docker 默认的数据存储目录为：/var/lib/docker，主要的文件是/var/lib/docker/devicemapper/devicemapper/data,该文件存储docker的镜像文件，如果镜像过多经常会导致/var使用率100%，当然如果是生产环境你可能不会使用文件系统而是使用thinpool来存储镜像文件，而且一般生产上一台机器上的docker镜像和容器一般也会不过多。

下面我们分别介绍下修改thinpool和移动/var/lib/docker的基本操作：

Docker config thin pool

about: device-mapper-driver

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systemctl stop docker
rm -rf /var/lib/docker

pvcreate /dev/vdb
vgcreate docker /dev/vdb

cat << EOF > /etc/sysconfig/docker-storage-setup
STORAGE_DRIVER=devicemapper
VG=docker
EXTRA_DOCKER_STORAGE_OPTIONS=" --storage-opt dm.use_deferred_removal=true"
EOF

docker-storage-setup

systemctl daemon-reload
systemctl start docker

Move /var/lib/docker ( centos 7 )

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systemctl stop docker

set in the /etc/sysconfig/docker file, add -g

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OPTIONS='--selinux-enabled --log-driver=journald'

to

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OPTIONS='--selinux-enabled --log-driver=journald -g /data/docker/'

the /data/docker/ is new docker directory

if /var/lib/docker have your images and want to save it. Move the data to /data/docker

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mv /var/lib/docker /data/
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systemctl start docker

link: #3127 How do I change the Docker image installation directory