我知道之前已经被问过很多次了，但这些解决方案都没有帮助我。
每次我运行时sudo apt upgrade都会出现此错误。
dpkg: error processing package systemd (--configure):
installed systemd package post-installation script subprocess returned error exit status 127
Errors were encountered while processing:
systemd
E: Sub-process /usr/bin/dpkg returned an error code (1)
并sudo dpkg --configure -a返回
Setting up udev (237-3ubuntu10.28) ...
/var/lib/dpkg/info/udev.postinst: 108: /var/lib/dpkg/info/udev.postinst: addgroup: not found
dpkg: error processing package udev (--configure):
installed udev package post-installation script subprocess returned error exit status 127
Setting up systemd (237-3ubuntu10.28) ...
/var/lib/dpkg/info/systemd.postinst: 123: /var/lib/dpkg/info/systemd.postinst: addgroup: …所以有两个PPA在期间引起GPG警告sudo apt update
W: GPG error: https://brave-browser-apt-release.s3.brave.com bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 4FE13824E3FFC656
E: The repository 'https://brave-browser-apt-release.s3.brave.com 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://repository.spotify.com stable InRelease: The following signatures couldn't be verified because the public key is not available: …