六、Docker：数据卷

约定不等于承诺〃 2023-01-19 04:33 54阅读 0赞

## 六、数据卷 ##

解决容器和系统的资源隔离问题。

### 什么是数据卷 ###

docker中的数据如何保存？

如果数据都放在容器内部，容器删除后，数据就会丢失了。需求：数据可以持久化。

如果安装了一个mysql容器，容器删除，数据必须还在。需求：容器数据存在的宿主机。

什么是数据卷技术？容器直接可以有一个数据共享技术，docker容器中产生的数据，同步到本地宿主机。这就是数据卷技术。使用目录挂载，将容器内部的目录挂载到linux上即可。

![image-20210506173442098][]

总结：数据卷解决容器数据的持久化和同步操作！容器之间也可以数据共享！

### 如何使用数据卷 ###

#### 方式一：直接使用命令挂载 -v ####

[root@localhost ~]# 
    [root@localhost ~]# docker ps 
    CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
    [root@localhost ~]# 
    [root@localhost ~]# ls /local # 宿主机没有该目录
    ls: cannot access /local: No such file or directory
    [root@localhost ~]# 
    # 使用-v挂载，将宿主机的/local目录和容器的/home目录进行映射
    [root@localhost ~]# docker run -it -v /local:/home centos /bin/bash 
    [root@bc9c7875eb78 /]# 
    [root@bc9c7875eb78 /]# ls /home/ # 查看容器内的/home目录
    [root@bc9c7875eb78 /]# 
    [root@bc9c7875eb78 /]# touch /home/test.java # 在home下面创建文件
    [root@bc9c7875eb78 /]# 
    [root@bc9c7875eb78 /]# ls /home/ 
    test.java
    [root@bc9c7875eb78 /]#
    
    # 宿主机查看结果 
    [root@localhost ~]# ls /local/ # 容器启动后会自动创建该目录
    test.java
    [root@localhost ~]# 
    # 容器停止后，依然可以通过宿主机操作该目录。当容器重启后可以看到相关的修改。数据会自动同步。
    
    # 查看容器挂载信息
    [root@localhost ~]# docker ps 
    CONTAINER ID   IMAGE     COMMAND       CREATED          STATUS          PORTS     NAMES
    b5992d9af84d   centos    "/bin/bash"   31 seconds ago   Up 30 seconds             sharp_ramanujan
    [root@localhost ~]# 
    [root@localhost ~]# 
    [root@localhost ~]# docker inspect b5992d9af84d # 查看容器信息
            "Mounts": [
                { 
                    "Type": "bind",
                    "Source": "/local",  # 宿主机地址
                    "Destination": "/home", # docker内地址
                    "Mode": "",
                    "RW": true,
                    "Propagation": "rprivate"
                }
            ],

**实战：安装mysql**

容器中/data目录是存储mysql的数据的，需要将/data目录挂载到宿主机上，防止数据丢失。

注意点：1.将配置文件映射出来；2.将数据映射出来；3.密码处理

[root@localhost ~]# docker run -d -p 3306:3306 -v /home/mysql/conf:/etc/mysql/conf.d -v /home/mysql/data:/var/lib/mysql --name mysql01 -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7

即使使用`docker rm 容器id` 删除了容器，mysql的数据依然存在。

直接挂载分两种：**匿名挂载和具名挂载**

# -v /宿主机目录:/容器目录 # 这是直接将两个目录进行映射 目录都以/开头
    # -v /容器目录 # 这是匿名挂载
    # -v 挂载名称:/容器目录 # 这是具名挂载 挂载名称不以/开头
    
    
    # 查看卷信息 docker volume 
    [root@localhost docker]# docker volume --help 
    
    Usage:  docker volume COMMAND
    
    Manage volumes
    
    Commands:
      create      Create a volume
      inspect     Display detailed information on one or more volumes
      ls          List volumes
      prune       Remove all unused local volumes
      rm          Remove one or more volumes
    
    Run 'docker volume COMMAND --help' for more information on a command.
    [root@localhost docker]# 
    [root@localhost docker]# 
    [root@localhost docker]# 
    [root@localhost docker]# docker volume ls # 目前不存在卷
    DRIVER    VOLUME NAME
    [root@localhost docker]# 
    
    # 匿名挂载
    [root@localhost docker]# 
    [root@localhost docker]# docker run -P -d -v /etc/nginx --name nginx01 nginx # 匿名挂载
    Unable to find image 'nginx:latest' locally
    latest: Pulling from library/nginx
    f7ec5a41d630: Already exists 
    aa1efa14b3bf: Pull complete 
    b78b95af9b17: Pull complete 
    c7d6bca2b8dc: Pull complete 
    cf16cd8e71e0: Pull complete 
    0241c68333ef: Pull complete 
    Digest: sha256:75a55d33ecc73c2a242450a9f1cc858499d468f077ea942867e662c247b5e412
    Status: Downloaded newer image for nginx:latest
    3d33b05202eeee3f3e60a68f7c9f039ea77dc4981cbf8557b8ec03a9ffbbc934
    [root@localhost docker]# docker ps
    CONTAINER ID   IMAGE       COMMAND                  CREATED          STATUS          PORTS                                                  NAMES
    3d33b05202ee   nginx       "/docker-entrypoint.…"   28 seconds ago   Up 26 seconds   80/tcp                                                 nginx01
    [root@localhost docker]# 
    [root@localhost docker]# docker volume ls # 查看卷信息
    DRIVER    VOLUME NAME
    local     1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3 # 匿名
    [root@localhost docker]# 
    [root@localhost docker]# ls /var/lib/docker/volumes/ # 查看目录中的卷信息
    1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3  metadata.db
    backingFsBlockDev
    [root@localhost docker]# 
    [root@localhost docker]# 
    [root@localhost docker]# docker volume inspect 1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3 # 查看挂载的详细信息
    [
        { 
            "CreatedAt": "2021-05-07T19:19:29+08:00",
            "Driver": "local",
            "Labels": null,
            "Mountpoint": "/var/lib/docker/volumes/1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3/_data", # 宿主机的目录
            "Name": "1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3",
            "Options": null,
            "Scope": "local"
        }
    ]
    [root@localhost docker]# 
    
    # 具名挂载（常用）
    [root@localhost docker]# 
    [root@localhost docker]# docker run -P -d -v nginx-Juming:/etc/nginx --name nginx02 nginx
    6f4fcf67b2fb40ab2cb81685dd4de7ac2cef38f6c2599e1eec719a79797c2538
    [root@localhost docker]# 
    [root@localhost docker]# docker volume ls
    DRIVER    VOLUME NAME
    local     1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3
    local     nginx-Juming  # 具名
    [root@localhost docker]# 
    [root@localhost docker]# ls /var/lib/docker/volumes/
    1f8593b8dd6b2c78764a5710d037156795a644d0f9460e40d4300b0fbdbc04b3  metadata.db
    backingFsBlockDev                                                 nginx-Juming # 具名
    [root@localhost docker]# 
    [root@localhost docker]# docker volume inspect nginx-Juming # 查看挂载的详细信息
    [
        { 
            "CreatedAt": "2021-05-07T19:27:01+08:00",
            "Driver": "local",
            "Labels": null,
            "Mountpoint": "/var/lib/docker/volumes/nginx-Juming/_data", # 宿主机的目录 可以在这里修改配置文件
            "Name": "nginx-Juming",
            "Options": null,
            "Scope": "local"
        }
    ]
    [root@localhost docker]#

#### 权限控制 ####

# 数据卷权限控制 -v nginx-Juming:/etc/nginx:ro
    [root@localhost docker]# docker run -P -d -v nginx-Juming:/etc/nginx:ro --name nginx02 nginx
    
    # ro: read only 只读。只能在容器外部改变文件，不能在容器内部改变文件
    # rw: read write 读写。默认权限。容器内外都能改变文件。

#### 方式二：使用DockerFile ####

之前我们使用commit构建过镜像。

初识Dockerfile。先体验一下。

Dockerfile就是用来构建docker镜像的构建文件！Dockerfile就是一段命令脚本，通过这个脚本可以生成镜像！镜像是一层一层的，脚本是一个一个命令，可以理解成每个命令就是一层镜像。

[root@localhost ~]# mkdir docker-build-test
    [root@localhost ~]# cd docker-build-test/
    [root@localhost docker-build-test]# 
    
    # 1.生成dockerfile
    [root@localhost docker-build-test]# vim DockerFile #名字可以自定义 建议用dockerfile
    # dockerfile中的内容每一行是一条命令。 每一条命令有指令（大写）和参数组成。每个命令就是一层镜像。
    [root@localhost docker-build-test]# cat DockerFile
    FROM centos    # 基于centos镜像为基础
    
    VOLUME ["volume01","volume02"]   # 自动挂载的数据卷目录
    
    CMD echo "----end----"
    
    CMD /bin/bash
    [root@localhost docker-build-test]#
    [root@localhost docker-build-test]# docker build --help
    
    Usage:  docker build [OPTIONS] PATH | URL | -
    
    Build an image from a Dockerfile
    
    Options:
          --add-host list           Add a custom host-to-IP mapping (host:ip)
          --build-arg list          Set build-time variables
          --cache-from strings      Images to consider as cache sources
          --cgroup-parent string    Optional parent cgroup for the container
          --compress                Compress the build context using gzip
          --cpu-period int          Limit the CPU CFS (Completely Fair Scheduler) period
          --cpu-quota int           Limit the CPU CFS (Completely Fair Scheduler) quota
      -c, --cpu-shares int          CPU shares (relative weight)
          --cpuset-cpus string      CPUs in which to allow execution (0-3, 0,1)
          --cpuset-mems string      MEMs in which to allow execution (0-3, 0,1)
          --disable-content-trust   Skip image verification (default true)
      -f, --file string             Name of the Dockerfile (Default is 'PATH/Dockerfile')
          --force-rm                Always remove intermediate containers
          --iidfile string          Write the image ID to the file
          --isolation string        Container isolation technology
          --label list              Set metadata for an image
      -m, --memory bytes            Memory limit
          --memory-swap bytes       Swap limit equal to memory plus swap: '-1' to
                                    enable unlimited swap
          --network string          Set the networking mode for the RUN instructions
                                    during build (default "default")
          --no-cache                Do not use cache when building the image
          --pull                    Always attempt to pull a newer version of the image
      -q, --quiet                   Suppress the build output and print image ID on success
          --rm                      Remove intermediate containers after a successful
                                    build (default true)
          --security-opt strings    Security options
          --shm-size bytes          Size of /dev/shm
      -t, --tag list                Name and optionally a tag in the 'name:tag' format
          --target string           Set the target build stage to build.
          --ulimit ulimit           Ulimit options (default [])
    [root@localhost docker-build-test]# 
    
    # 2.通过dockerfile构建镜像
    [root@localhost docker-build-test]# docker build -f /root/docker-build-test/DockerFile -t wuxl/centos:1.0 . 
    Sending build context to Docker daemon  2.048kB
    Step 1/4 : FROM centos
     ---> 300e315adb2f
    Step 2/4 : VOLUME ["volume01","volume02"]
     ---> Running in 46e3da7ae117
    Removing intermediate container 46e3da7ae117
     ---> 77b04bfac2fa
    Step 3/4 : CMD echo "----end----"
     ---> Running in dd2b6ddfed0b
    Removing intermediate container dd2b6ddfed0b
     ---> 8512e84141d6
    Step 4/4 : CMD /bin/bash
     ---> Running in eab90b2dd126
    Removing intermediate container eab90b2dd126
     ---> d60645df454b
    Successfully built d60645df454b
    Successfully tagged wuxl/centos:1.0
    [root@localhost docker-build-test]# 
    
    # 3.查看镜像
    [root@localhost docker-build-test]# docker images
    REPOSITORY    TAG       IMAGE ID       CREATED              SIZE
    wuxl/centos   1.0       d60645df454b   About a minute ago   209MB  # 构建的镜像
    tomcat        2.0       c01bd59511a6   7 days ago           672MB
    tomcat        latest    c0e850d7b9bb   2 weeks ago          667MB
    mysql         5.7       87eca374c0ed   2 weeks ago          447MB
    nginx         latest    62d49f9bab67   3 weeks ago          133MB
    centos        latest    300e315adb2f   5 months ago         209MB
    [root@localhost docker-build-test]# 
    
    # 4.运行镜像 这里需要注意，如果使用的是容器名称启动，必须加tag: wuxl/centos:1.0 
    [root@localhost docker-build-test]# docker run -it d60645df454b /bin/bash # 运行
    [root@b8d89421ecfd /]# 
    [root@b8d89421ecfd /]# ls
    bin  etc   lib    lost+found  mnt  proc  run   srv  tmp  var       volume02 # 目录
    dev  home  lib64  media       opt  root  sbin  sys  usr  volume01 # 目录
    [root@b8d89421ecfd /]#
    
    [root@localhost ~]# docker ps 
    CONTAINER ID   IMAGE          COMMAND                  CREATED              STATUS              PORTS                                                  NAMES
    b8d89421ecfd   d60645df454b   "/bin/bash"              About a minute ago   Up About a minute                                                          funny_banach
    
    # 查看容器的挂载情况（匿名挂载）
    [root@localhost ~]# docker inspect b8d89421ecfd
            "Mounts": [
                { 
                    "Type": "volume",
                    "Name": "2c728e3c84280bead80b4c39fd016dc87c385e377cea0fc12c4ced893eb7673b",
                    "Source": "/var/lib/docker/volumes/2c728e3c84280bead80b4c39fd016dc87c385e377cea0fc12c4ced893eb7673b/_data", # 宿主机目录
                    "Destination": "volume02", # 容器目录
                    "Driver": "local",
                    "Mode": "",
                    "RW": true,
                    "Propagation": ""
                },
                { 
                    "Type": "volume",
                    "Name": "1d8c109f6254daada08d5646529b630e8ff4cc9e099c7cb4a5674f9446e05ce1",
                    "Source": "/var/lib/docker/volumes/1d8c109f6254daada08d5646529b630e8ff4cc9e099c7cb4a5674f9446e05ce1/_data", # 宿主机目录
                    "Destination": "volume01", # 容器目录
                    "Driver": "local",
                    "Mode": "",
                    "RW": true,
                    "Propagation": ""
                }
            ],

这种方式使用的十分多，因为我们通常会构建自己的镜像。

假设构建镜像的时候没有挂载数据卷，要手动挂载镜像 -v 卷名:/容器内目录。

#### 数据卷容器 ####

两个容器相互同步数据。比如多个mysql容器同步数据。

![image-20210507121755944][]

# 使用上面我们通过dockerfile构建的镜像，启动三个容器 测试
    
    # 1.启动第一个容器（作为父容器或数据卷容器）
    [root@localhost ~]# docker ps 
    CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
    [root@localhost ~]# docker images
    REPOSITORY    TAG       IMAGE ID       CREATED          SIZE
    wuxl/centos   1.0       d60645df454b   39 minutes ago   209MB
    tomcat        2.0       c01bd59511a6   7 days ago       672MB
    tomcat        latest    c0e850d7b9bb   2 weeks ago      667MB
    mysql         5.7       87eca374c0ed   2 weeks ago      447MB
    nginx         latest    62d49f9bab67   3 weeks ago      133MB
    centos        latest    300e315adb2f   5 months ago     209MB
    [root@localhost ~]# 
    [root@localhost ~]# docker run -it --name wuxlcentos01 wuxl/centos:1.0
    [root@81d68891cee7 /]# ls -l
    total 0
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 bin -> usr/bin
    drwxr-xr-x.   5 root root 360 May  7 12:38 dev
    drwxr-xr-x.   1 root root  66 May  7 12:38 etc
    drwxr-xr-x.   2 root root   6 Nov  3  2020 home
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 lib -> usr/lib
    lrwxrwxrwx.   1 root root   9 Nov  3  2020 lib64 -> usr/lib64
    drwx------.   2 root root   6 Dec  4 17:37 lost+found
    drwxr-xr-x.   2 root root   6 Nov  3  2020 media
    drwxr-xr-x.   2 root root   6 Nov  3  2020 mnt
    drwxr-xr-x.   2 root root   6 Nov  3  2020 opt
    dr-xr-xr-x. 123 root root   0 May  7 12:38 proc
    dr-xr-x---.   2 root root 162 Dec  4 17:37 root
    drwxr-xr-x.  11 root root 163 Dec  4 17:37 run
    lrwxrwxrwx.   1 root root   8 Nov  3  2020 sbin -> usr/sbin
    drwxr-xr-x.   2 root root   6 Nov  3  2020 srv
    dr-xr-xr-x.  13 root root   0 May  7 09:13 sys
    drwxrwxrwt.   7 root root 145 Dec  4 17:37 tmp
    drwxr-xr-x.  12 root root 144 Dec  4 17:37 usr
    drwxr-xr-x.  20 root root 262 Dec  4 17:37 var
    drwxr-xr-x.   2 root root   6 May  7 12:38 volume01 # 数据卷01
    drwxr-xr-x.   2 root root   6 May  7 12:38 volume02 # 数据卷02
    [root@81d68891cee7 /]# 
    [root@81d68891cee7 /]# cd volume01
    [root@81d68891cee7 volume01]# touch centos01.java # 在数据卷01中创建一个文件
    [root@81d68891cee7 volume01]# ls
    centos01.java
    [root@81d68891cee7 volume01]# 
    
    
    # 启动第二个容器 继承wuxlcentos01容器的数据卷： --volumes-from wuxlcentos01 
    [root@localhost ~]# 
    [root@localhost ~]# docker run -it --volumes-from wuxlcentos01 --name wuxlcentos02 wuxl/centos:1.0
    [root@be78dfb1ac82 /]# ls -l
    total 0
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 bin -> usr/bin
    drwxr-xr-x.   5 root root 360 May  7 12:43 dev
    drwxr-xr-x.   1 root root  66 May  7 12:43 etc
    drwxr-xr-x.   2 root root   6 Nov  3  2020 home
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 lib -> usr/lib
    lrwxrwxrwx.   1 root root   9 Nov  3  2020 lib64 -> usr/lib64
    drwx------.   2 root root   6 Dec  4 17:37 lost+found
    drwxr-xr-x.   2 root root   6 Nov  3  2020 media
    drwxr-xr-x.   2 root root   6 Nov  3  2020 mnt
    drwxr-xr-x.   2 root root   6 Nov  3  2020 opt
    dr-xr-xr-x. 125 root root   0 May  7 12:43 proc
    dr-xr-x---.   2 root root 162 Dec  4 17:37 root
    drwxr-xr-x.  11 root root 163 Dec  4 17:37 run
    lrwxrwxrwx.   1 root root   8 Nov  3  2020 sbin -> usr/sbin
    drwxr-xr-x.   2 root root   6 Nov  3  2020 srv
    dr-xr-xr-x.  13 root root   0 May  7 09:13 sys
    drwxrwxrwt.   7 root root 145 Dec  4 17:37 tmp
    drwxr-xr-x.  12 root root 144 Dec  4 17:37 usr
    drwxr-xr-x.  20 root root 262 Dec  4 17:37 var
    drwxr-xr-x.   2 root root  27 May  7 12:39 volume01
    drwxr-xr-x.   2 root root   6 May  7 12:38 volume02
    [root@be78dfb1ac82 /]# ls /volume01/ # wuxlcentos01创建的数据
    centos01.java
    [root@be78dfb1ac82 /]# touch /volume01/centos02.java # wuxlcentos02也创建文件
    [root@be78dfb1ac82 /]# 
    [root@be78dfb1ac82 /]# ls /volume01/
    centos01.java  centos02.java
    [root@be78dfb1ac82 /]# 
    
    # 启动第三个容器 也继承wuxlcentos01容器的数据卷： --volumes-from wuxlcentos01 
    [root@localhost ~]# docker run -it --volumes-from wuxlcentos01 --name wuxlcentos03 wuxl/centos:1.0
    [root@f6c6b2d2c8e3 /]# ls -l
    total 0
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 bin -> usr/bin
    drwxr-xr-x.   5 root root 360 May  7 12:46 dev
    drwxr-xr-x.   1 root root  66 May  7 12:46 etc
    drwxr-xr-x.   2 root root   6 Nov  3  2020 home
    lrwxrwxrwx.   1 root root   7 Nov  3  2020 lib -> usr/lib
    lrwxrwxrwx.   1 root root   9 Nov  3  2020 lib64 -> usr/lib64
    drwx------.   2 root root   6 Dec  4 17:37 lost+found
    drwxr-xr-x.   2 root root   6 Nov  3  2020 media
    drwxr-xr-x.   2 root root   6 Nov  3  2020 mnt
    drwxr-xr-x.   2 root root   6 Nov  3  2020 opt
    dr-xr-xr-x. 130 root root   0 May  7 12:46 proc
    dr-xr-x---.   2 root root 162 Dec  4 17:37 root
    drwxr-xr-x.  11 root root 163 Dec  4 17:37 run
    lrwxrwxrwx.   1 root root   8 Nov  3  2020 sbin -> usr/sbin
    drwxr-xr-x.   2 root root   6 Nov  3  2020 srv
    dr-xr-xr-x.  13 root root   0 May  7 09:13 sys
    drwxrwxrwt.   7 root root 145 Dec  4 17:37 tmp
    drwxr-xr-x.  12 root root 144 Dec  4 17:37 usr
    drwxr-xr-x.  20 root root 262 Dec  4 17:37 var
    drwxr-xr-x.   2 root root  48 May  7 12:44 volume01  # 继承的数据卷
    drwxr-xr-x.   2 root root   6 May  7 12:38 volume02  # 继承的数据卷
    [root@f6c6b2d2c8e3 /]# ls /volume01/
    centos01.java  centos02.java
    [root@f6c6b2d2c8e3 /]# touch /volume01/centos03.java 
    [root@f6c6b2d2c8e3 /]# 
    [root@f6c6b2d2c8e3 /]# ls /volume01/ 
    centos01.java  centos02.java  centos03.java
    [root@f6c6b2d2c8e3 /]#

即使docker rm wuxlcentos01后，wuxlcentos02和wuxlcentos03的数据依然存在。因为数据共享是一个双向拷贝的概率。

![image-20210507122314696][]

两个mysql容器的数据如何实现同步？

[root@localhost ~]# docker run -d -p 3306:3306 -v /etc/mysql/conf.d -v /var/lib/mysql --name mysql01 -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
    
    [root@localhost ~]# docker run -d -p 3306:3306 --volumes-from mysql01 --name mysql02 -e MYSQL_ROOT_PASSWORD=123456 mysql:5.7
    
    # mysql02容器启动时使用--volumes-from mysql01 ，就可以使得两个mysql容器的数据同步了。
    # mysql01是父容器（数据卷容器），mysql02是mysql01的子容器。

**结论**

容器之间的配置信息的传递（集群），数据卷容器的生命周期一直持续到没有任何容器使用为止。不会因为某个容器的关闭、删除导致数据的丢失。一旦父容器的数据通过-v持久化到了宿主机，这个数据就不会丢失。

上述知识实际操作基本够用。

[image-20210506173442098]: /images/20221021/23e48f6271104563a1b3a0a3dc934b61.png
[image-20210507121755944]: /images/20221021/99f300f02e544c8c8f5f0656b3d1149a.png
[image-20210507122314696]: /images/20221021/b144a522719247319e2fcfb9092b88fc.png