docker深入1-docker的数据卷
docker深入1-docker的数据卷1
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参考：
http://docs.docker.com/userguide/dockervolumes/
针对数据的存储，有个data volume的概念。
使用参数： -v
在container中创建一个volume，或者类似目录映射的方式，挂载一个数据盘或者目录到docker的container中。
环境准备：
# yum install docker-io -y
# docker -v
Docker version 1.5.0, build a8a31ef/1.5.0
# service docker start
# useradd Jack && usermod -a -G docker Jack
# su Jack
$ docker pull centos
$ docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
centos 7 fd44297e2ddb 11 days ago 215.7 MB
centos centos7 fd44297e2ddb 11 days ago 215.7 MB
centos latest fd44297e2ddb 11 days ago 215.7 MB
一、简单的方式是：挂载一个数据目录到container中
$ docker run -d -it -v /home/datacenter:/datacenter --name datacenter centos
66f5e0e0e7042e371c092ff24117598055b7f65d4224f9738efbf13ba6273127
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
66f5e0e0e704 centos:7 "/bin/bash" 12 seconds ago Up 11 seconds datacenter
$ docker attach test01
# ll /
total 60
lrwxrwxrwx. 1 root root 7 Apr 15 14:28 bin -> usr/bin
drwxr-xr-x. 2 root root 4096 May4 02:55 datacenter
drwxr-xr-x. 5 root root380 May4 02:51 dev
drwxr-xr-x.47 root root 4096 May4 02:51 etc
drwxr-xr-x. 2 root root 4096 Jun 102014 home
lrwxrwxrwx. 1 root root 7 Apr 15 14:28 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Apr 15 14:28 lib64 -> usr/lib64
drwx------. 2 root root 4096 Apr 15 14:26 lost+found
drwxr-xr-x. 2 root root 4096 Jun 102014 media
drwxr-xr-x. 2 root root 4096 Jun 102014 mnt
drwxr-xr-x. 2 root root 4096 Jun 102014 opt
dr-xr-xr-x. 235 root root 0 May4 02:51 proc
dr-xr-x---. 2 root root 4096 Apr 15 14:29 root
drwxr-xr-x.10 root root 4096 Apr 15 14:29 run
lrwxrwxrwx. 1 root root 8 Apr 15 14:28 sbin -> usr/sbin
drwxr-xr-x. 2 root root 4096 Jun 102014 srv
dr-xr-xr-x.13 root root 0 May4 02:51 sys
-rw-r--r--. 1 root root 11 May4 02:52 test01
-rw-r--r--. 1 root root 11 May4 02:52 test04
drwxrwxrwt. 7 root root 4096 May4 02:51 tmp
drwxr-xr-x.13 root root 4096 Apr 15 14:28 usr
drwxr-xr-x.19 root root 4096 Apr 15 14:29 var
# df -h
Filesystem SizeUsed Avail Use% Mounted on
/dev/mapper/docker-252:0-262241-66f5e0e0e7042e371c092ff24117598055b7f65d4224f9738efbf13ba62731279.8G254M9.0G 3% /
tmpfs 1.9G 01.9G 0% /dev
shm 64M 0 64M 0% /dev/shm
/dev/mapper/vg_svr20010-lv_root 50G9.3G 38G20% /etc/hosts
/dev/mapper/vg_svr20010-lv_home 405G 48G338G13% /datacenter
tmpfs 1.9G 01.9G 0% /proc/kcore
写入数据：
# echo "`date` aaa" >/datacenter/test01
# echo "`date` 123" >/datacenter/test02
# ls /datacenter/
test01test02
# cat /datacenter/test0*
Mon May4 02:57:19 UTC 2015 aaa
Mon May4 02:57:27 UTC 2015 123
# exit
exit
查看宿主机挂载目录的文件和内容：
$ ll /home/datacenter
total 8
-rw-r--r--. 1 root root 33 May4 10:57 test01
-rw-r--r--. 1 root root 33 May4 10:57 test02
$ cat /home/datacenter/test0*
Mon May4 02:57:19 UTC 2015 aaa
Mon May4 02:57:27 UTC 2015 123
$ docker stop datacenter
datacenter
$ docker rm datacenter
datacenter
二、复杂一点儿：创建一个data volume container，共享给其他container
如官网所示：
If you have some persistent data that you want to share between containers, or want to use from non-persistent containers, it's best to create a named Data Volume Container, and then to mount the data from it.
1）创建一个container，提供一个数据卷供其他container使用：
$ docker run -d -it -v /home/datacenter:/datacenter --name Data_Vol centos
7691eccc73f6e4e2e2c3d6816cf6ba6a80a5f98f5067d48db6e8bafb4e4db021
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
7691eccc73f6 centos:7 "/bin/bash" 7 seconds ago Up 5 seconds Data_Vol
再创建2个container，使用刚才创建的数据卷Data_Vol来存储数据。
在启动container时，用这个参数：--volumes-from Data_Vol，而不是之前提到的-v参数，来挂载数据卷。
2）创建一个container：app1 ，写入一点儿数据
$ docker run -d -it --volumes-from Data_Vol --name app1 centos
1474f622b7f04c98da98e320d10864538b50b0b053677bbda039c8fb657062c1
$ docker attach app1
# ll /
total 52
lrwxrwxrwx. 1 root root 7 Apr 15 14:28 bin -> usr/bin
drwxr-xr-x. 2 root root 4096 May4 02:56 datacenter
drwxr-xr-x. 5 root root380 May4 03:40 dev
drwxr-xr-x.47 root root 4096 May4 03:40 etc
drwxr-xr-x. 2 root root 4096 Jun 102014 home
lrwxrwxrwx. 1 root root 7 Apr 15 14:28 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Apr 15 14:28 lib64 -> usr/lib64
drwx------. 2 root root 4096 Apr 15 14:26 lost+found
drwxr-xr-x. 2 root root 4096 Jun 102014 media
drwxr-xr-x. 2 root root 4096 Jun 102014 mnt
drwxr-xr-x. 2 root root 4096 Jun 102014 opt
dr-xr-xr-x. 244 root root 0 May4 03:40 proc
dr-xr-x---. 2 root root 4096 Apr 15 14:29 root
drwxr-xr-x.10 root root 4096 Apr 15 14:29 run
lrwxrwxrwx. 1 root root 8 Apr 15 14:28 sbin -> usr/sbin
drwxr-xr-x. 2 root root 4096 Jun 102014 srv
dr-xr-xr-x.13 root root 0 May4 03:40 sys
drwxrwxrwt. 7 root root 4096 May4 03:40 tmp
drwxr-xr-x.13 root root 4096 Apr 15 14:28 usr
drwxr-xr-x.19 root root 4096 Apr 15 14:29 var
# ls /datacenter/
test01test02
# touch /datacenter/app1
# ls /datacenter/
app1test01test02
# echo "`date` hello app1" >/datacenter/app1
# cat /datacenter/app1
Mon May4 03:43:11 UTC 2015 hello app1
# exit
exit
2）再创建一个container：app2 ，写入一点儿数据
$ docker run -d -it --volumes-from Data_Vol --name app2 centos
c4d743681ec95d78b21a52d3a558b4cab40a9f7ba43e884e4686c57c313b6923
$ docker attach app2
# df -h
Filesystem SizeUsed Avail Use% Mounted on
/dev/mapper/docker-252:0-262241-c4d743681ec95d78b21a52d3a558b4cab40a9f7ba43e884e4686c57c313b69239.8G254M9.0G 3% /
tmpfs 1.9G 01.9G 0% /dev
shm 64M 0 64M 0% /dev/shm
/dev/mapper/vg_svr20010-lv_root 50G9.3G 38G20% /etc/hosts
/dev/mapper/vg_svr20010-lv_home 405G 48G338G13% /datacenter
tmpfs 1.9G 01.9G 0% /proc/kcore
# ls /datacenter/
app1test01test02
# cat /datacenter/app1
Mon May4 03:43:11 UTC 2015 hello app1
# echo "`date` this is app2" >/datacenter/app2
# exit
exit
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c4d743681ec9 centos:7 "/bin/bash" 6 minutes ago Exited (0) 6 seconds ago app2
1474f622b7f0 centos:7 "/bin/bash" 6 minutes ago Exited (130) About a minute ago app1
7691eccc73f6 centos:7 "/bin/bash" 7 minutes ago Up 7 minutes Data_Vol
$
3）我们停止Data_Vol这个容器，再试试写入数据
$ docker stop Data_Vol
Data_Vol
$
$ docker start app1
app1
$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c4d743681ec9 centos:7 "/bin/bash" 7 minutes ago Exited (0) About a minute ago app2
1474f622b7f0 centos:7 "/bin/bash" 8 minutes ago Up 7 seconds app1
7691eccc73f6 centos:7 "/bin/bash" 8 minutes ago Exited (137) 16 seconds ago Data_Vol
$ docker attach app1
# ls /datacenter/
app1app2test01test02
# echo "`date` app1 is back here" >>/datacenter/app1
# cat /datacenter/app1
Mon May4 03:43:11 UTC 2015 hello app1
Mon May4 03:48:53 UTC 2015 app1 is back here
# exit
exit
看起来，，这个用来持久化的Data_Vol不用启动，，其他的container用--volumes-from Data_Vol来挂载数据卷，也是可以正常使用的。
4）回到宿主机了，我们看下数据
$ ls /home/datacenter/
app1app2test01test02
看起来，文件都在这里呢，再看下数据：
$ cat /home/datacenter/app1
Mon May4 03:43:11 UTC 2015 hello app1
Mon May4 03:48:53 UTC 2015 app1 is back here
$ cat /home/datacenter/app2
Mon May4 03:46:37 UTC 2015 this is app2
看，符合预期。
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