[轉]關於docker包存儲結構說明

原文：http://blog.csdn.net/w412692660/article/details/49005631

 

 

前段時間與同事交流docker的安裝包層次結構,並溝通相關每一個文件的做用,可是一直沒有進行文字備份,過去已經一月有餘,仍是將其記錄下來,供後續工做參考

 

默認docker啓動會將目錄安裝在/var/lib/docker中,不過建議能夠修改 --graph="/path/docker"安裝目錄.

防止系統盤空間佔用過大,最好選擇存儲空間較大的分區.

 

docker目錄:

containers  當前容器的集合(至關於docker ps -a)

目錄是容器的配置信息及當前狀態.

經常使用的包括容器配置信息, 網絡信息,日誌,都是來源於此,默認存儲方式json

咱們平時使用的docker inspect , docker logs, docker ps 都是來自於文件夾

 通常用於docker容器重啓時,恢復配置使用的依據,因爲掛起方式是基礎環境,沒有辦法像VM軟件的掛起能夠凍結進程,也是docker相似半虛擬容器很難實現真正的將運行容器進行分發,故此若是想實現有狀態的運行容器漂移是還是十分困難.

 

 

 

hostname 主機名稱

hosts 容器重啓

resolv.conf是DNS服務,默認是拷貝/etc/resolv.conf的配置

hostconfig.json是核心配置之一, 包括網絡, CPU, MEM等,dockerrun選項配置造成的容器設置均可以在此處查詢到.

config.json是核心docker狀態管理文件, 由她加載上述全部文件

config.json 是核心docker狀態管理文件, 由她加載上述全部文件

 

 

{
    "State": {
        "Running": false,
        "Paused": false,
        "Restarting": false,
        "OOMKilled": false,
        "Dead": false,
        "Pid": 0,
        "ExitCode": 0,
        "Error": "",
        "StartedAt": "2015-10-10T07:36:31.250795069Z",
        "FinishedAt": "2015-10-10T07:37:09.587772608Z"
    },
    "ID": "02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def",
    "Created": "2015-10-10T07:36:30.400677786Z",
    "Path": "/bin/bash",
    "Args": [],
    "Config": {
        "Hostname": "02bbc65a5c2a",
        "Domainname": "",
        "User": "",
        "AttachStdin": true,
        "AttachStdout": true,
        "AttachStderr": true,
        "PortSpecs": null,
        "ExposedPorts": null,
        "Tty": true,
        "OpenStdin": true,
        "StdinOnce": true,
        "Env": null,
        "Cmd": [
            "/bin/bash"
        ],
        "Image": "docker.io/coreos/apache",
        "Volumes": {
            "/data0": {}
        },
        "VolumeDriver": "",
        "WorkingDir": "",
        "Entrypoint": null,
        "NetworkDisabled": false,
        "MacAddress": "",
        "OnBuild": null,
        "Labels": {}
    },
    "Image": "87026dcb00443eb7f1725b1c9f4fb8210027a19364103854a1e5f606b95019ff",
    "NetworkSettings": {
        "Bridge": "",
        "EndpointID": "",
        "Gateway": "",
        "GlobalIPv6Address": "",
        "GlobalIPv6PrefixLen": 0,
        "HairpinMode": false,
        "IPAddress": "",
        "IPPrefixLen": 0,
        "IPv6Gateway": "",
        "LinkLocalIPv6Address": "",
        "LinkLocalIPv6PrefixLen": 0,
        "MacAddress": "",
        "NetworkID": "",
        "PortMapping": null,
        "Ports": null,
        "SandboxKey": "",
        "SecondaryIPAddresses": null,
        "SecondaryIPv6Addresses": null
    },
    "ResolvConfPath": "/var/lib/docker/containers/02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def/resolv.conf",
    "HostnamePath": "/var/lib/docker/containers/02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def/hostname",
    "HostsPath": "/var/lib/docker/containers/02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def/hosts",
    "LogPath": "/var/lib/docker/containers/02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def/02bbc65a5c2a285c34565fd9b0b3b485772faaf968a2f2eb3df1fff649119def-json.log",
    "Name": "/determined_poincare",
    "Driver": "devicemapper",
    "ExecDriver": "native-0.2",
    "MountLabel": "",
    "ProcessLabel": "",
    "RestartCount": 0,
    "UpdateDns": false,
    "MountPoints": {
        "/data0": {
            "Name": "53938b2752dc6f84475657a57ce87d45a329d3815426c1f0988c18b6bbf2df86",
            "Destination": "/data0",
            "Driver": "local",
            "RW": true,
            "Source": "",
            "Relabel": ""
        }
    },
    "Volumes": {},
    "VolumesRW": {},
    "AppArmorProfile": ""
}

XXX.log  是容器log日誌,也僅有啓動容器時,運行命令的日誌,其餘如後臺程序的日誌並不在此日誌中.

 

devicemapper 是以ID爲標識存儲鏡像和容器,能夠說devicemapper是最核心的部分,同時也是最容易存儲超標的部分,其是lvm的軟件之docker主要用了他的快照功能,完成image的思想基石,containers和image的json文件都是描述,真正存儲數據的則是devicemapper/data.

 

其中包括臨時容器和鏡像文件, 儘管咱們是容器內部的文件拷貝,也會促使data文件的增大,後續打算找個專題來解釋他吧,docker的封裝devicemapper的API是很不錯,有興趣能夠參考/github.com/docker/docker/daemon/graphdriver/devmapper/driver.go , 僅僅對外暴漏數個接口,具體實現deviceset.go中.

 

graph 存儲鏡像信息,使用json方式存儲描述,真正數據也是存儲在devicemapper中,鏡像ID則是devicemapper存儲的ID.

 

devicemapper , 具體可參考:graph.go的Register(img*image.Image,layerDataio.Reader)函數

鏡像內容包括:鏡像ID,父鏡像ID,父鏡像的容器,另每一個鏡像都有一個初始鏡像,能夠追溯

 

// Create creates a new image and registers it in the graph.
// 建立一個新的鏡像
func (graph *Graph) Create(layerData io.Reader, containerID, containerImage, comment, author string, containerConfig, config *runconfig.Config) (*image.Image, error) {
    // 初始化鏡像實例
    img := &image.Image{
        ID:            stringid.GenerateRandomID(), // 生成鏡像ID
        Comment:       comment,  // 命令
        Created:       time.Now().UTC(), // 時間
        DockerVersion: dockerversion.VERSION, // docker版本
        Author:        author, // 做者
        Config:        config, // 相關container配置, 請查看graph/**/json
        Architecture:  runtime.GOARCH,
        OS:            runtime.GOOS,
    }


    // 非初始鏡像,則設置鏡像父子關係
    if containerID != "" {
        img.Parent = containerImage
        img.Container = containerID
        img.ContainerConfig = *containerConfig
    }


    // 註冊鏡像
    if err := graph.Register(img, layerData); err != nil {
        return nil, err
    }
    return img, nil
}

 

 

vfs 是咱們使用不定向掛載時引用,好比說咱們-v /data0 ,則默認使用vfs作爲掛載路徑,使用dockerfile時較爲經常使用

 

volumes 是掛載使用的映射關係,對應掛載源與掛載路徑的關係,同時擁有ID,用於能夠多個容器使用一個掛在源

 

linkgraph.db  是graph存儲鏡像之間的關聯關係,是初始化graph對象的依據.同時,graph文件夾的信息與linkgraph.db是數據重合的.