CoreOSでdockerのbasesizeをかえる。

devicemapperのみ利用可能、overlay2 では使えないと思う。

##下準備
/var/lib/docker
を消す（データが消える)

##cloud init

cloud-config.ymlを作る

core20190325 core # vi cloud-config.yml

#cloud-config
coreos:
  units:
    - name: docker.service
      drop-ins:
        - name: 10-storage-opt.conf
          content: |
            [Service]
            Environment="DOCKER_OPTS=--storage-opt dm.basesize=1G"
      command: start

##読み込む

core20190325 core # coreos-cloudinit -from-file=./cloud-config.yml

あるいは

ls /etc/systemd/system/docker.service.d/
vi その中にあるファイル(e.g.10-devicemapper-storage-driver.conf)
[Service]
Environment="DOCKER_OPTS=  --storage-opt=dm.basesize=1G"

##リロード

core20190325 core # systemctl daemon-reload
core20190325 core #  systemctl stop docker

#たまに消さなくても動作しそうです。

core20190325 core # rm -rf /var/lib/docker

core20190325 core #  systemctl start docker
core20190325 core # docker info
Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
Server Version: 18.06.1-ce
Storage Driver: devicemapper
 Pool Name: docker-8:9-1042461-pool
 Pool Blocksize: 65.54kB
 Base Device Size: 1.074GB
 Backing Filesystem: xfs

#Ref
https://qiita.com/python_spameggs/items/66f6bbe4b97be55f8b65
https://coreos.com/os/docs/latest/customizing-docker.html
#See Also
https://qiita.com/haniokasai/items/2b7a1889e4930b7682c9