root 7 Mar 5 17:34 lib -> usr/lib lrwxrwxrwx. 1 root root 9 Mar 5 17:34 lib64 -> usr/lib64 drwxr-xr-x. 2 root root 6 Apr 11 2018 media drwxr-xr-x. 2 root root 6 Apr 11 2018 mnt drwxr-xr-x. 2 root root 6 Apr 11 2018 opt dr-xr-xr-x. 125 root root 0 Jun 30 14:10 proc dr-xr-x---. 2 root root 114 Mar 5 17:36 root drwxr-xr-x. 11 root root 148 Mar 5 17:36 run lrwxrwxrwx. 1 root root 8 Mar 5 17:34 sbin -> usr/sbin drwxr-xr-x. 2 root root 6 Apr 11 2018 srv dr-xr-xr-x. 13 root root 0 Jun 24 13:42 sys drwxrwxrwt. 7 root root 132 Mar 5 17:36 tmp drwxr-xr-x. 13 root root 155 Mar 5 17:34 usr drwxr-xr-x. 18 root root 238 Mar 5 17:34 var
上图中，我们可以看见“dataVolumeContainer1”和“dataVolumeContainer2”目录，这就是Dockerfile创建数据卷。
问题：我们怎样查看上面“dataVolumeContainer1”和“dataVolumeContainer2”两个目录，对应宿主机对应的目录呢？
[root@localhost ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7fe9af3b60b9 mycentos "/bin/sh -c /bin/bash" 58 seconds ago Up 57 seconds mystifying_villani
[root@localhost ~]# docker inspect 7fe9af3b60b9
[
{
...
"Mounts": [
{
"Type": "volume",
"Name": "0b92644824def28ba0d88ef0b8ed169631305a4a91502b64cda70153e116cac6",
"Source": "/var/lib/docker/volumes/0b92644824def28ba0d88ef0b8ed169631305a4a91502b64cda70153e116cac6/_data",
"Destination": "/dataVolumeContainer2",
"Driver": "local",
"Mode": "",
"RW": true,
"Propagation": ""
},
{
"Type": "volume",
"Name": "931c1d7a053f23b3292893b35d46a6fe9fae789451fa1ff84e3aad1f255b1cc5",
"Source": "/var/lib/docker/volumes/931c1d7a053f23b3292893b35d46a6fe9fae789451fa1ff84e3aad1f255b1cc5/_data",
"Destination": "/dataVolumeContainer1",
"Driver": "local",
"Mode": "",
"RW": true,
"Propagation": ""
}
],
...
}
]
[root@localhost ~]#上面描述了“dataVolumeContainer1”和“dataVolumeContainer2”目录映射到宿主主机的目录。
注意：如果向数据卷写入数据抛出“cannot open directory .: Permission denied”错误。解决办法：在挂载的目录后多加一个“--privileged=true”参数即可。
privileged
/'prɪvəlɪdʒd/
adj. 享有特权的；有特别恩典的
v. 给予…特权；免除（privilege的过去分词）
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