Simply prepending an
apt command with
DEBIAN_FRONTEND=something does not persist after the single command to which it is applied.
DEBIAN_FRONTEND options are documented in the Section 7 manual pages of
debconf (you may need to install the
debconf-doc package in order to make these available on your system). From
man 7 debconf:
One of debconf's unique features is that the interface it presents to
you is only one of many, that can be swapped in at will. There are many
debconf frontends available:
dialog The default frontend, this uses the whiptail(1) or dialog(1)
programs to display questions to you. It works in text mode.
The most traditional frontend, this looks quite similar to how
Debian configuration always has been: a series of questions,
printed out at the console using plain text, and prompts done
using the readline library. It even supports tab completion. The
libterm-readline-gnu-perl package is strongly recommended if you
chose to use this frontend; the default readline module does not
support prompting with default values. At the minimum, you'll
need the perl-modules package installed to use this frontend.
This frontend has some special hotkeys. Pageup (or ctrl-u) will
go back to the previous question (if that is supported by the
package that is using debconf), and pagedown (or ctrl-v) will
skip forward to the next question.
This is the best frontend for remote admin work over a slow con‐
nection, or for those who are comfortable with unix.
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.
It also notes that:
You can change the default frontend debconf uses by reconfiguring deb‐
conf. On the other hand, if you just want to change the frontend for a
minute, you can set the DEBIAN_FRONTEND environment variable to the
name of the frontend to use. For example:
DEBIAN_FRONTEND=readline apt-get install slrn
The dpkg-reconfigure(8) and dpkg-preconfigure(8) commands also let you
pass --frontend= to them, followed by the frontend you want them to
Note that not all frontends will work in all circumstances. If a fron‐
tend fails to start up for some reason, debconf will print out a mes‐
sage explaining why, and fall back to the next-most similar frontend.