some hosts don't have a sources.list at all

howto/upgrades/bullseye.md

@@ -96,8 +96,8 @@ bullseye procedure.
     auto-upgrades, and download packages:
 
         systemctl stop apt-daily.timer &&
-        sed -i 's#buster/updates#bullseye-security#' /etc/apt/sources.list $(ls /etc/apt/sources.list.d/*) &&
-        sed -i 's/buster/bullseye/g' /etc/apt/sources.list $(ls /etc/apt/sources.list.d/*) &&
+        sed -i 's#buster/updates#bullseye-security#' $(ls /etc/apt/sources.list /etc/apt/sources.list.d/*) &&
+        sed -i 's/buster/bullseye/g' $(ls /etc/apt/sources.list /etc/apt/sources.list.d/*) &&
         apt update &&
         ( apt -o APT::Get::Trivial-Only=true dist-upgrade || true ) &&
         df -h &&