在 Centos 5 上，我尝试通过 HTTPS 下载，但收到证书错误：
$ curl https://nixos.org/nix/install
curl: (60) SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
More details here: http://curl.haxx.se/docs/sslcerts.html
...
这个问题有各种各样的答案（例如）表示要下载https://curl.haxx.se/ca/cacert.pem到/etc/pki/tls/certs/ca-bundle.crt。
在另一台机器上，我下载了https://curl.haxx.se/ca/cacert.pem并将其复制到 Centos5 机器上/etc/pki/tls/certs/ca-bundle.crt。
但是，我仍然收到同样的错误
$ curl https://nixos.org/nix/install
curl: (60) SSL certificate problem, verify that the CA cert is OK. Details:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
More details here: http://curl.haxx.se/docs/sslcerts.html
我是否遗漏了某个额外步骤？