read-only file system 해결

[원본 참조]  https://stackoverflow.com/questions/37810293/coreos-read-only-file-system

The default path on CoreOS is /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/opt/bin. By default /opt/ and /opt/bin don't exist. Do mkdir -p /opt/bin; mv ./kubectl /opt/bin/kubectl – spuder May 23 '17 at 19:10 

신규 설치 부분은 /opt/bin 활용하여 설치해야 할 듯.