Ubuntu – How to install apt packages non-interactively

aptpostfix

If I run:

sudo apt-get --yes install postfix

or

sudo bash -c 'yes | apt-get --yes install postfix'

an interactive prompt appears to configure postfix. I need to automate the installation of postfix (I can modify the configuration files after the install).

Is there some magic that lets me install postfix (and other package) without human intervention?

Best Answer

Set the DEBIAN_FRONTEND to noninteractive:

DEBIAN_FRONTEND=noninteractive apt-get ...

This is also applicable to dpkg --reconfigure, dpkg-configure, etc.

From man 7 debconf:

noninteractive
      This  is  the anti-frontend. It never interacts with you at all,
      and makes the default answers be  used  for  all  questions.  It
      might  mail  error messages to root, but that's it; otherwise it
      is completely silent and unobtrusive,  a  perfect  frontend  for
      automatic installs. If you are using this front-end, and require
      non-default answers to questions, you will need to  preseed  the
      debconf  database;  see  the section below on Unattended Package
      Installation for more details.

If you do set noninteractive, you should consider answering debconf questions by using debconf-set-selections.

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