dockerd -D --storage-driver zfs
...
zfs command is not available: exec: "zfs": executable file not found in $PATH  storage-driver=zfs
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apt-get install zfsutils-linux --no-install-recommends

dockerd -D --storage-driver zfs
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DEBU[2020-05-06T16:37:51.502473451Z] cannot open /dev/zfs: open /dev/zfs: no such file or directory  storage-driver=zfs
...