I am writing a script for a unattended install of a package that is in our repo, it is a software package with one of Debian's marked config files. Is there any option that I can pass to apt-get/aptitude so that it accepts the new config files?

Basically I need an apt/aptitude equivalent of dpkg --force-confnew

I need to answer the following question posed while apt-get is installing with a Y

Configuration file ``/opt/application/conf/XXX.conf`'

==> File on system created by you or by a script.
==> File also in package provided by package maintainer.

What would you like to do about it ?  Your options are:
Y or I  : install the package maintainer's version
N or O  : keep your currently-installed version
  D     : show the differences between the versions
  Z     : background this process to examine the 

The default action is to keep your current version.

Additional Info:

Also, I am passing the sudo password in a pipe to execute the command

echo "mysudopass"|sudo -S apt-get mypackage

This is flagging an error in installation when the installation is at the config interactive phase.

I am on Ubuntu 10.04
apt version: apt

Why I cannot use dpkg: These Debians are to be installed from Repo and I don't have local Debians on my machine


4 Answers 4


You can pass dpkg parameters to apt-get like this

apt-get -y -o Dpkg::Options::=--force-confdef -o Dpkg::Options::=--force-confnew install pkgname1 pkgname2 ...

With --force-confdef if old config files still exist, they won't get overridden. So you probably won't use it, I'm just documenting it for others.

sudo will not ask for a password if you negate the authenticate option for the user or add the NOPASSWD tag in the specific entry. e.g.

someuser ALL = NOPASSWD: /usr/bin/apt-get

You could try the following:

export DEBIAN_FRONTEND=noninteractive
apt-get -q -y install whatever-2

But note that this has implications, like empty default passwords (maybe you'd like some deployment/config tool like puppet, chef, fabric...?).

See sudoers(5) about how to allow password-less sudo invocations.


In addition to the other answers, you may also have to set the environment UCF_FORCE_CONFFNEW=1.

E.g. openssh in debian stretch uses ucf (not debconf) in it's openssh-server/openssh-7.4p1/debian/openssh-server.postinst to ask about the config file. (You can see the openssh-server.postinst by using dget against http://security.debian.org/debian-security/pool/updates/main/o/openssh/openssh_7.4p1-10+deb9u4.dsc)

We've had to use all the tricks on this page in addition to being liberal users of debconf preseeding.

We did however stop just short of export DEBIAN_FRONTEND=noninteractive because we want to know if we missed something (that could be important). Our use case is an operator starting the operation. The upgrade is expected to be non-interactive, but the operator is present if something goes wrong and a dialog presents itself. Your situation may be different.

But export DEBIAN_FRONTEND=noninteractive is your proverbial sledgehammer.

Just beware: Setting -o Dpkg::Options::=--force-confnew and/or UCF_FORCE_CONFFNEW=1 means that all config files from installed packages revert to the upstream ones. So e.g. in the case of openssh-server, your /etc/ssh/sshd_config will be reset to factory settings. And e.g. PermitRootLogin=yes will be removed. But of course you don't use that, so you'll be fine! ;-)

  • The default value of PermitRootLogin is yes though. Nov 5, 2023 at 10:25

Alternatively to what forcefsck suggested I suggest you add this into APT settings so you are not required to add these hard-to-write options all the time. Also, this would be helpful for unattended upgrades if you have these setup.

Create /etc/apt/apt.conf.d/71debconf file to have the following content:

Dpkg::Options {

Note (from Geoff): this change would be a global change. If you have other packages on the system that you want to get unattended upgrades but have also manually configured, this would not be the appropriate solution.

  • This may be a good option, however it's important to note that this would be a GLOBAL change. If you have other packages on the system that you want to get unattended upgrades but have also configured, this would not be the appropriate solution.
    – Zefira
    Oct 17, 2018 at 1:45

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