X1よりX2の方が新しくてかっこいいらしい

$ openssl x509 -in /etc/ssl/certs/ISRG_Root_X1.pem -noout -text | head
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            82:10:cf:b0:d2:40:e3:59:44:63:e0:bb:63:82:8b:00
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C = US, O = Internet Security Research Group, CN = ISRG Root X1
        Validity
            Not Before: Jun  4 11:04:38 2015 GMT
            Not After : Jun  4 11:04:38 2035 GMT
$ openssl x509 -in /etc/ssl/certs/ISRG_Root_X2.pem -noout -text | head
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            41:d2:9d:d1:72:ea:ee:a7:80:c1:2c:6c:e9:2f:87:52
        Signature Algorithm: ecdsa-with-SHA384
        Issuer: C = US, O = Internet Security Research Group, CN = ISRG Root X2
        Validity
            Not Before: Sep  4 00:00:00 2020 GMT
            Not After : Sep 17 16:00:00 2040 GMT