Comment 6 for bug 40684

/var/lib/dpkg/info/passwd.config includes these lines:

    if ! root_password; then
     sudoers_admin_group
     addgroup --system admin >/dev/null 2>&1 || true
     adduser "$USER" admin >/dev/null 2>&1 || true
    fi

basically, if you've set a root password, then it won't make the 'admin' group, or allow the admin group to use sudo to become root.

This in turn makes the GNOME menu entries for 'synaptic' and other admin programs not work, since they use 'gksudo'.

Do you have references for the other bugs where this has been brought up? This bug should be marked as a duplicate of them.