Use curl to access a URL protected by Kerberos HTTP SPNEGO

To access a URL protected by Kerberos HTTP SPNEGO, ensure that your version of curl supports GSS and is capable of running curl -V.

Run curl -V.

$ curl -V
curl 7.19.7 (universal-apple-darwin10.0) libcurl/7.19.7 OpenSSL/0.9.8l
zlib/1.2.3
Protocols: tftp ftp telnet dict ldap http file https ftps
Features: GSS-Negotiate IPv6 Largefile NTLM SSL libz

Log on to the KDC using kinit.

$ kinit
Please enter the password for username@LOCALHOST:

Use curl to fetch the protected URL.
```
$ curl --cacert
              /path/to/truststore.pem --negotiate -u : -b ~/cookiejar.txt -c ~/cookiejar.txt https://localhost:14000/webhdfs/v1/?op=liststatus
```
where:
- The --cacert option is required if you are using TLS/SSL certificates that curl does not recognize by default.
- The --negotiate option enables SPNEGO in curl.
- The -u: option is required but the username is ignored (the principal that has been specified for kinit is used).
- The -b and -c options are used to store and send HTTP cookies.
- Cloudera does not recommend using the -k or --insecure option as it turns off curl's ability to verify the certificate.