Can’t boot because of trying to install LightDM

[pvasshep]

I have begun trying to upgrade from Mint 17 eventually to 19.1.

However, I started by trying to change the display manager to LightDM as I had found an instruction that this was necessary. But - this did not go well - and now my computer will not boot into Mint 17.

Luckily, I also have Mint 15 available on the same computer and was able to find the files for Mint 17. So I am looking for help to try to find what file I need to edit (and what to edit into the fie) to enable my Mint 17 to go back to using the old display manager.

I hope I have been clear and that someone can help me to get my computer back to where it was before I tried installing LightDM.

Thanks.
EDiT after initial post: I did not remove the original display manager though the instructions had said to do that because I was afraid the new one would not work. For one thing, I never saw any sign of something called”slick-greeter.” I did get to a point where I had the option to choose between MDM and LightDM and chose LightDM at that point. Then I tried rebooting and it failed to boot.


—Kathy. — who’s been dreading 2019 because I knew I would need to update my Mint 17....

[redlined]

hi Kathy!

this sounds really bad. Please post the link to the instructions you followed to replace MDM with LightDM, that might help other more experienced folks in our forums to help sort how to fix this, if possible. The upgrade path alone is a 'long day' sort of headache, from 17 to 17.3 to 18 to 18.3 to 19 to 19.1 if I recall correctly

Otherwise, if you have backups of personal files then a fresh install may be best option. If you have a separate /home directory in the LM17 install then selecting "Something else" during the LM19.1 install will allow you to set mount point for /home to the old partition where /home was and may help in minimizing your lost efforts in customizing LM17. Your personal files would be there, as well settings, however you'd have to reinstall apps regardless.

If you do not have backups but can access your LM17 install space then see what you can recover from that (to some external storage), even using LM19.1 live session from USB stick or cd/dvd may be a good way to get that done.

[smurphos]

Then I tried rebooting and it failed to boot.
—Kathy. — who’s been dreading 2019 because I knew I would need to update my Mint 17....

Hi Kathy, do you get a terminal like full screen interface when you attempt to boot with a login prompt? If so login with your normal credentials and run sudo apt purge lightdm && sudo apt install --reinstall mdm. You should get a prompt to accept mdm as your display manager. Once done use the command reboot to reboot.

If not how far do you get in the boot sequence and what's the end result?

If you are planning on attempting the upgrade path from 17 to 19 the time when the swap from MDM to lightDM is required is before the 18.3 > 19 step. But I'd suggest saving your self a lot of time and possible agro by backing up your personal data and making a fresh install.

[pvasshep]

Thanks for the comments. I decided to go ahead and back up old files and install 19.1. Install went fine. Now for trying to get it into some sort of shape similar to what I left behind... Thanks again. Though I'll still be on the lookout for a way to be able to fix the old 17 install as it's sitting there (alongside the new 19.1 and the old 15.)

[redlined]

Though I'll still be on the lookout for a way to be able to fix the old 17 install as it's sitting there (alongside the new 19.1 and the old 15.)

I do believe that is exactly what smurphos is working on in his reply this thread, so that part might get done quickly if troubleshooting there is continued. and fixing up 17 now may help save some of your work time in getting LM19.1 tweaked up the way you prefer things using old version of APTIK to backup from 17 if/when it gets back to functional, then restore backup in new install.