** Changed in: debconf (Debian)
Status: Unknown => New
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https://bugs.launchpad.net/bugs/1822270
Title:
Debconf readline frontend does not show options
Status in debconf package in Ubuntu:
Confirmed
Status in debconf source package in Xenial:
Confirmed
Status in debconf source package in Bionic:
Confirmed
Status in debconf source package in Cosmic:
Confirmed
Status in debconf source package in Disco:
Confirmed
Status in debconf source package in Eoan:
Confirmed
Status in debconf package in Debian:
New
Bug description:
[Impact]
debconf prompts the user for input before displaying options
[Description]
When upgrading packages with apt or dpkg, debconf scripts are ran through
'run-parts' with the '--report' flag. This causes script output to be handled
through pipes set up by run-parts, and buffers output from maintainer scripts
nicely for formatting.
If debconf makes use of the readline frontend, any prompts will bypass
the run-parts buffers and be displayed directly to /dev/tty. This
generally causes the prompt to be displayed before the user gets any
of the available options for it, and printing will block until the
user inputs a valid option.
[Test Case]
1) Deploy a VM through e.g. uvt-kvm
$ uvt-kvm create disco release=disco
2) Remove the whiptail package to force the readline frontend in debconf
root@disco:~# apt remove --purge whiptail -y
3) Install grub-legacy-ec2 and prepare /boot/grub/menu.lst for an upgrade
through run-parts
root@disco:~# apt update && apt install -y grub-legacy-ec2
root@disco:~# rm -f /boot/grub/menu.lst*
root@disco:~# touch -d "4 years ago" /boot/grub/menu.lst
4) Invoke run-parts as in a kernel upgrade (kernel version doesn't matter, we
just need it to think menu.lst needs an upgrade)
root@disco:~# run-parts --exit-on-error --arg=5.0.0 /etc/kernel/postinst.d
--report
...
/etc/kernel/postinst.d/x-grub-legacy-ec2:
debconf: unable to initialize frontend: Dialog
debconf: (No usable dialog-like program is installed, so the dialog based
frontend cannot be used. at /usr/share/perl5/Debconf/FrontEnd/Dialog.pm line
76.)
debconf: falling back to frontend: Readline
Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst
Searching for splash image ... none found, skipping ...
What would you like to do about menu.lst?
The "What would you like to do about menu.lst?" prompt will block
until the user enter a valid option, even though it's being displayed
before the available options.
[Regression Potential]
We could hit regressions if changing debconf's printing to /dev/tty is
expected by other programs. The changes are needed only in the readline
frontend, so that would minimize impact of any possible regressions. The fixes
will be thoroughly tested with autopkgtest and use-case scenarios.
# # # #
[Original Description]
When upgrading the kernel on a recent Bionic minimal image, the user is
prompted to resolve a conflict in the file /boot/grub/menu.lst.
The minimal images do not have dialog/whiptail installed, so debconf
falls back to using the readline frontend.
The user sees the prompt: "What would you like to do about menu.lst?"
but is not presented with the list of options to choose from.
If a valid option is typed in, debconf will continue processing
correctly and the list of options appears on the screen. See also
https://pastebin.ubuntu.com/p/8xvSn88SKG/
STEPS TO REPRODUCE:
Launch the minimal Bionic image with serial 20190212 http://cloud-
images.ubuntu.com/minimal/releases/bionic/release-20190212/ubuntu-18.04
-minimal-cloudimg-amd64.img
for example via multipass and run `apt-get update` and `apt-get dist-
upgrade`.
To manage notifications about this bug go to:
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