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sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv C0A52C50

Relevant part hkp://xxx:80

title: APT - Error GPG Key category: Linux — When updating repository and get the error below, add the key based on last 8 characters:

Reading package lists... Done
W: GPG error: http://deb.opera.com stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F9A2F76A9D1A0061
W: You may want to run apt-get update to correct these problems


sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9D1A0061
sudo apt-get update

title: APT - Hash Mismatch category: Linux —

sudo rm -rf /var/lib/apt/lists/*
sudo apt clean
sudo apt update


  • https://askubuntu.com/questions/41605/trouble-downloading-packages-list-due-to-a-hash-sum-mismatch-error

    title: APT - Hold Unhold category: Linux —

    sudo apt-mark hold <package>
    sudo apt-mark unhold <package>

    title: APT - Old Ubuntu Repo category: Linux — To access old Ubuntu repositories, take a look at http://old-releases.ubuntu.com/

Edit etc/apt/sources.list and change CODENAME to your distribution’s code name, e.g. jaunty:

deb http://old-releases.ubuntu.com/ubuntu/ CODENAME main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-security main restricted universe multiverse
#deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-backports main restricted universe multiverse


  • http://superuser.com/questions/339537/where-can-i-get-the-repositories-for-old-ubuntu-versions

    title: APT - Timeout category: Linux —

    /etc/apt/apt.conf.d/99timeoutAcquire::http::Timeout "10";Acquire::ftp::Timeout "10";