介绍
卷是目录和文件，存在于一个或多个容器中，由docker挂载到容器，但不属于联合文件系统，因此能够绕过UnionFS提供一些用于持续存储或共享数据的特性。——将docker容器内的数据保存进宿主机的磁盘中。
卷的设计目的：数据持久化，独立于容器的生命周期，因此docker不会在容器删除时删除其挂载的数据卷。
作用
将容器中的数据备份到宿主机的磁盘中。
特点：
- 数据卷可在容器之间共享或重用数据；
- 卷中的更改可以直接实时生效；
- 数据卷中的更改不会包含在镜像的更新中；
- 数据卷的生命周期一直持续到没有容器使用它为止。
数据卷运用
如何运行一个带有容器数据卷存储功能的容器实例
docker run -it --privileged=true -v /宿主机绝对路径目录:/容器内目录 镜像名
[root@192 ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
192.168.12.130:5000/kdubuntu 1.2 9582a943a6b6 6 hours ago 116MB
kd/myubuntu 1.2 9582a943a6b6 6 hours ago 116MB
registry latest b8604a3fe854 17 months ago 26.2MB
ubuntu latest ba6acccedd29 17 months ago 72.8MB
redis 6.0.8 16ecd2772934 2 years ago 104MB
[root@192 ~]# docker run -it --privileged=true -v /tmp/host_data:/tmp/docker_data --name=u1 ubuntu
root@6f9775c9af9a:/# pwd
/
root@6f9775c9af9a:/# cd /tmp
root@6f9775c9af9a:/tmp# ll
total 0
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ./
drwxr-xr-x. 1 root root 17 Apr 8 14:33 ../
drwxr-xr-x. 2 root root 6 Apr 8 14:33 docker_data/
root@6f9775c9af9a:/tmp# cd docker_data/
root@6f9775c9af9a:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 6 Apr 8 14:33 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ../
root@6f9775c9af9a:/tmp/docker_data#
[root@192 tmp]# ll
total 147440
-rw-r--r--. 1 root root 75157504 Apr 5 07:59 abd.tar
-rw-r--r--. 1 root root 0 Apr 5 07:55 a.txt
drwx------. 2 kuangdi kuangdi 25 Apr 5 03:04 firefox
drwxr-xr-x. 2 root root 6 Apr 8 07:33 host_data
drwxr-xr-x. 2 root root 18 Apr 5 01:09 hsperfdata_root
[root@192 host_data]# ll
total 0
当前容器中，有/tmp/docker_data目录，按照之前分析，/tmp/docker_data目录与宿主机中的/tmp/host_data对应，那么在/tmp/docker_data目录下创建的文件在宿主机中的/tmp/host_data目录下也可以看见，反之亦然。
root@6f9775c9af9a:/tmp/docker_data# touch dockerin.txt
root@6f9775c9af9a:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 26 Apr 8 14:36 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
[root@192 host_data]# ll
total 0
-rw-r--r--. 1 root root 0 Apr 8 07:36 dockerin.txt
查看数据卷是否挂载成功
docker inspect 容器ID
[root@192 host_data]# docker inspect 6f9775c9af9a
[
{
"Id": "6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d",
"Created": "2023-04-08T14:33:26.684139466Z",
"Path": "bash",
"Args": [],
"State": {
"Status": "running",
"Running": true,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
"Dead": false,
"Pid": 3015,
"ExitCode": 0,
"Error": "",
"StartedAt": "2023-04-08T14:33:27.738661741Z",
"FinishedAt": "0001-01-01T00:00:00Z"
},
"Image": "sha256:ba6acccedd2923aee4c2acc6a23780b14ed4b8a5fa4e14e252a23b846df9b6c1",
"ResolvConfPath": "/var/lib/docker/containers/6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d/resolv.conf",
"HostnamePath": "/var/lib/docker/containers/6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d/hostname",
"HostsPath": "/var/lib/docker/containers/6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d/hosts",
"LogPath": "/var/lib/docker/containers/6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d/6f9775c9af9a16c58ff205801c42112a99d4a62c39b42f68a42470f30679926d-json.log",
"Name": "/u1",
"RestartCount": 0,
"Driver": "overlay2",
"Platform": "linux",
"MountLabel": "",
"ProcessLabel": "",
"AppArmorProfile": "",
"ExecIDs": null,
"HostConfig": {
"Binds": [
"/tmp/host_data:/tmp/docker_data"
],
"ContainerIDFile": "",
"LogConfig": {
"Type": "json-file",
"Config": {}
},
"NetworkMode": "default",
"PortBindings": {},
"RestartPolicy": {
"Name": "no",
"MaximumRetryCount": 0
},
"AutoRemove": false,
"VolumeDriver": "",
"VolumesFrom": null,
"ConsoleSize": [
38,
104
],
"CapAdd": null,
"CapDrop": null,
"CgroupnsMode": "host",
"Dns": [],
"DnsOptions": [],
"DnsSearch": [],
"ExtraHosts": null,
"GroupAdd": null,
"IpcMode": "private",
"Cgroup": "",
"Links": null,
"OomScoreAdj": 0,
"PidMode": "",
"Privileged": true,
"PublishAllPorts": false,
"ReadonlyRootfs": false,
"SecurityOpt": [
"label=disable"
],
"UTSMode": "",
"UsernsMode": "",
"ShmSize": 67108864,
"Runtime": "runc",
"Isolation": "",
"CpuShares": 0,
"Memory": 0,
"NanoCpus": 0,
"CgroupParent": "",
"BlkioWeight": 0,
"BlkioWeightDevice": [],
"BlkioDeviceReadBps": [],
"BlkioDeviceWriteBps": [],
"BlkioDeviceReadIOps": [],
"BlkioDeviceWriteIOps": [],
"CpuPeriod": 0,
"CpuQuota": 0,
"CpuRealtimePeriod": 0,
"CpuRealtimeRuntime": 0,
"CpusetCpus": "",
"CpusetMems": "",
"Devices": [],
"DeviceCgroupRules": null,
"DeviceRequests": null,
"MemoryReservation": 0,
"MemorySwap": 0,
"MemorySwappiness": null,
"OomKillDisable": false,
"PidsLimit": null,
"Ulimits": null,
"CpuCount": 0,
"CpuPercent": 0,
"IOMaximumIOps": 0,
"IOMaximumBandwidth": 0,
"MaskedPaths": null,
"ReadonlyPaths": null
},
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/99549b82dea04814af5b2a2c0cfa91b6a1e078f1a86335383fc0e650f43c8ae4-init/diff:/var/lib/docker/overlay2/e81934f365fe1844be16c8c2bb2c4ad0832d2175eac46591283af567f8efd491/diff",
"MergedDir": "/var/lib/docker/overlay2/99549b82dea04814af5b2a2c0cfa91b6a1e078f1a86335383fc0e650f43c8ae4/merged",
"UpperDir": "/var/lib/docker/overlay2/99549b82dea04814af5b2a2c0cfa91b6a1e078f1a86335383fc0e650f43c8ae4/diff",
"WorkDir": "/var/lib/docker/overlay2/99549b82dea04814af5b2a2c0cfa91b6a1e078f1a86335383fc0e650f43c8ae4/work"
},
"Name": "overlay2"
},
"Mounts": [
{
"Type": "bind",
"Source": "/tmp/host_data",
"Destination": "/tmp/docker_data",
"Mode": "",
"RW": true,
"Propagation": "rprivate"
}
]
}
]
另外当容器stop后，在宿主机上进行文件修改，这些修改同样会同步到容器中。
读写规则映射添加说明
- 读写（默认）命令：
docker run -it --privileged=true -v /宿主机绝对路径目录:/容器内目录:rw 镜像名
- 只读命令：
容器实例内部被限制，只能读不能写，此时如果宿主机写入内容可以同步到容器中，容器内可以读，但是没有写的功能。
docker run -it --privileged=true -v /宿主机绝对路径目录:/容器内目录:ro 镜像名
容器数据卷的继承和共享
容器1完成和宿主机的映射
[root@192 ~]# docker run -it --privileged=true -v /tmp/host_data:/tmp/docker_data --name=u1 ubuntu
root@6f9775c9af9a:/# pwd
/
root@6f9775c9af9a:/# cd /tmp
root@6f9775c9af9a:/tmp# ll
total 0
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ./
drwxr-xr-x. 1 root root 17 Apr 8 14:33 ../
drwxr-xr-x. 2 root root 6 Apr 8 14:33 docker_data/
[root@192 host_data]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6f9775c9af9a ubuntu "bash" 19 minutes ago Up 19 minutes u1
实现了容器和宿主机的映射。
容器2继承容器1的卷规则
docker run -it --privileged=true --volumes-from 父类 镜像名
[root@192 host_data]# docker run -it --privileged=true --volumes-from u1 --name u2 ubuntu /bin/bash
root@d25e7bd306ac:/# cd /tmp/docker_data/
root@d25e7bd306ac:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 40 Apr 8 14:54 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:56 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 14:54 kd.txt
[root@192 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d25e7bd306ac ubuntu "/bin/bash" 47 seconds ago Up 45 seconds u2
6f9775c9af9a ubuntu "bash" 24 minutes ago Up 24 minutes u1
#这里可以看到生成了u2
#在u2容器中，创建文件
root@d25e7bd306ac:/tmp/docker_data# touch kd_u2.txt
root@d25e7bd306ac:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 57 Apr 8 14:58 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:56 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 14:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 14:58 kd_u2.txt
#查看u1中是否存在
root@6f9775c9af9a:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 57 Apr 8 14:58 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 14:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 14:58 kd_u2.txt
#查看宿主机中是否存在
[root@192 host_data]# ll
total 0
-rw-r--r--. 1 root root 0 Apr 8 07:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 07:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 07:58 kd_u2.txt
#同理，在宿主机、u1上创建，在其他的上也可以看到
退出u1容器，u2和宿主机之前的映射是否还有？
[root@192 host_data]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d25e7bd306ac ubuntu "/bin/bash" 4 minutes ago Up 4 minutes u2
#退出u1
#在u2中创建文件
root@d25e7bd306ac:/tmp/docker_data# touch kd_test.txt
root@d25e7bd306ac:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 76 Apr 8 15:01 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:56 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 14:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 15:01 kd_test.txt
-rw-r--r--. 1 root root 0 Apr 8 14:58 kd_u2.txt
#宿主机
[root@192 host_data]# ll
total 0
-rw-r--r--. 1 root root 0 Apr 8 07:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 08:01 kd_test.txt
-rw-r--r--. 1 root root 0 Apr 8 07:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 07:58 kd_u2.txt
#同样生成了kd_test.txt文件
#重新启动u1容器，查看文件
[root@192 host_data]# docker ps -n 2
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
d25e7bd306ac ubuntu "/bin/bash" 6 minutes ago Up 6 minutes u2
6f9775c9af9a ubuntu "bash" 30 minutes ago Exited (0) 3 minutes ago u1
[root@192 host_data]# docker start 6f9775c9af9a
6f9775c9af9a
[root@192 host_data]# docker exec -it 6f9775c9af9a /bin/bash
root@6f9775c9af9a:/# cd /tmp/docker_data/
root@6f9775c9af9a:/tmp/docker_data# ll
total 0
drwxr-xr-x. 2 root root 76 Apr 8 15:01 ./
drwxrwxrwt. 1 root root 25 Apr 8 14:33 ../
-rw-r--r--. 1 root root 0 Apr 8 14:36 dockerin.txt
-rw-r--r--. 1 root root 0 Apr 8 14:54 kd.txt
-rw-r--r--. 1 root root 0 Apr 8 15:01 kd_test.txt
-rw-r--r--. 1 root root 0 Apr 8 14:58 kd_u2.txt
#可以看到同样生成了。