docker的默认存储目录是/var/lib/docker,目录结构如下：

    [root@ztscshop docker]# cd /var/lib/docker
    [root@ztscshop docker]# ll
    total 64
    drwx------  2 root root  4096 Jan 24  2019 builder
    drwx------  4 root root  4096 Jan 24  2019 buildkit
    drwx--x--x  3 root root  4096 Jan 24  2019 containerd
    drwx------  4 root root  4096 Oct 24 15:05 containers
    drwx------  3 root root  4096 Jan 24  2019 image
    drwxr-x---  3 root root  4096 Jan 24  2019 network
    drwx------ 80 root root 16384 Oct 24 15:25 overlay2
    drwx------  4 root root  4096 Jan 24  2019 plugins
    drwx------  2 root root  4096 Oct 22 11:57 runtimes
    drwx------  2 root root  4096 Jan 24  2019 swarm
    drwx------  2 root root  4096 Oct 24 15:13 tmp
    drwx------  2 root root  4096 Jan 24  2019 trust
    drwx------ 15 root root  4096 Feb  7  2019 volumes
    [root@ztscshop docker]# 

docker所有自身的东西都会存在这些文件夹下面包括镜像文件和容器，所以会占用越来越多的磁盘空间。

如果docker所在的磁盘空间比较小，磁盘空间被占满没有空间的时候，显然会导致docker容器运行失败，此时必然要迁移docker的存储目录到一个更大的磁盘下面。

1.查看磁盘占用情况：df -h

    [root@ecs-8f49 ~]# df -h
    Filesystem      Size  Used Avail Use% Mounted on
    devtmpfs        7.8G     0  7.8G   0% /dev
    tmpfs           7.8G     0  7.8G   0% /dev/shm
    tmpfs           7.8G   73M  7.7G   1% /run
    tmpfs           7.8G     0  7.8G   0% /sys/fs/cgroup
    /dev/vda1        40G   13G   25G  33% /
    tmpfs           1.6G     0  1.6G   0% /run/user/0
    overlay          40G   13G   25G  33% /var/lib/docker/overlay2/53eb033fae8fadc98df74b118e743092fcd0ee68b579c2b771288c3c023b0b8b/merged
    shm              64M     0   64M   0% /var/lib/docker/containers/8ecb90f024c08468c5f32e7c8b8b0d1ff87616536e6c2155cfb58447bded3071/shm

2.查看docker自身的内存占用：docker system df

    [root@ecs-8f49 ~]# docker system df
    TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
    Images              16                  12                  2.893 GB            1.535 GB (53%)
    Containers          12                  1                   155.6 MB            155.6 MB (100%)
    Local Volumes       1                   1                   4.212 GB            0 B (0%)

3.docker system prune命令可以用于清理磁盘，删除关闭的容器、无用的数据卷和网络，以及dangling镜像(即无tag的镜像)。

    [root@ecs-8f49 ~]# docker system prune
    WARNING! This will remove:
        - all stopped containers
        - all volumes not used by at least one container
        - all networks not used by at least one container
        - all dangling images
    Are you sure you want to continue? [y/N] y
    Deleted Containers:
    9bd48276fcd28b3882605fd67a156a7ea848f8fbfe16c3588b630955dfda253d
    74af4504bdefbc58b83a476c12d6ce10260f91349eed0e5bfca5e51b86fb8474
    d405d43eeb7908472b4b8712f668ca3b97f3796f6afc1c1d19a15879140ddf64
    9f645670de22840d04249351d07b2f68f77754e4dfebdb4b39c56d827d6b6805
    79d32c6b3c34bb359cbbf8309d7be34074da391d3b48083f456a5911259a5213
    ad7137d7e018144e17790a3c86a8217a95faecd07a39003bc4df275c8c8d351d
    b02eb42677a52663e50fc4a2b1344d37a8d2a2cca445fe5eae49648a0ca54b13
    0813454a5421cf380b72265c2e6832411a590479424dbc3470e47e1cc9cdd740
    a58b5f545ce1cd03a2899ba277641b5f52203802d9672c72f281f2d5a31fc219
    936e65f72c60d754cb2a1441d0cdeb18f9a7ebde353f091fc44a034733fed52c
    ad86565bd85af04f5847703ba213d226c7d7b69e5210211e4170671d3ea4051c

    Deleted Volumes:
    37620879ca58c052c47e7677a1851f45c25cbc0437c8883cc2fe8e70e1cb921a

    Total reclaimed space: 4.368 GB

4.docker system prune -a命令清理得更加彻底，可以将没有容器使用Docker镜像都删掉。注意，这两个命令会把你暂时关闭的容器，以及暂时没有用到的Docker镜像都删掉了…所以使用之前一定要想清楚.。我没用过，因为会清理 没有开启的 Docker 镜像。

5.迁移/var/lib/docker目录。

5.1 停止docker服务

    systemctl stop docker

5.2 创建新的docker目录，执行命令df -h,找一个大的磁盘。 我在 /home目录下面建了 /home/docker/lib目录，执行的命令是：

    mkdir -p /home/docker/lib

5.3 迁移/var/lib/docker目录下面的文件到 /home/docker/lib：

(rsync是linux文件夹同步的命令，参数要加一个-r,因为文件夹要递归copy，如果在同一台服务器上面，直接cp也是可以的)

 

    rsync -r -avz /var/lib/docker /home/docker/lib/

5.4 配置 /etc/systemd/system/docker.service.d/devicemapper.conf。查看 devicemapper.conf 是否存在。如果不存在，就新建。

    mkdir -p /etc/systemd/system/docker.service.d/
    vi /etc/systemd/system/docker.service.d/devicemapper.conf

5.5 然后在 devicemapper.conf 写入：（同步的时候把父文件夹一并同步过来，实际上的目录应在 /home/docker/lib/docker ）

    [Service]
    ExecStart=
    ExecStart=/usr/bin/dockerd --graph=/home/docker/lib/docker

5.6 重新加载 docker

    systemctl daemon-reload

    systemctl restart docker

    systemctl enable docker

5.7 为了确认一切顺利，运行

    docker info

命令检查Docker 的根目录.它将被更改为 /home/docker/lib/docker

    ...
    Docker Root Dir: /home/docker/lib/docker
    Debug Mode (client): false
    Debug Mode (server): false
    Registry: https://index.docker.io/v1/
    ...

5.8 启动成功后，再确认之前的镜像还在：

    root@nn0:~$ docker images
    REPOSITORY TAG IMAGE ID CREATED SIZE
    AAA/AAA v2 7331b8651bcc 27 hours ago 3.85GB
    BBB/BBB v1 da4a80dd8424 28 hours ago 3.47GB

5.9 确定容器没问题后删除/var/lib/docker/目录中的文件。

6.迁移/var/lib/docker目录后，Docker无法启动 (error initializing graphdriver: driver not supported)

启动信息

    [root@nn0 ~]# systemctl start docker
    Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.

启动详情

    8月 31 01:47:25 localhost.localdomain systemd[1]: Starting Docker Application Container Engine...
    -- Subject: Unit docker.service has begun start-up
    -- Defined-By: systemd
    -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
    -- 
    -- Unit docker.service has begun starting up.
    8月 31 01:47:25 localhost.localdomain dockerd[2390]: time="2018-08-31T01:47:25.197015872+08:00" level=info msg="libcontainerd: new containerd process, pid: 2393"
    8月 31 01:47:26 localhost.localdomain dockerd[2390]: time="2018-08-31T01:47:26.204103195+08:00" level=error msg="[graphdriver] prior storage driver overlay2 failed: driver not supported"
    8月 31 01:47:26 localhost.localdomain dockerd[2390]: Error starting daemon: error initializing graphdriver: driver not supported
    8月 31 01:47:26 localhost.localdomain systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
    8月 31 01:47:26 localhost.localdomain systemd[1]: Failed to start Docker Application Container Engine.

错误原因：error initializing graphdriver: driver not supported

解决办法：在 /etc/docker 目录下创建daemon.json文件，并且加入以下配置

    touch daemon.json
    vi daemon.json
    {
      "storage-driver": "overlay2",
      "storage-opts": [
        "overlay2.override_kernel_check=true"
      ]
    }

再次启动：systemctl start docker

7. docker-runc not installed on system 问题

问题描述

docker运行镜像的时候，报错如下：
(如果报错端口映射的错误，那就先不映射端口直接启动镜像，试一下是不是这个错误，因为如果直接映射端口启动镜像的话，这个错误导致容器启动失败，但是报错是端口映射失败)

    [root@nn0 k8s]# docker run -it registry.helloworld.com/test/atsd:latest bash
    WARNING: IPv4 forwarding is disabled. Networking will not work.
    /usr/bin/docker-current: Error response from daemon: shim error: docker-runc not installed on system.

问题解决：

    [root@nn0 k8s]# cd /usr/libexec/docker/
    [root@nn0 docker]# ln -s docker-runc-current docker-runc