=== Allow third-party repositories when upgrading between distributions ===

Place:

{{{
[Sources]
AllowThirdParty=yes
}}}

into /etc/update-manager/release-upgrades.d/allow-third-party.cfg. From [[https://bugs.launchpad.net/ubuntu/+source/update-manager-core/+bug/147080|bug #147080: do-release-upgrade should make disabling third party repositories optional]].

=== Import an Ubuntu PPA key ===

Import an Ubuntu PPA key directly from the keyserver with:

{{{#!highlight sh
key=0x1111
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys $key
}}}

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CategoryCheatSheet