1八、docker的持久化存储和数据共享

时间 2019-11-09

标签 docker 持久存储数据共享栏目 Docker 繁體版

原文原文链接

18.1 Data Volume

Docker持久化数据方案

基于本地文件系统的Volume

能够在执行docker create或者docker run的时候，经过-v参数将主机的目录做为容器的数据卷。这部分功能即是基于本地文件系统的Volume管理。html

基于plugin的Volume

支持第三方的存储方案，好比NAS、AWS等。mysql

Data Volume 类型

受管理的data volume，由docker后台自动建立
绑定挂载的volume，具体挂载位置能够由用户指定

经过例子来查看

以MySQL为例，能够查看官方的Dockerfile，当中用到了Volume。nginx

# 查看volume
[root@docker ~]# docker volume ls
[root@docker ~]# 
# 建立一个MySQL的容器
[root@docker ~]# docker run -d --name mysql1 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql

# 查看MySQL容器跑起来以后的volume
[root@docker ~]# docker volume ls
DRIVER              VOLUME NAME
local               e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac
[root@docker ~]# 
# 查看这个volume的想象信息
[root@docker ~]# docker volume inspect e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac
[
    {
        "CreatedAt": "2018-06-07T09:13:24Z",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/volumes/e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac/_data",
        "Name": "e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac",
        "Options": null,
        "Scope": "local"
    }
]
[root@docker ~]#

能够看到，这个volume并不在容器当中，而是挂载到了宿主机的/var/lib/docker/volumes/e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac/_data目录下。git

再建立一个mysql2的容器：github

[root@docker ~]# docker run -d --name mysql2 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql

[root@docker ~]# docker volume ls
DRIVER              VOLUME NAME
local               a3c730f24ca254cabbd328b4c5a6e7fa1822d7e1b2e54c9ac9104839295e5225
local               e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac
[root@docker ~]# docker volume inspect a3c730f24ca254cabbd328b4c5a6e7fa1822d7e1b2e54c9ac9104839295e5225
[
    {
        "CreatedAt": "2018-06-07T09:22:18Z",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/volumes/a3c730f24ca254cabbd328b4c5a6e7fa1822d7e1b2e54c9ac9104839295e5225/_data",
        "Name": "a3c730f24ca254cabbd328b4c5a6e7fa1822d7e1b2e54c9ac9104839295e5225",
        "Options": null,
        "Scope": "local"
    }
]
[root@docker ~]#

删除这两个容器：web

[root@docker ~]# docker stop mysql1 mysql2
[root@docker ~]# docker rm mysql1 mysql2
[root@docker ~]# docker volume ls
DRIVER              VOLUME NAME
local               a3c730f24ca254cabbd328b4c5a6e7fa1822d7e1b2e54c9ac9104839295e5225
local               e3c54bb7b620d86524b6cebc4c28568a2a81a104871a5baf41e22c02bd8d7bac
[root@docker ~]#

能够发现，volume在容器删除以后也不会被删除，能够防止容器删除以后数据也不存在了的问题。可是volume的名字很是不友好，不方便咱们使用，可是咱们能够在建立或者启动容器的时候给volume设置别名来方便咱们使用。sql

给volume起别名

从新建立mysql1容器，在启动的时候给volume设置别名docker

[root@docker ~]# sudo docker run -d -v mysql:/var/lib/mysql --name mysql1 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql
[root@docker ~]# docker volume ls
DRIVER              VOLUME NAME
local               mysql
[root@docker ~]# docker volume inspect mysql
[
    {
        "CreatedAt": "2018-06-07T09:30:33Z",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/volumes/mysql/_data",
        "Name": "mysql",
        "Options": null,
        "Scope": "local"
    }
]
[root@docker ~]#

验证一下这个mysql的volume是否已经被使用：进入mysql1容器，建立一个数据库shell

[root@docker ~]# docker exec -it mysql1 /bin/bash
root@5aa496b309cc:/# mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.11 MySQL Community Server - GPL

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

mysql> create database docker;
Query OK, 1 row affected (0.07 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| docker             |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> \q
Bye
root@5aa496b309cc:/# exit
[root@docker ~]# 中止mysql1容器，并删除mysql1容器
[root@docker ~]# docker stop mysql1
[root@docker ~]# docker rm mysql1
[root@docker ~]# 建立一个新的mysql2的容器，急需使用mysql这个volume
[root@docker ~]# sudo docker run -d -v mysql:/var/lib/mysql --name mysql2 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql
[root@docker ~]# 进入mysql2查看是否存在以前的数据
[root@docker ~]# docker exec -it mysql2 /bin/bash
root@cf1cc3ad331e:/# mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.11 MySQL Community Server - GPL

Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| docker             |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> \q
Bye
root@cf1cc3ad331e:/# exit

能够发现，volume中的数据并不会由于容器的删除二消失，实现了数据持久化的目标。可是这种方式的volume须要在Dockerfile中使用VOLUME来预先指定容器中的数据存放路径。数据库

18.2 Bind Mounting

Bind Mounting跟上面的方式不同，能够动态的指定容器内文件存放路径和宿主机上的数据库卷目录。

构建一个docker-nginx的镜像：

# Dockerfile
[root@docker docker-nginx]# cat Dockerfile
# this same shows how we can extend/change an existing official image from Docker Hub

FROM nginx:latest
# highly recommend you always pin versions for anything beyond dev/learn

WORKDIR /usr/share/nginx/html
# change working directory to root of nginx webhost
# using WORKDIR is prefered to using 'RUN cd /some/path'

COPY index.html index.html

# I don't have to specify EXPOSE or CMD because they're in my FROM
[root@docker docker-nginx]# cat index.html
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello Docker! </h1>
</body>
</html>
[root@docker docker-nginx]# 构建镜像
[root@docker docker-nginx]# docker build -t staryjie/docker-nginx .
[root@docker docker-nginx]# 建立容器
[root@docker docker-nginx]# docker run -d -p 80:80 --name web staryjie/docker-nginx
[root@docker docker-nginx]# 本地访问
[root@docker docker-nginx]# curl 127.0.0.1
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello Docker! </h1>
</body>
</html>
[root@docker docker-nginx]#

可是index.html文件是没法更改的，若是要更改必需要从新构建镜像，这样很是不便。

[root@docker docker-nginx]# 强制删除web容器
[root@docker docker-nginx]# docker rm -f web
[root@docker docker-nginx]# 从新建立一个容器，指定宿主机上index.html的目录到容器中nginx的html目录
[root@docker docker-nginx]# docker exec -it web1 /bin/bash
root@18af473954f1:/usr/share/nginx/html# ls
Dockerfile  index.html
root@18af473954f1:/usr/share/nginx/html# touch test.txt
root@18af473954f1:/usr/share/nginx/html# exit
[root@docker docker-nginx]# ls
Dockerfile  index.html  test.txt
[root@docker docker-nginx]# curl 127.0.0.1
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello Docker! </h1>
</body>
</html>
[root@docker docker-nginx]# 修改index.html
[root@docker docker-nginx]# cat index.html
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello Docker! </h1>
  <h1>Hello, I have changed this file! </h1>
</body>
</html>
[root@docker docker-nginx]# curl 127.0.0.1
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello Docker! </h1>
  <h1>Hello, I have changed this file! </h1>
</body>
</html>
[root@docker docker-nginx]#

采用Bind Mounting的方式实现volume的话，容器内外的数据是同步的，只须要修改一个地方，容器内或者容器外都会同步修改，很是的方便快捷。

采用Bind Mounting的方式，将docker做为开发环境可使咱们的开发环境和生产环境保持一致，这也是实现DevOps的第一步。（不少开发使用的都是Windows的系统，可是服务器通常都是Linux的，没法保持环境的一致性，影响开发效率。）

利用docker搭建一个与生产环境统一的开发环境