Примеры Add-Apt-Repository и обновление Apt Cache

# Adds a repository into the file
add-apt-repository 'deb http://us.archive.ubuntu.com/ubuntu xenial main universe' 

# Removes a repository from the file
add-apt-repository -r 'deb http://us.archive.ubuntu.com/ubuntu xenial main universe'

# Updates the APT cache
apt-get update
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