Docker 可以说是自OpenStack后现在最火的容器技术，可以方便快捷的完成应用程序的打包和部署，本例运行在Ubuntu 14.04 (LTS)虚拟机上，每个运行的容器实例(如nova instances)之间是相互隔离的。 Docker images 是容器技术的基础，Docker有两种方式来更新和构建镜像:
- We can update a container created from an image and commit the results to an image by
docker commitcommand. - We can use a
Dockerfileto specify instructions to create an image.
让我们看看如何通过 Dockerfile 构建一个包含mariadb application 的Docker 镜像。
1. Install Docker
$ wget -qO- https://get.docker.com/ | sh
详细的安装步骤可以参考官方安装文档.
2. Download Ubuntu base image from Docker Hub
$ docker run ubuntu:14.04
Unable to find image 'ubuntu:14.04' locally
14.04: Pulling from ubuntu
428b411c28f0: Already exists
435050075b3f: Already exists
9fd3c8c9af32: Already exists
6d4946999d4f: Already exists
Digest: sha256:59662c823007a7a6fbc411910b472cf4ed862e8f74603267ddfe20d5af4f9d79
Status: Downloaded newer image for ubuntu:14.04
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
ubuntu latest 6d4946999d4f 2 weeks ago 188.3 MB
ubuntu 14.04 6d4946999d4f 2 weeks ago 188.3 MB
This command downloads the specified image and runs it in a container.
3. 创建Dockerfile
创建一个工作目录，如 dockerfiles ，然后创建一个名为 Dockerfile 的文本文件，编写内容如下：
# Sets the base image
FROM ubuntu:14.04
# Set the Author of the generated image
MAINTAINER wenchma <wenchma@gmail.com>
# Set the environment variables inside container
ENV MYSQL_ROOT_PASSWORD mypassword
ENV MYSQL_DATADIR /var/lib/mysql
# Set the MariaDB public key and repository
RUN apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xcbcb082a1bb943db
RUN echo 'deb http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.0/ubuntu trusty main' | tee /etc/apt/sources.list.d/mariadb.list
# update the MariaDB repo and install the packages
RUN apt-get update
RUN apt-get install -y -q mariadb-server mariadb-client
# set MariaDB data dir and log dir
RUN mkdir -p /var/lib/mysql && mkdir -p /var/log/mysql && chown mysql:mysql /var/log/mysql
# set the port in container to expose to host
EXPOSE 3306
4. 构建Docker MariaDB 镜像
$ docker build -t wenchma/ubuntu:mariadb .
Sending build context to Docker daemon 20.15 MB
Sending build context to Docker daemon
Step 0 : FROM ubuntu:14.04
---> 6d4946999d4f
Step 1 : MAINTAINER wenchma <wenchma@gmail.com>
---> Using cache
---> ce6687ba3415
Step 2 : ENV MYSQL_ROOT_PASSWORD mypassword
---> Using cache
---> 711c5d00c490
Step 3 : ENV MYSQL_DATADIR /var/lib/mysql
---> Using cache
---> 0aca6d1fa456
Step 4 : RUN apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 0xcbcb082a1bb943db
---> Using cache
---> f14b6903246f
Step 5 : RUN echo 'deb http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.0/ubuntu trusty main' | tee /etc/apt/sources.list.d/mariadb.list
---> Running in 8caa96d12fa1
deb http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.0/ubuntu trusty main
---> 12231367c510
Removing intermediate container 8caa96d12fa1
Step 6 : RUN apt-get update
---> Running in cbd89fde87d3
Get:1 http://sfo1.mirrors.digitalocean.com trusty InRelease [2488 B]
Ign http://archive.ubuntu.com trusty InRelease
Ign http://archive.ubuntu.com trusty-updates InRelease
......
Reading package lists...
---> 19bd40f631e4
Removing intermediate container cbd89fde87d3
Step 7 : RUN apt-get install -y -q mariadb-server mariadb-client
---> Running in 9376a559e85e
Reading package lists...
Building dependency tree...
Reading state information...
The following extra packages will be installed:
libaio1 libdbd-mysql-perl libdbi-perl libhtml-template-perl
libmariadbclient18 libmysqlclient18 libreadline5 mariadb-client-10.0
mariadb-client-core-10.0 mariadb-common mariadb-server-10.0
mariadb-server-core-10.0 mysql-common psmisc
Suggested packages:
libclone-perl libmldbm-perl libnet-daemon-perl libplrpc-perl
libsql-statement-perl libipc-sharedcache-perl libterm-readkey-perl tinyca
mailx mariadb-test
The following NEW packages will be installed:
libaio1 libdbd-mysql-perl libdbi-perl libhtml-template-perl
libmariadbclient18 libmysqlclient18 libreadline5 mariadb-client
mariadb-client-10.0 mariadb-client-core-10.0 mariadb-common mariadb-server
mariadb-server-10.0 mariadb-server-core-10.0 mysql-common psmisc
0 upgraded, 16 newly installed, 0 to remove and 11 not upgraded.
Need to get 13.9 MB of archives.
After this operation, 137 MB of additional disk space will be used.
Get:1 http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.0/ubuntu/ trusty/main mysql-common all 10.0.20+maria-1~trusty [8388 B]
......
Get:16 http://archive.ubuntu.com/ubuntu/ trusty/main libhtml-template-perl all 2.95-1 [65.5 kB]
Preparing to unpack .../psmisc_22.20-1ubuntu2_amd64.deb ...
Unpacking psmisc (22.20-1ubuntu2) ...
Selecting previously unselected package mariadb-server-core-10.0.
......
Configuring mariadb-server-10.0
-------------------------------
While not mandatory, it is highly recommended that you set a password for the
MariaDB administrative "root" user.
If this field is left blank, the password will not be changed.
New password for the MariaDB "root" user:
Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
Use of uninitialized value $val in substitution (s///) at /usr/share/perl5/Debconf/Format/822.pm line 83, <GEN6> line 1.
Use of uninitialized value $val in concatenation (.) or string at /usr/share/perl5/Debconf/Format/822.pm line 84, <GEN6> line 1.
Unpacking mariadb-server-10.0 (10.0.20+maria-1~trusty) ...
Selecting previously unselected package libhtml-template-perl.
Preparing to unpack .../libhtml-template-perl_2.95-1_all.deb ...
......
Configuring mariadb-server-10.0
-------------------------------
While not mandatory, it is highly recommended that you set a password for the
MariaDB administrative "root" user.
If this field is left blank, the password will not be changed.
New password for the MariaDB "root" user:
Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111.
invoke-rc.d: policy-rc.d denied execution of stop.
invoke-rc.d: policy-rc.d denied execution of start.
Setting up mariadb-client (10.0.20+maria-1~trusty) ...
Processing triggers for ureadahead (0.100.0-16) ...
Setting up mariadb-server (10.0.20+maria-1~trusty) ...
Processing triggers for libc-bin (2.19-0ubuntu6.6) ...
---> 3367c0b221b9
Removing intermediate container 9376a559e85e
Step 8 : RUN mkdir -p /var/lib/mysql && mkdir -p /var/log/mysql && chown mysql:mysql /var/log/mysql
---> Running in af3cdc6b1a8b
---> 5715c0920490
Removing intermediate container af3cdc6b1a8b
Step 9 : EXPOSE 3306
---> Running in ecacf80ce76e
---> 6849bb03001e
Removing intermediate container ecacf80ce76e
Successfully built 6849bb03001e
5. 验证我们构建的镜像
列出镜像列表：
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
wenchma/ubuntu mariadb 6849bb03001e 9 seconds ago 463.5 MB
ubuntu 14.04 6d4946999d4f 2 weeks ago 188.3 MB
ubuntu latest 6d4946999d4f 2 weeks ago 188.3 MB
用我们新构建的镜像创建一个容器并测试一下MariaDB：
$ docker run -it wenchma/ubuntu:mariadb /bin/bash
root@d31eca25d0a9:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root@d31eca25d0a9:/# ls /var/lib/mysql/
aria_log.00000001 aria_log_control debian-10.0.flag ib_logfile0 ib_logfile1 ibdata1 mysql performance_schema
root@d31eca25d0a9:/# /etc/init.d/mysql status
* MariaDB is stopped.
root@d31eca25d0a9:/# /etc/init.d/mysql start
* Starting MariaDB database server mysqld [ OK ]
* Checking for corrupt, not cleanly closed and upgrade needing tables.
root@d31eca25d0a9:/# /etc/init.d/mysql status
* /usr/bin/mysqladmin Ver 9.1 Distrib 10.0.20-MariaDB, for debian-linux-gnu on x86_64
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Server version 10.0.20-MariaDB-1~trusty-log
Protocol version 10
Connection Localhost via UNIX socket
UNIX socket /var/run/mysqld/mysqld.sock
Uptime: 9 sec
Threads: 1 Questions: 705 Slow queries: 0 Opens: 167 Flush tables: 1 Open tables: 31 Queries per second avg: 78.333
root@d31eca25d0a9:/# mysql
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 45
Server version: 10.0.20-MariaDB-1~trusty-log mariadb.org binary distribution
Copyright (c) 2000, 2015, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
+--------------------+
3 rows in set (0.00 sec)
docker run 这种方式启动的container, 如果你退出后container也就关闭了.
docker start <container-id> # start your stopped container.
# list 所有状态的container
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
37c688837ad4 ubuntu:14.04 "/bin/bash" 41 minutes ago Exited (0) 32 seconds ago berserk_cori
f957fa8f119b ubuntu:14.04 "/usr/sbin/sshd -D" 42 minutes ago evil_thompson
35f84153ecbd ubuntu:14.04 "/usr/sbin/sshd-D" 42 minutes ago furious_darwin
0a86cb72698a wenchma/ubuntu:mariadb "/bin/bash" 58 minutes ago Exited (0) 44 minutes ago condescending_leakey
d31eca25d0a9 wenchma/ubuntu:mariadb "/bin/bash" 2 weeks ago Exited (0) 2 weeks ago grave_engelbart
503013aeaf75 f14b6903246f10fc59f83f42154f3854991dc2dd5bbf14e367555bcf42959c4c "/bin/sh -c 'add-apt 2 weeks ago Exited (127) 2 weeks ago focused_carson
$ docker start 37c688837ad4
37c688837ad4
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
37c688837ad4 ubuntu:14.04 "/bin/bash" 56 minutes ago Up 4 seconds berserk_cori
$ docker exec 37c688837ad4 ifconfig
eth0 Link encap:Ethernet HWaddr 02:42:ac:11:00:1a
inet addr:172.17.0.26 Bcast:0.0.0.0 Mask:255.255.0.0
inet6 addr: fe80::42:acff:fe11:1a/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:648 (648.0 B) TX bytes:738 (738.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
docker run 是启动一个container然后执行命令，docker exec 是在一个running container执行命令.
自此，我们的镜像就构建成功了，当然你也可以push 你的镜像到Docker Hub, 这里面有全世界开发者贡献的镜像。