Every app in my Xubuntu 18.04 deleted by Tasksel. Please Help

I tried to remove samba-server with this command (sudo tasksel remove samba-server) and every app even the system apps are deleted and now xubuntu is stuck at boot, just showing loading. What should I do?

Did tasksel deleted my files too?

TL;DR - it is a serious bug, do not use tasksel for removing things!

Analysis

Below is available options of tasksel:

$ tasksel --help
Unknown option: help
Usage:
tasksel install <task>...
tasksel remove <task>...
tasksel [options]
    -t, --test          test mode; don't really do anything
        --new-install   automatically install some tasks
        --list-tasks    list tasks that would be displayed and exit
        --task-packages list available packages in a task
        --task-desc     returns the description of a task

Samba task is named as samba-server as you wrote:

$ tasksel --list-tasks | grep -i Samba
u samba-server  Samba file server

It consists of only one package:

$ tasksel --task-packages samba-server
samba-server^

If we try to simulate uninstall - we get the following line:

$ sudo tasksel --test remove samba-server
debconf-apt-progress -- apt-get -q -y \
-o APT::Install-Recommends=true \
-o APT::Get::AutomaticRemove=true -o APT::Acquire::Retries=3 \ 
install samba-server^-

(in the line above the last hyphen - cause problems).

What I did:

1. Booted Ubuntu 18.04 LTS clean VM, installed tasksel with sudo apt-get install tasksel
2. Installed Samba with sudo tasksel install samba-server
3. Ran sudo tasksel remove samba-server
4. Rebooted and got broken system on next boot

Fix the system

Then I tried to repair the system:

1. We need to boot in Recovery mode (click Shift on boot, in GRUB select Advanced options for Ubuntu, select Ubuntu, with Linux ... (recovery mode))

2. Select resume Resume normal boot to access login shell

3. Open first console #1 with Ctrl+Alt+1 then login

4. If you do not have internet - check Ethernet interface name and run DHCP-client manually on it:

   ifconfig -a # got enp0s3
   sudo dhclient enp0s3
   

5. Reinstall xubuntu-desktop meta-package to the system:

   sudo apt-get install xubuntu-desktop
   

6. After reboot I can access the system.

Conclusion

So it seems that it is a serious bug - I have found some with almost same symptoms:

• bug 574287 reported on on 2010-05-03 - "tasksel: forcefully removes packages when tasks overlap"
• bug 1338223 reported on 2014-07-06 - "Tasksel has deleted all my data!".

Also I have filed new bug 1779645 "Critical bug in tasksel: tasksel remove task-name removes whole system"

What to do?

Do not use tasksel for removing things at least on 16.04 LTS, 18.04 LTS and 20.04 LTS.