我有两年未升级的 ubuntu 12.04 服务器。在我们决定升级它之前，它一直运行良好。
升级（apt-get upgrade）后，CA 文件/usr/share/ca-certificates/mozilla/Entrust.net_Secure_Server_CA.crt消失，程序无法访问Entrust Certification Authority - L1C.
知道为什么会这样吗？
这是日志：
ubuntu@ip-10-67-192-40:~$ curl -i https://api.demo.com/ #works
ubuntu@ip-10-67-192-40:~$ file /etc/ssl/certs/5f267794.0
/etc/ssl/certs/5f267794.0: symbolic link to `Entrust.net_Secure_Server_CA.pem'
ubuntu@ip-10-67-192-40:~$ file /etc/ssl/certs/Entrust.net_Secure_Server_CA.pem
/etc/ssl/certs/Entrust.net_Secure_Server_CA.pem: symbolic link to `/usr/share/ca-certificates/mozilla/Entrust.net_Secure_Server_CA.crt'
ubuntu@ip-10-67-192-40:~$ file /usr/share/ca-certificates/mozilla/Entrust.net_Secure_Server_CA.crt
/usr/share/ca-certificates/mozilla/Entrust.net_Secure_Server_CA.crt: PEM certificate
ubuntu@ip-10-67-192-40:~$ sudo update-ca-certificates
Updating certificates in /etc/ssl/certs... 0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d....done.
root@ip-10-67-192-40:~# apt-get update; apt-get upgrade
ubuntu@ip-10-67-192-40:~$ curl -i https://api.demo.com/ #dosen't work