 cat /etc/certs/cert-chain.pem | openssl x509 -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            7e:b4:44:fe:d0:46:ba:27:47:5a:50:c8:f0:8e:8b:da
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: O = k8s.cluster.local
        Validity
            Not Before: Jul 13 01:23:13 2018 GMT
            Not After : Oct 11 01:23:13 2018 GMT
        Subject: O =
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Pu