我使用了这里给出的所有答案：“GPG 错误：发布：以下签名无效：BADSIG”
但我仍然每次都遇到同样的错误：
Reading package lists... Done
W: GPG error: http://archive.canonical.com precise Release:
The following signatures were invalid: 630239CC130E1A7FD81A27B140976EAF437D05B5
E: The repository 'http://archive.canonical.com precise Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore
disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
第一次尝试：
ahadji05@ahadji05-UX330UAR:~$ gpg --keyserver keyserver.ubuntu.com --recv-keys 16126D3A3E5C1192
gpg: key 16126D3A3E5C1192: 3 signatures not checked due to missing keys
gpg: key 16126D3A3E5C1192: public key "Ubuntu …