Problem
You removed a package by force from the command line. Using the --purge option removed the file and it's dependencies were caught by autoremove. This combination together purges the named package and all it's dependencies, plus all the configuration data.
Resolution
We need to determine the list of packages that the package we removed depends on, like so (this list is from a XUbuntu install, but the result will be nearly identical, as Ubuntu is a Debian fork):
sudo -i apt-cache depends synaptic synaptic Depends: libapt-inst2.0 Depends: libapt-pkg5.0 Depends: libc6 Depends: libept1.5.0 Depends: libgcc1 Depends: libgdk-pixbuf2.0-0 Depends: libglib2.0-0 Depends: libgtk-3-0 Depends: libpango-1.0-0 Depends: libstdc++6 Depends: libvte-2.91-0 Depends: libx11-6 Depends: libxapian30 Depends: hicolor-icon-theme Depends: policykit-1 policykit-1:i386 Conflicts: menu Recommends: libgtk2-perl Recommends: rarian-compat Recommends: xdg-utils Suggests: dwww Suggests: menu menu:i386 Suggests: deborphan Suggests: apt-xapian-index Suggests: tasksel Suggests: software-properties-gtk
In your case, from your Edit(I've edited your question to highlight the error), we determined that the missing package is: libept1.5.0, listed as libept1.5.0 (1.1+nmu3 and others) in the Debian Stretch Package Repository.
We must now download the missing package from the repository, by visiting Package: libept1.5.0 (1.1+nmu3 and others): High-level library for managing Debian package information. Scroll down to the bottom of the window, and download the package appropriate for your architecture. Ignore the note on the resulting page, as we tried that first.
After saving the package, start a new terminal window, and cd /path/to/downloaded/file. Issue sudo dpkg -i libept1.5.0_1.1+nmu3+b1_<arch>.deb to install the package.
Extra Credit
Use CAUTION if attempting this: I'm offering this because the package we downloaded should be in your repository. Since I have no idea what state your repositories and list are in, I'm starting from scratch.
Taken from How do I restore the default repositories? over at AskUbuntu, but the concept is the same. There is a sources.list generator for Debian at Debian Sources List Generator.
- Install the packages required by the Generator:
apt-get install curl wget apt-transport-https dirmngr - Remove your sources list, by issuing:
sudo rm /etc/apt/sources.list - Configure the options etc, most importantly, choose the Proper Version. Once the version is chosen, choose any third party mirrors if desired.
- Click Generate.
- Use some form of sudo, i.e.
gksudoto open your chosen text editor. You need to be root to save the result in the /etc/ directory. - Copy the results of step 4 into the editor in step 5. If you chose any third party repositories, don't forget to issue the commands in the GPG Keys output window.
- Save the result as
sources.list in /etc/apt/ - Issue a
sudo apt-get update
Example Output from Generator
#------------------------------------------------------------------------------# # OFFICIAL DEBIAN REPOS #------------------------------------------------------------------------------# ###### Debian Main Repos deb http://deb.debian.org/debian/ stable main contrib non-free deb-src http://deb.debian.org/debian/ stable main contrib non-free deb http://deb.debian.org/debian/ stable-updates main contrib non-free deb-src http://deb.debian.org/debian/ stable-updates main contrib non-free deb http://deb.debian.org/debian-security stable/updates main deb-src http://deb.debian.org/debian-security stable/updates main deb http://ftp.debian.org/debian jessie-backports main deb-src http://ftp.debian.org/debian jessie-backports main
Package 'synaptic' is not installed, so not removed 0 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.Please try again after the 9 are upgraded. Usesudo -ifollowed byapt-get update && apt-get upgradeapt-get updateprior to this - but upgrading didn't didn't help either. Now it says0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.and I still get the same messages when trying to install synaptic. I guess I need to upgrade these 2 packages as well to get it working? I don't know which of the packages those are and why they're having problems though.The following packages have been kept back: firefox-esr firefox-esr-l10n-d. I just restarted my PC and did not start up firefox and it still didn't work.--purgeremoved libept which was a dependency for synaptic. Then purge firefox, and download the newest version for Debiansudo apt-get --purge autoremove firefox-esrandsudo apt-get install firefox-esrright? Would that delete my session and all my settings etc? Or would they be kept? Should I do the same for libept afterwards?