curl 無法獲取本地頒發者證書

我正在使用Let’s Encrypt證書，即使當我使用瀏覽器訪問伺服器時，瀏覽器報告頁面是“安全的”，但是當我使用它時我得到了關注curl。

# curl https://X.X.X
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: http://curl.haxx.se/docs/sslcerts.html

curl performs SSL certificate verification by default, using a "bundle"
of Certificate Authority (CA) public keys (CA certs). If the default
bundle file isn't adequate, you can specify an alternate file
using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
the -k (or --insecure) option.
# 

我的系統：

# cat /etc/debian_version 
8.7
# cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
# 

我只使用privkey.pem&cert.pem作為我的 fqdn.pem，現在fullchain.pem也使用菊花鏈。

使固定：

# cat privkey.pem cert.pem fullchain.pem > ~/fqdn.pem
#

curl:

# curl -I https://X.X.X
HTTP/1.1 401 Unauthorized
Server: nginx/1.11.12
Date: Mon, 03 Apr 2017 16:56:33 GMT
Content-Type: text/html
Content-Length: 196
Connection: keep-alive
WWW-Authenticate: Basic realm=""

# 

引用自：https://serverfault.com/questions/842280