［求助］更新无效

引用:

无法下载全部的软件库索引

A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ubuntu.csie.ntu.edu.tw intrepid Release: 下列签名无效： NODATA 1 NODATA 2
A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ubuntu.csie.ntu.edu.tw intrepid-updates Release: 下列签名无效： NODATA 1 NODATA 2
A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ubuntu.csie.ntu.edu.tw intrepid-backports Release: 下列签名无效： NODATA 1 NODATA 2
A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ubuntu.csie.ntu.edu.tw intrepid-security Release: 下列签名无效： NODATA 1 NODATA 2
A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ubuntu.csie.ntu.edu.tw intrepid-proposed Release: 下列签名无效： NODATA 1 NODATA 2
子进程 report-mirror-failure 返回了一个错误号 (1)Couldn't report problem to ''