Docker start failed in centos 7 - linux

Question

Docker service running on Centos 7 failed to start, I have some docker images which I want to save at any cost. I have searched a couple of online docs and they all say to delete /var/lib/docker/ dir which I don't want to because all the images and containers stuff is there. Can someone please save me how to get docker back up and running with losing any data.
Log:
[root#BuyPandGDev01 /]# systemctl status docker.service -l
● docker.service - Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Sun 2018-04-22 00:05:23 UTC; 19min ago
Docs: http://docs.docker.com
Process: 1539 ExecStart=/usr/bin/dockerd-current --add-runtime docker-runc=/usr/libexec/docker/docker-runc-current --default-runtime=docker-runc --exec-opt native.cgroupdriver=systemd --userland-proxy-path=/usr/libexec/docker/docker-proxy-current $OPTIONS $DOCKER_STORAGE_OPTIONS $DOCKER_NETWORK_OPTIONS $ADD_REGISTRY $BLOCK_REGISTRY $INSECURE_REGISTRY $REGISTRIES (code=exited, status=1/FAILURE)
Main PID: 1539 (code=exited, status=1/FAILURE)
Apr 22 00:05:22 BuyPandGDev01 systemd[1]: Starting Docker Application Container Engine...
Apr 22 00:05:22 BuyPandGDev01 dockerd-current[1539]: time="2018-04-22T00:05:22.068920976Z" level=info msg="libcontainerd: new containerd process, pid: 1550"
Apr 22 00:05:23 BuyPandGDev01 dockerd-current[1539]: time="2018-04-22T00:05:23.101036303Z" level=warning msg="devmapper: Usage of loopback devices is strongly discouraged for production use. Please use `--storage-opt dm.thinpooldev` or use `man docker` to refer to dm.thinpooldev section."
Apr 22 00:05:23 BuyPandGDev01 dockerd-current[1539]: time="2018-04-22T00:05:23.155223108Z" level=error msg="[graphdriver] prior storage driver \"devicemapper\" failed: devmapper: Base Device UUID and Filesystem verification failed: devicemapper: Error running deviceCreate (ActivateDevice) dm_task_run failed"
Apr 22 00:05:23 BuyPandGDev01 dockerd-current[1539]: time="2018-04-22T00:05:23.155708413Z" level=fatal msg="Error starting daemon: error initializing graphdriver: devmapper: Base Device UUID and Filesystem verification failed: devicemapper: Error running deviceCreate (ActivateDevice) dm_task_run failed"
Apr 22 00:05:23 BuyPandGDev01 systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Apr 22 00:05:23 BuyPandGDev01 systemd[1]: Failed to start Docker Application Container Engine.
Apr 22 00:05:23 BuyPandGDev01 systemd[1]: Unit docker.service entered failed state.
Apr 22 00:05:23 BuyPandGDev01 systemd[1]: docker.service failed.
journalctl -xe:
[root#BuyPandGDev01 /]# journalctl -xe
-- Unit docker-storage-setup.service has begun starting up.
Apr 22 00:25:58 BuyPandGDev01 container-storage-setup[2111]: INFO: Volume group backing root filesystem could not be determined
Apr 22 00:25:58 BuyPandGDev01 container-storage-setup[2111]: ERROR: No valid volume group found. Exiting.
Apr 22 00:25:58 BuyPandGDev01 systemd[1]: docker-storage-setup.service: main process exited, code=exited, status=1/FAILURE
Apr 22 00:25:58 BuyPandGDev01 systemd[1]: Failed to start Docker Storage Setup.
-- Subject: Unit docker-storage-setup.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker-storage-setup.service has failed.
--
-- The result is failed.
Apr 22 00:25:58 BuyPandGDev01 systemd[1]: Unit docker-storage-setup.service entered failed state.
Apr 22 00:25:58 BuyPandGDev01 systemd[1]: docker-storage-setup.service failed.
Apr 22 00:25:58 BuyPandGDev01 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.
Apr 22 00:25:58 BuyPandGDev01 dockerd-current[2140]: time="2018-04-22T00:25:58.731142431Z" level=info msg="libcontainerd: new containe
Apr 22 00:25:59 BuyPandGDev01 dockerd-current[2140]: time="2018-04-22T00:25:59.767061431Z" level=warning msg="devmapper: Usage of loop
Apr 22 00:25:59 BuyPandGDev01 kernel: device-mapper: table: 253:1: thin: Couldn't open thin internal device
Apr 22 00:25:59 BuyPandGDev01 kernel: device-mapper: ioctl: error adding target to table
Apr 22 00:25:59 BuyPandGDev01 dockerd-current[2140]: time="2018-04-22T00:25:59.835261589Z" level=error msg="[graphdriver] prior storag
Apr 22 00:25:59 BuyPandGDev01 dockerd-current[2140]: time="2018-04-22T00:25:59.835697590Z" level=fatal msg="Error starting daemon: err
Apr 22 00:25:59 BuyPandGDev01 systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Apr 22 00:25:59 BuyPandGDev01 systemd[1]: Failed to start Docker Application Container Engine.
-- Subject: Unit docker.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit docker.service has failed.
--
-- The result is failed.
Apr 22 00:25:59 BuyPandGDev01 systemd[1]: Unit docker.service entered failed state.
Apr 22 00:25:59 BuyPandGDev01 systemd[1]: docker.service failed.
Apr 22 00:25:59 BuyPandGDev01 polkitd[703]: Unregistered Authentication Agent for unix-process:2105:147803 (system bus name :1.43, obj
lines 2751-2788/2788 (END)
Any response would be helpful and appreciated.
Thx,
kumar

Answer 1

This error occurred for me when I was upgrading docker. Solution that worked for me was to remove legacy docker files /var/lib/docker/ and restart the docker service. Here is the solution.
# Remove docker files
$ rm -rf /var/lib/docker/
# Restart docker via service or via systemctl
$ service docker restart
$ service docker status
$ systemctl start docker.service
$ systemctl status docker.service

Answer 2

I had this error also starting the docker service:
kernel: device-mapper: table: 253:1: thin: Couldn't open thin internal device
I fixed it by creating a soft link from /var/lib/docker to another location on the machine which had more disk space.
cd /var/lib/
mv docker docker.old
ln -s /path/to/big/disk/docker/ docker
Restart the service:
systemctl restart docker