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# Add the repository key
curl -sL https://deb.xengi.de/key.asc | gpg --dearmor > /usr/share/keyrings/xengi-archive-keyring.gpg
# Add the repository
mkdir -p /etc/apt/sources.list.d
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/xengi-archive-keyring.gpg] https://deb.xengi.de stable main" > /etc/apt/sources.list.d/xengi.list
# Install repository keyring
apt update
apt install xengi-archive-keyring