Why is docker image eating up my disk space that is not used by docker

Question

I have setup docker and I have used completely different block device to store docker's system data:

[root@blink1 /]# cat /etc/sysconfig/docker
# /etc/sysconfig/docker
other_args="-H tcp://0.0.0.0:9367 -H unix:///var/run/docker.sock -g /disk1/docker"
Note that /disk/1 is using a completely different hard drive /dev/xvdi
Filesystem      Size  Used Avail Use% Mounted on
/dev/xvda1      7.8G  5.1G  2.6G  67% /
devtmpfs        1.9G  108K  1.9G   1% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
/dev/xvdi        20G  5.3G   15G  27% /disk1
/dev/dm-1       9.8G  1.7G  7.6G  18% /disk1/docker/devicemapper/mnt/bb6c540bae25aaf01aedf56ff61ffed8c6ae41aa9bd06122d440c6053e3486bf
/dev/dm-2       9.8G  1.7G  7.7G  18% /disk1/docker/devicemapper/mnt/c85f756c59a5e1d260c3cdb473f3f4d9e55ac568967abe190eeaf9c4087afeac

The problem is that when I continue download docker images and run docker containers, it seems that the other hard drive /dev/xvda1 is also used up.

Answer 1

It's a kernel problem with devicemapper, which affects the RedHat family of OS (RedHat, Fedora, CentOS, and Amazon Linux). Deleted containers don't free up mapped disk space. This means that on the affected OSs you'll slowly run out of space as you start and restart containers.

uninstall docker, then delete all its files, then reinstall:

sudo yum remove docker
sudo rm -rf /var/lib/docker
sudo yum install docker

Answer 2

Move the /var/llib/docker directory.

Assuming the /root directory has enough room, if not, substitute for one that does,

sudo systemctl stop docker
mv /usr/lib/docker /root
ln -s /root/docker /var/lib/docker
systemctl start docker