好的，通常我每天运行一次 apt-get 更新和升级。现在突然它告诉我这个：
Fetched 666 B in 6s (105 B/s)
W: GPG error: ttp://archive.canonical.com oneiric Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: ttp://extras.ubuntu.com oneiric Release: The following signatures were invalid: BADSIG 16126D3A3E5C1192 Ubuntu Extras Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: GPG error: ttp://gb.archive.ubuntu.com oneiric …