Docker持久化存储

时间 2020-06-23

标签 docker 持久存储栏目 Docker 繁體版

原文原文链接

　　Docker的镜像是只读的，可是容器是可写的，咱们能够将数据写入到容器，不过一旦容器删除数据将会丢失，那么有什么办法能将数据进行持久化存储呢？html

1、Data Volume

在执行docker run 时，经过-v参数将主机目录做为容器的数据卷，这就是基于本地文件系统Volumn管理。node

一、Volume类型

受管理的Volume，由docker后台自动建立
绑定挂载的Volume，具体挂载位置由用户指定

二、docker后台自动建立

以mysql镜像为例说明，进入到https://hub.docker.com/_/mysql查看详情。mysql

启动docker服务

[root@docker-node1 ~]# systemctl start docker

拉取mysql镜像

[root@docker-node1 ~]# docker pull mysql
Using default tag: latest latest: Pulling from library/mysql 619014d83c02: Pulling fs layer 9ced578c3a5f: Pulling fs layer

注意：若是出现Get https://registry-1.docker.io/v2/library/mysql/manifests/latest: dial tcp: lookup registry-1.docker.io on 8.8.8.8:53: read udp 192.168.0.109:41429->8.8.8.8:53: i/o timeout这种问题，能够尝试修改/etc/resolv.conf文件，加入nameserver 8.8.4.4linux

[root@docker-node1 ~]# cat /etc/resolv.conf # Generated by NetworkManager
nameserver 8.8.8.8 nameserver 8.8.4.4

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运行mysql镜像

[root@docker-node1 ~]# docker run -d --name mysql1 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql
9dd537e48f16fd924f19f95aa38d15e08bdfa254d65ee66f1e19331ed6e79ce3 [root@docker-node1 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 9dd537e48f16 mysql "docker-entrypoint.s…"   20 seconds ago      Up 11 seconds       3306/tcp, 33060/tcp   mysql1

这样就启动了一个mysql的容器mysql1，可是显然咱们并无指定数据库中表指定放到什么地方，那么它给咱们自动放到什么地方了呢？nginx

咱们能够看看mysql的Dockerfile：git

FROM debian:stretch-slim # add our user and group first to make sure their IDs get assigned consistently, regardless of whatever dependencies get added
RUN groupadd -r mysql && useradd -r -g mysql mysql RUN apt-get update && apt-get install -y --no-install-recommends gnupg dirmngr && rm -rf /var/lib/apt/lists/*

# add gosu for easy step-down from root
ENV GOSU_VERSION 1.7 RUN set -x \ && apt-get update && apt-get install -y --no-install-recommends ca-certificates wget && rm -rf /var/lib/apt/lists/* \ && wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture)" \ && wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$(dpkg --print-architecture).asc" \ && export GNUPGHOME="$(mktemp -d)" \ && gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 \ && gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu \ && gpgconf --kill all \ && rm -rf "$GNUPGHOME" /usr/local/bin/gosu.asc \ && chmod +x /usr/local/bin/gosu \ && gosu nobody true \ && apt-get purge -y --auto-remove ca-certificates wget RUN mkdir /docker-entrypoint-initdb.d RUN apt-get update && apt-get install -y --no-install-recommends \ # for MYSQL_RANDOM_ROOT_PASSWORD
 pwgen \ # for mysql_ssl_rsa_setup
 openssl \ # FATAL ERROR: please install the following Perl modules before executing /usr/local/mysql/scripts/mysql_install_db: # File::Basename # File::Copy # Sys::Hostname # Data::Dumper
 perl \ && rm -rf /var/lib/apt/lists/* RUN set -ex; \ # gpg: key 5072E1F5: public key "MySQL Release Engineering <mysql-build@oss.oracle.com>" imported
    key='A4A9406876FCBD3C456770C88C718D3B5072E1F5'; \ export GNUPGHOME="$(mktemp -d)"; \ gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \ gpg --batch --export "$key" > /etc/apt/trusted.gpg.d/mysql.gpg; \ gpgconf --kill all; \ rm -rf "$GNUPGHOME"; \ apt-key list > /dev/null ENV MYSQL_MAJOR 8.0 ENV MYSQL_VERSION 8.0.19-1debian9 RUN echo "deb http://repo.mysql.com/apt/debian/ stretch mysql-${MYSQL_MAJOR}" > /etc/apt/sources.list.d/mysql.list # the "/var/lib/mysql" stuff here is because the mysql-server postinst doesn't have an explicit way to disable the mysql_install_db codepath besides having a database already "configured" (ie, stuff in /var/lib/mysql/mysql) # also, we set debconf keys to make APT a little quieter
RUN { \ echo mysql-community-server mysql-community-server/data-dir select ''; \ echo mysql-community-server mysql-community-server/root-pass password ''; \ echo mysql-community-server mysql-community-server/re-root-pass password ''; \ echo mysql-community-server mysql-community-server/remove-test-db select false; \ } | debconf-set-selections \ && apt-get update && apt-get install -y mysql-community-client="${MYSQL_VERSION}" mysql-community-server-core="${MYSQL_VERSION}" && rm -rf /var/lib/apt/lists/* \ && rm -rf /var/lib/mysql && mkdir -p /var/lib/mysql /var/run/mysqld \ && chown -R mysql:mysql /var/lib/mysql /var/run/mysqld \ # ensure that /var/run/mysqld (used for socket and lock files) is writable regardless of the UID our mysqld instance ends up having at runtime
    && chmod 777 /var/run/mysqld VOLUME /var/lib/mysql  #持久化存储 # Config files
COPY config/ /etc/mysql/ COPY docker-entrypoint.sh /usr/local/bin/ RUN ln -s usr/local/bin/docker-entrypoint.sh /entrypoint.sh # backwards compat
ENTRYPOINT ["docker-entrypoint.sh"] EXPOSE 3306 33060 CMD ["mysqld"]

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实际上已经帮咱们持久化存储到主机的/var/lib/mysql目录中了。github

另外能够看到主机上有一条volume的记录：web

[root@docker-node1 ~]# docker volume ls
DRIVER VOLUME NAME local 5c4fbbc613e046baf9e148a301ef94ef09e4fc57312edd907885336e9ecd5bc1

能够看看这个存储卷记录的具体信息：sql

[root@docker-node1 ~]# docker volume inspect 5c4fbbc613e046baf9e148a301ef94ef09e4fc57312edd907885336e9ecd5bc1
[ { "CreatedAt": "2020-02-03T13:24:30+08:00", "Driver": "local", "Labels": null, "Mountpoint": "/var/lib/docker/volumes/5c4fbbc613e046baf9e148a301ef94ef09e4fc57312edd907885336e9ecd5bc1/_data", "Name": "5c4fbbc613e046baf9e148a301ef94ef09e4fc57312edd907885336e9ecd5bc1", "Options": null, "Scope": "local" } ]

持久化存储docker

若是咱们讲这个容器删掉，这个存储卷还存在吗？能够尝试一下：

[root@docker-node1 ~]# docker rm -f mysql1 #删掉mysql1容器
mysql1 [root@docker-node1 ~]# docker volume ls #存储卷仍旧存在
DRIVER VOLUME NAME local 5c4fbbc613e046baf9e148a301ef94ef09e4fc57312edd907885336e9ecd5bc1

能够看到虽然mysql的容器不在了，可是它的存储卷依旧存在。

三、用户指定挂载位置

上面你也许已经看到了一些须要自定义的地方：其一，volume name的名字太长了，须要本身指定；其二，volume持久化的目录须要本身指定。

容器重命名以及指定挂载位置

[root@docker-node1 ~]# docker run -d -v /home/mysql:/var/lib/mysql --name mysql1 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql
0e560c5c9caf902c0d9647ef1d7995803d9dfde8e0db2c529d97f913f943bdf5

上面经过-v参数指定mysql的挂载位置（主机文件位置：容器文件位置[Dockerfile中已经指定]），经过--name指定容器的名称，以下所示：

[root@docker-node1 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 0e560c5c9caf mysql "docker-entrypoint.s…"   9 seconds ago       Up 7 seconds        3306/tcp, 33060/tcp   mysql1

测试持久化

如今，能够先进入到这个容器中，对mysql的数据库中作一些改变，而后删掉容器：

（1）进入容器

[root@docker-node1 ~]# docker exec -it mysql1 /bin/sh

（2）进入mysql

# mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 8 Server version: 8.0.19 MySQL Community Server - GPL Copyright (c) 2000, 2020, 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.

（3）建立test数据库

mysql> create database test; Query OK, 1 row affected (0.36 sec) mysql> show databases; +--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| test               |
+--------------------+
5 rows in set (0.00 sec)

（4）删掉mysql1容器

[root@docker-node1 ~]# docker rm -f mysql1
mysql1

（5）新建mysql2容器

新建mysql2容器，而且指向mysql1容器的存储卷：

[root@docker-node1 ~]# docker run -d -v /home/mysql:/var/lib/mysql --name mysql2 -e MYSQL_ALLOW_EMPTY_PASSWORD=true mysql
9fc1aff1e798b0b6b4c01b26160877253c655f137a542734eb81b2b8984af66c

而后能够进入到mysql2容器中查看mysql中是否有mysql1容器建立的test数据库：

[root@docker-node1 ~]# docker exec -it mysql2 /bin/sh #进入mysql2容器 # mysql -uroot
Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 8 Server version: 8.0.19 MySQL Community Server - GPL Copyright (c) 2000, 2020, 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                |
| test               |
+--------------------+
5 rows in set (0.16 sec)

能够看到倒是存在test数据库，这样也就实现了volume持久化。

2、Bind Mounting

一、bing mounting和data volume的区别

data volume 须要在 Dockerfile文件中定义 volume，这种方式较多的是将容器映射到本地，实现容器与外部程序共享数据。
bind mounting 只须要 -v 指明容器外部文件夹和容器映射文件夹的对应关系，将本地的文件映射到容器内。

二、bind mounting的应用

在bindmounting-test文件夹中新建两个文件

[root@docker-node1 bindmounting-test]# ls
Dockerfile  index.html

编写Dockerfile文件

FROM nginx     #基础镜像
WORKDIR /usr/share/nginx/html  #工做目录，容器内的目录
COPY index.html .  #将本机当前目录下的index.html文件拷贝到上述工做目录下

编写index.html

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>hello</title>
</head>
<body>
  <h1>Hello Docker! </h1>
</body>
</html>

生成镜像

[root@docker-node1 bindmounting-test]# docker build -t docker-nginx .
Sending build context to Docker daemon  3.072kB Step 1/3 : FROM nginx ---> f68d6e55e065 Step 2/3 : WORKDIR /usr/share/nginx/html ---> Running in 3b784d71c4dc Removing intermediate container 3b784d71c4dc ---> 10cef7e9bbb9 Step 3/3 : COPY index.html . ---> f43b1a1b7bef Successfully built f43b1a1b7bef Successfully tagged docker-nginx:latest

运行docker-nginx镜像

[root@docker-node1 bindmounting-test]# docker run -d -p 80:80 --name web docker-nginx
22c28d4887d222785a3c60ca28c2fe79ff82ff9e630af0cdbb48232171732c90

上面经过-p进行了端口暴露，可经过外网访问：

　　可是难道每次修改index.html文件都须要从新生成镜像，而后运行吗？咱们能够经过bing mounting进行映射，若是本地文件变了，容器内的就会改变。这样就不会从新生成镜像了。

使用bind mounting

[root@docker-node1 bindmounting-test]# ls
Dockerfile index.html [root@docker-node1 bindmounting-test]# docker run -d -v $(pwd):/usr/share/nginx/html -p 80:80 --name web docker-nginx
f4661067be3fdead6c627bc00a054244b92207d42baebafdc37b8c8a8fe6f3cb

　　能够看到上面我将$(pwd)这个当前路劲的文件，也就是bindmounting-test文件夹中内容映射到容器/usr/share/nginx/html目录下，若是本地bindmounting-test文件夹下有文件更改了，容器中天然会变化。

　　例如，修改本地index.html文件中的内容：

[root@docker-node1 bindmounting-test]# vim index.html

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">

  <title>hello</title>

</head>

<body>
  <h1>Hello </h1>
</body>
</html>

此时，再刷新页面：

这样当在容器内或者容器外更改映射文件夹内的内容时两边都会改变，很利于开发者在linux进行应用的迭代更新部署。

3、总结

一、完成Data volume的步骤

Dockerfile中指定volume参数，如 VOLUME /var/lib/mysql
docker run -v /home/mysql:/var/lib/mysql

二、完成Bind Mounting的步骤

docker run -v /home/mysql:/var/lib/mysql

上面的映射关系都是主机：容器