将apt-get替换成 163源后执行apt-get update 提示
Err:1 http://mirrors.163.com/ubuntu bionic InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
Err:2 http://mirrors.163.com/ubuntu bionic-security InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
Err:3 http://mirrors.163.com/ubuntu bionic-updates InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
Err:4 http://mirrors.163.com/ubuntu bionic-proposed InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
Err:5 http://mirrors.163.com/ubuntu bionic-backports InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
Hit:6 https://deb.nodesource.com/node_12.x bullseye InRelease
Err:7 http://http.re4son-kernel.com/re4son kali-pi InRelease
Could not connect to http.re4son-kernel.com:80 (52.95.128.205), connection timed out
Reading package lists... Done
W: GPG error: http://mirrors.163.com/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://mirrors.163.com/ubuntu bionic InRelease' 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.
W: GPG error: http://mirrors.163.com/ubuntu bionic-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://mirrors.163.com/ubuntu bionic-security InRelease' 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.
W: GPG error: http://mirrors.163.com/ubuntu bionic-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://mirrors.163.com/ubuntu bionic-updates InRelease' 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.
W: GPG error: http://mirrors.163.com/ubuntu bionic-proposed InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://mirrors.163.com/ubuntu bionic-proposed InRelease' 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.
W: GPG error: http://mirrors.163.com/ubuntu bionic-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3B4FE6ACC0B21F32
E: The repository 'http://mirrors.163.com/ubuntu bionic-backports InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.解决方案：
sudo gpg --keyserver keyserver.ubuntu.com --recv 3B4FE6ACC0B21F32 #修改为提示的公钥
sudo gpg --export --armor 3B4FE6ACC0B21F32 | sudo apt-key add - #修改为提示的公钥上次更新时间 13 3 月, 2023 at 09:59 上午