Docker数据卷

最新推荐文章于 2025-02-26 11:38:36 发布

置顶 OPS_akai

最新推荐文章于 2025-02-26 11:38:36 发布

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分类专栏： Docker linux运维文章标签： docker 容器运维

本文链接：https://blog.youkuaiyun.com/OPS_akai/article/details/121973771

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什么是数据卷

它是为一个或多个容器使用的特殊目录或文件，可以独立于联合文件系统的形式直接在宿主机中存在，访问数据提供方便。

为什么使用数据卷

***数据持久性：***当容器删除后，容器产生的数据也会丢失，使用数据卷会独立于容器存在，删除容器，volume仍然存在
***数据共享：***多容器之间数据共享，对数据卷中数据操作会立马生效.
2容器删除，数据不会删除，volume依然存在。

如何使用

1使用-v （-v /path）
docker run -it --name app_volume1 -v /docker/aaa/ nginx /bin/bash
**解释：**容器名：app_volume1
-v：使用数据卷，启动容器会使用容器下的该目录
没有该目录会自动创建。

[root@wck _data]# docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS         PORTS     NAMES
8789e03b7b2b   nginx     "/docker-entrypoint.…"   6 minutes ago   Up 6 minutes   80/tcp    nginx-volume

此时会创建一个容器，在容器下会有/docker/aaa/目录

[root@wck _data]# docker exec -it 87 /bin/bash
root@8789e03b7b2b:/#                 
root@8789e03b7b2b:/# cd /docker/volume-test/    
root@8789e03b7b2b:/docker/volume-test# ls
aaa

让后查看在容器中的数据映射到宿主机的位置：

[root@wck volume-test]# docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS         PORTS     NAMES
8789e03b7b2b   nginx     "/docker-entrypoint.…"   2 minutes ago   Up 2 minutes   80/tcp    nginx-volume
[root@wck volume-test]# docker inspect 87
[
    {
        "Id": "8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51",
        "Created": "2021-12-16T06:38:07.716117382Z",
        "Path": "/docker-entrypoint.sh",
        "Args": [
            "/bin/bash"
        ],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 7157,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2021-12-16T06:38:08.044030586Z",
            "FinishedAt": "0001-01-01T00:00:00Z"
        },
        "Image": "sha256:ea335eea17ab984571cd4a3bcf90a0413773b559c75ef4cda07d0ce952b00291",
        "ResolvConfPath": "/var/lib/docker/containers/8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51/hostname",
        "HostsPath": "/var/lib/docker/containers/8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51/hosts",
        "LogPath": "/var/lib/docker/containers/8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51/8789e03b7b2b7cf8e22ab1ed6d3393eea19b2183af7556e7307556c697186a51-json.log",
        "Name": "/nginx-volume",
        "RestartCount": 0,
        "Driver": "overlay2",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "",
        "ExecIDs": [
            "7b595495362d354e7917fca566e01cc10c2b7725e6c7d59f48c0525655943a2e"
        ],
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "default",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "CapAdd": null,
            "CapDrop": null,
            "CgroupnsMode": "host",
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "private",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "ConsoleSize": [
                0,
                0
            ],
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": null,
            "BlkioDeviceWriteBps": null,
            "BlkioDeviceReadIOps": null,
            "BlkioDeviceWriteIOps": null,
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DeviceRequests": null,
            "KernelMemory": 0,
            "KernelMemoryTCP": 0,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": false,
            "PidsLimit": null,
            "Ulimits": null,
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0,
            "MaskedPaths": [
                "/proc/asound",
                "/proc/acpi",
                "/proc/kcore",
                "/proc/keys",
                "/proc/latency_stats",
                "/proc/timer_list",
                "/proc/timer_stats",
                "/proc/sched_debug",
                "/proc/scsi",
                "/sys/firmware"
            ],
            "ReadonlyPaths": [
                "/proc/bus",
                "/proc/fs",
                "/proc/irq",
                "/proc/sys",
                "/proc/sysrq-trigger"
            ]
        },
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/19eb35424d9c6a5d904d678a51f7e045ec8b19b38eda39e8f7ea1d10b4500ff0-init/diff:/var/lib/docker/overlay2/0f4ce30266b8025ff7ec8f1994f70595d85387c1ab1389db5c33395b7534f9a5/diff:/var/lib/docker/overlay2/7705948e02485a31cb3abead19ea7014e2813e5e63e36b2f4d9bdb874d35c097/diff:/var/lib/docker/overlay2/cc6e0e98c0b954e21b18c2a50646c1635076be919bc211065166db7ca384a576/diff:/var/lib/docker/overlay2/94ccdf8150aa64f49ba7354c0a1be1dc91c6396a524b13bb5f1798880ac18d1f/diff:/var/lib/docker/overlay2/1cb64c6b87a8865b7eb1cc1870513f92fd8517793841935f9fb21c0403da773c/diff:/var/lib/docker/overlay2/9d2a9c13f0a75e59cacd04931b7c870aa96302e73bb513eee7e5dd4b62923f3f/diff",
                "MergedDir": "/var/lib/docker/overlay2/19eb35424d9c6a5d904d678a51f7e045ec8b19b38eda39e8f7ea1d10b4500ff0/merged",
                "UpperDir": "/var/lib/docker/overlay2/19eb35424d9c6a5d904d678a51f7e045ec8b19b38eda39e8f7ea1d10b4500ff0/diff",
                "WorkDir": "/var/lib/docker/overlay2/19eb35424d9c6a5d904d678a51f7e045ec8b19b38eda39e8f7ea1d10b4500ff0/work"
            },
            "Name": "overlay2"
        },
        "Mounts": [
            {
                "Type": "volume",
                "Name": "2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e",
                "Source": "/var/lib/docker/volumes/2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e/_data",
                "Destination": "/docker/volume-test",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
        "Config": {
            "Hostname": "8789e03b7b2b",
            "Domainname": "",
            "User": "",
            "AttachStdin": true,
            "AttachStdout": true,
            "AttachStderr": true,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": true,
            "OpenStdin": true,
            "StdinOnce": true,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.21.4",
                "NJS_VERSION=0.7.0",
                "PKG_RELEASE=1~bullseye"
            ],
            "Cmd": [
                "/bin/bash"
            ],
            "Image": "nginx",
            "Volumes": {
                "/docker/volume-test/": {}
            },
            "WorkingDir": "",
            "Entrypoint": [
                "/docker-entrypoint.sh"
            ],
            "OnBuild": null,
            "Labels": {
                "maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
            },
            "StopSignal": "SIGQUIT"
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "7bba9839558d8e58e95fa9327b921039c88d304abb67a6a1f3901fbc8c641313",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "Ports": {
                "80/tcp": null
            },
            "SandboxKey": "/var/run/docker/netns/7bba9839558d",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "51c1c77d76d975bbef0aabf0de6e86a771b618fd8da9690700f4fff24b7307f5",
            "Gateway": "172.17.0.1",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "172.17.0.2",
            "IPPrefixLen": 16,
            "IPv6Gateway": "",
            "MacAddress": "02:42:ac:11:00:02",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "62bd543861f2e76f7e15e116557b40c327f17fcf633c347683d9761ab79432b1",
                    "EndpointID": "51c1c77d76d975bbef0aabf0de6e86a771b618fd8da9690700f4fff24b7307f5",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:11:00:02",
                    "DriverOpts": null
                }
            }
        }
    }
]
[root@wck volume-test]#

 "Mounts": [
            {
                "Type": "volume",
                "Name": "2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e",
                "Source": "/var/lib/docker/volumes/2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e/_data",
                "Destination": "/docker/volume-test",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],

此时在文件Mounts位置就是宿主机数据卷的位置,会发现也有在容器创建的文件aaa。而且是同步存在的

[root@wck volume-test]# cd /var/lib/docker/volumes/2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e/
[root@wck 2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e]# ls
_data
[root@wck 2e905a3a4762191a18ac74df5af24276bf245c0baabe9c31fbbef4a5d4bc9e9e]# cd _data/
[root@wck _data]# ls
aaa
[root@wck _data]#

注意：
利用docker commit生成新镜像，然后docker run -it 运行新镜像，发现容器挂载目录下没有任何文件了。说明生成新镜像时，是不保存挂载文件的。

2使用-v (-v /宿主path:/容器path)
将主机的文件或文件夹作为volume挂载时，可以用多个 -v标签为容器添加多个volume，还可以使用:ro指定该volume为只读。
注意：
如果容器中指定的挂载目录存在相同的文件时，会被宿主机覆盖掉。

创建挂载两个数据卷，一个rw一个ro的容器-使用inspect查看详细信息

[root@wck _data]# docker run -it --name nginx1-volume -v /docker/aaa1/:/docker/volume-test1 -v /docker/aaa2/:/docker/volume-test2:ro  nginx /bin/bash
root@b99cdcd68017:/#

3 使用dockerfile

使用VOLUME指令添加：
单个：
VOLUME /docker/aaa
多个VOLUME：
VOLUME ["/docker/aaa,/docker/bbb"]
以上和docker run -v /docker/aaa是一样效果
注意
1dockerfile中使用volume是不能和第二种方法那样挂载宿主机中指定的文件夹。这时为了保证Dockerfile的可移植性，因为不能保证所有的宿主机都有对应的文件夹。
2需要注意的是，在Dockerfile中使用VOLUME指令后，如果尝试对这个volume进行修改，这些修改指令都不会生效，比如下面例子，尝试添加一个文件，并修改文件并改变文件所有权限

FROM test/mycent:v1.0
RUN useradd foo 
VOLUME /data 
RUN touch /data/x 
RUN chown -R foo:foo /data

共享volume/数据卷容器(–volumes-from)

如果你有一些持续更新的数据需要在容器之间共享，最好创建数据卷容器。数据卷容器，其实就是一个正常的容器，专门用来提供数据卷供其它容器挂载的。
先创建一个名为dbdata的数据卷容器，专门共其他容器挂载。并创建共享文件。

[root@wck ~]# docker run -it --name DB -v /opt/docker nginx /bin/bash
root@7008f662852b:/# 
root@7008f662852b:/opt# cd docker/

root@7008f662852b:/opt/docker# echo 33434343434 > aa
root@7008f662852b:/opt/docker# ls
aa

再启动其他两个容器并把DB挂载：
容器aaa1和容器aaa2

[root@wck ~]# docker run -itd --name aaa1 --volumes-from DB nginx /bin/bash
[root@wck ~]# docker run -itd --name aaa2 --volumes-from DB nginx /bin/bash

在这两个容器下面就都能看到DB容器的/opt/docker/下的共享文件，而且实现同步。
查看inspect
aaa1的

"Mounts": [
            {
                "Type": "volume",
                "Name": "97344c638fe5a777ba123b188018d10c508cd2e900740a2e1373970a5ba5e568",
                "Source": "/var/lib/docker/volumes/97344c638fe5a777ba123b188018d10c508cd2e900740a2e1373970a5ba5e568/_data",
                "Destination": "/opt/docker",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }

aaa2的

"Mounts": [
            {
                "Type": "volume",
                "Name": "97344c638fe5a777ba123b188018d10c508cd2e900740a2e1373970a5ba5e568",
                "Source": "/var/lib/docker/volumes/97344c638fe5a777ba123b188018d10c508cd2e900740a2e1373970a5ba5e568/_data",
                "Destination": "/opt/docker",
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }