> > The Debian English-language backports wiki FAQ suggests (to find > all backported packages on a given machine): > > https://backports.debian.org/FAQ/ >
I removed all backported packages. Then did apt-get autoremove. Then removed the jessie-backports line from sources.list. I appear to have come back to my original system. However I am now getting an error on apt update. W: http://security.debian.org/debian-security/dists/stretch/updates/InR elease: The key(s) in the keyring /etc/apt/trusted.gpg are ignored as the file is not readable by user '_apt' executing apt-key. W: http://ftp.us.debian.org/debian/dists/stretch-updates/InRelease: The key(s) in the keyring /etc/apt/trusted.gpg are ignored as the file is not readable by user '_apt' executing apt-key. W: http://ftp.us.debian.org/debian/dists/stretch/Release.gpg: The key(s) in the keyring /etc/apt/trusted.gpg are ignored as the file is not readable by user '_apt' executing apt-key. Any help on that? thanks!
