docker具名挂载和匿名挂载

# docker具名挂载和匿名挂载

[TOC]

## 按路径挂载

```bash
docker run -d --name nginx03 -P -v /home/xxx/conf/nginx:/etc/nginx nginx
```

## 具名挂载

* 以下命令会将容器内的/etc/nginx挂载到/var/lib/docker/volume/卷名/_data，这里卷名就是etc-nginx：

```bash
$ docker run -d --name nginx01 -P -v etc-nginx:/etc/nginx nginx
$ ll /var/lib/docker/volumes/etc-nginx/_data/
总用量 36
drwxr-xr-x 3 root root 4096 2月  13 13:43 ./
drwx-----x 3 root root 4096 2月  13 13:43 ../
drwxr-xr-x 2 root root 4096 2月  13 13:43 conf.d/
-rw-r--r-- 1 root root 1007 12月 28 23:28 fastcgi_params
-rw-r--r-- 1 root root 5349 12月 28 23:28 mime.types
lrwxrwxrwx 1 root root   22 12月 28 23:40 modules -> /usr/lib/nginx/modules
-rw-r--r-- 1 root root  648 12月 28 23:40 nginx.conf
-rw-r--r-- 1 root root  636 12月 28 23:28 scgi_params
-rw-r--r-- 1 root root  664 12月 28 23:28 uwsgi_params
```

* 执行以下命令，具名挂载会显示卷名：

```bash
$ docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS         PORTS                                     NAMES
ebeea9cf1fa9   nginx     "/docker-entrypoint.…"   5 minutes ago   Up 5 minutes   0.0.0.0:49153->80/tcp, :::49153->80/tcp   nginx01
$ docker inspect ebeea9cf1fa9
        "Mounts": [
            {
                "Type": "volume",
                "Name": "etc-nginx",
                "Source": "/var/lib/docker/volumes/etc-nginx/_data",
                "Destination": "/etc/nginx",
                "Driver": "local",
                "Mode": "z",
                "RW": true,
                "Propagation": ""
            }
        ],
...
$ docker volume ls
DRIVER    VOLUME NAME
...
local     etc-nginx
...
```

## 匿名挂载

* 匿名挂载不需要写宿主机上的路径，挂载路径也在/var/lib/docker/volume/目录下，但卷名是一长串随机字符串：

```bash
$ docker run -d --name nginx02 -P -v /etc/nginx nginx
$ docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS          PORTS                                     NAMES
d476391f6231   nginx     "/docker-entrypoint.…"   24 seconds ago   Up 24 seconds   0.0.0.0:49154->80/tcp, :::49154->80/tcp   nginx02
$ docker inspect d476391f6231
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "a090507e20d344f9298731b769728d252b7c43ef1dc1c80e520c82be761db578",
                "Source": "/var/lib/docker/volumes/a090507e20d344f9298731b769728d252b7c43ef1dc1c80e520c82be761db578/_data",
                "Destination": "/etc/nginx",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
...
```

### 通过Dockerfile匿名挂载

```Dockerfile
$ cat dockerfile01
FROM centos

ENTRYPOINT ["/bin/bash"]

VOLUME ["volume01", "volume02"]

RUN echo "----end build----"
$ docker build -f dockerfile01 -t scott/centos:1.0 .
Sending build context to Docker daemon  2.048kB
Step 1/4 : FROM centos
latest: Pulling from library/centos
a1d0c7532777: Pull complete
Digest: sha256:a27fd8080b517143cbbbab9dfb7c8571c40d67d534bbdee55bd6c473f432b177
Status: Downloaded newer image for centos:latest
 ---> 5d0da3dc9764
Step 2/4 : ENTRYPOINT ["/bin/bash"]
 ---> Running in 5744a7751935
Removing intermediate container 5744a7751935
 ---> 00364df73617
Step 3/4 : VOLUME ["volume01", "volume02"]
 ---> Running in 664616219d10
Removing intermediate container 664616219d10
 ---> 8cf7bd193272
Step 4/4 : RUN echo "----end build----"
 ---> Running in 4e6d012837e5
----end build----
Removing intermediate container 4e6d012837e5
 ---> fee57adc730f
Successfully built fee57adc730f
Successfully tagged scott/centos:1.0
$ docker images
REPOSITORY     TAG       IMAGE ID       CREATED              SIZE
scott/centos   1.0       fee57adc730f   About a minute ago   231MB
$ docker run -itd --name "centos01" scott/centos:1.0
```

### 数据卷容器

* 几个容器共享一个数据，最开始创建的容器叫父容器，不过删除父容器也不会删除创建的卷。
* 将上面创建的centos01容器作为父容器，创建centos02容器，和centos01共享volume01、volume02两个数据卷。

```bash
$ docker run -itd --name "centos02" --volumes-from centos01 scott/centos:1.0
$ docker ps
CONTAINER ID   IMAGE              COMMAND                  CREATED          STATUS          PORTS                                     NAMES
4ca1f2787be4   scott/centos:1.0   "/bin/bash"              3 minutes ago    Up 3 minutes                                              centos02
c2dad2c92f3a   scott/centos:1.0   "/bin/bash"              5 minutes ago    Up 5 minutes                                              centos01
$ docker inspect 4ca1f2787be4
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c",
                "Source": "/var/lib/docker/volumes/afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c/_data",
                "Destination": "volume02",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            },
            {
                "Type": "volume",
                "Name": "bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e",
                "Source": "/var/lib/docker/volumes/bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e/_data",
                "Destination": "volume01",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
...
$ docker inspect c2dad2c92f3a
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e",
                "Source": "/var/lib/docker/volumes/bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e/_data",
                "Destination": "volume01",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            },
            {
                "Type": "volume",
                "Name": "afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c",
                "Source": "/var/lib/docker/volumes/afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c/_data",
                "Destination": "volume02",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
...
```

* 如果挂载的卷是父容器的子集，例如dockerfile02如下，则使用--volumes-from仍然会和父容器共享卷：

```bash
$ cat dockerfile02
FROM centos

ENTRYPOINT ["/bin/bash"]

VOLUME ["volume01"]

RUN echo "----end build----"
$ docker build -f dockerfile02 -t scott/centos:1.1 .
$ docker run -itd --name "centos03" --volumes-from centos01 scott/centos:1.1
$ docker ps
CONTAINER ID   IMAGE              COMMAND                  CREATED          STATUS          PORTS                                     NAMES
0d66742336f0   scott/centos:1.1   "/bin/bash"              7 minutes ago    Up 7 minutes                                              centos03
$ docker inspect 0d66742336f0
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e",
                "Source": "/var/lib/docker/volumes/bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e/_data",
                "Destination": "volume01",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            },
            {
                "Type": "volume",
                "Name": "afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c",
                "Source": "/var/lib/docker/volumes/afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c/_data",
                "Destination": "volume02",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
...
```

* 如果挂载的卷是父容器的超集，例如要挂载volume01、volume02、volume03三个匿名卷，使用--volumes-from会使volume01、volume02和父容器共享，但volume03由于父容器没有创建，所以会创建：

```
...
$ docker inspect 9c24bbf78668
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "8c6b227a247371dddb4cd9e1914d33c186ee7f82646a3efa2851971bc0abc310",
                "Source": "/var/lib/docker/volumes/8c6b227a247371dddb4cd9e1914d33c186ee7f82646a3efa2851971bc0abc310/_data",
                "Destination": "volume03",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            },
            {
                "Type": "volume",
                "Name": "bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e",
                "Source": "/var/lib/docker/volumes/bf710817e8daa8ffe052fbe8f1a9de364eb95b191900c5c2025aa6d85a87234e/_data",
                "Destination": "volume01",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            },
            {
                "Type": "volume",
                "Name": "afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c",
                "Source": "/var/lib/docker/volumes/afffdb0871ea75696ef2f08458312aba26474c665b2246044adedd61b6950a5c/_data",
                "Destination": "volume02",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
...
```

* centos02使用--volumes-from继承centos01，centos03使用--volumes-from继承centos02，三者的卷都是共享的。
* 所有容器都使用`docker rm -f`命令删掉后，卷在宿主机上仍然存在。

```bash
$ docker ps -q | xargs docker rm -f
```

## 卷的权限

* 卷默认是可读写的，即宿主机和容器都能修改卷中的内容。
* 要使卷是只读的，即只允许宿主机修改卷中的内容，不允许容器修改卷中的内容，要显式指定卷是ro（read only）的，不过这种写法不适合匿名挂载，只适合指定宿主机目录的挂载和具名挂载：

```bash
$ docker run -itd --name "centos01" -v /etc:/etc/:ro centos
...
$ docker exec -it 99893fcbd412 bash
bash-4.4# mount | grep etc
/dev/sda5 on /etc type ext4 (ro,relatime,errors=remount-ro)
/dev/sda5 on /etc/hostname type ext4 (rw,relatime,errors=remount-ro)
/dev/sda5 on /etc/hosts type ext4 (rw,relatime,errors=remount-ro)
```

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