У apt-get есть -y, --yes, --assume-yes :
       Automatic yes to prompts; assume "yes" as answer to all prompts and
       run non-interactively. If an undesirable situation, such as
       changing a held package, trying to install a unauthenticated
       package or removing an essential package occurs then apt-get will
       abort. Configuration Item: APT::Get::Assume-Yes.
или, альтернативно, --force-yes :
       Force yes; this is a dangerous option that will cause apt to
       continue without prompting if it is doing something potentially
       harmful. It should not be used except in very special situations.
       Using force-yes can potentially destroy your system! Configuration
       Item: APT::Get::force-yes
http://manpages.ubuntu.com/manpages/utopic/man8/apt-get.8.html