It's a bit technical, but what I'd do in your situation is boot off the install CD and then open a terminal and chroot into the hard drive's install. Then, anything run inside the terminal will act as if it was booted off the hard drive and you can run your fix-ups.

Gentoo Linux has good guides [url=https://wiki.gentoo.org/wiki/Project:X86/Chroot_Guide][2], so here are the relevant bits adapted for you:

1. Boot off your installation CD into the desktop

2. Choose/make a folder to mount your hard drive at, if the CD hasn't already. (something like /mnt/chroot)
3. Mount your hard drive to the folder you created (something like "sudo mount /dev/sda1 /mnt/chroot" where the /dev/sda1 part can be identified in the partitioning utility in the system utilities section of the launcher menu.)

4. Open up a terminal

5. Run these commands to give the chroot access to the various kernel interfaces that normally get set up for it on boot:

sudo mount --rbind /dev /mnt/chroot/dev
sudo mount -t proc /proc /mnt/chroot/proc
sudo mount --rbind /sys /mnt/chroot/sys
sudo cp /etc/resolv.conf /mnt/chroot/etc

6. Run these commands to switch into the chroot

sudo chroot /mnt/chroot /bin/bash
source /etc/profile
export PS1="(chroot) $PS1"

(The last one just changes the prompt so you can easily see whether the terminal is in the chroot)

7. Use the chrooted terminal to run whatever commands you need to in order to fix up your hard drive-installed copy.

Since you're on MINT, which descends from Debian, once you've got everything else fixed up, you should be able to fix GRUB by running "sudo update-grub" in the chrooted terminal.

NOTE: If you want to run GUI apps in the chroot, you'll need to copy the ~/.Xauthority and ~/.xauth* files from the CD desktop's $HOME to the chroot's $HOME and then run "export DISPLAY=:0.0" or the chrooted apps will get an "access denied" when they try to connect to the GUI server.

Worst case scenario, one trick I've used in the past to recover a totally messed up system was:

1. Boot off the install CD into the desktop
2. Delete every folder on the hard drive except "/home".
3. Rename "/home" to "/home.old"
4. (optional, but recommended) Stick in a thumbdrive and copy "/home.old" to it as a backup
5. Start the install process, choose advanced partitioning, and, rather than changing anything, just set the mount points and make sure "format" is unchecked.
6. When it asks for a username, enter your old one.
7. When the installation finishes, before you restart, replace /home/your_username on the hard drive with /home.old/your_username
8. Reboot and reinstall any non-default packages you had before.

(If you want to get advanced, it's possible to chroot into the hard drive and dump a list of installed packages which can then be restored automatically [url=https://askubuntu.com/questions/9135/how-to-backup-settings-and-list-of-installed-packages][2] after the reinstall is finished.)

Yes, both of these could be considered somewhat "nuclear options" by some people, but they apply generally... and I prefer to know one solution that I can use everywhere, rather than a handful of things I learn once and then never use again.

are you sure it's not hardware related ? ie harddisk just died, then the BIOS will simply boot from the next available harddisk ...
that would be my first guess, since there are relatively few things that could go wrong during an update that would simply kill your boot loader.
so check in BIOS that the hdd is still there and set to as first boot medium

I agree with immi101, it sounds a lot like the HDD may have died. The only time I've encountered that error trying to install/update packages has been when package installation was previously interrupted due to power loss or so, and in that case it wouldn't even begin trying to install anything until it had been sorted out. Also it's very unlikely that GRUB would have been affected by the installation of any other packages.

Disk failure would explain the "file lock" error suddenly occurring mid-install, the sudden unresponsiveness of the launcher menu/desktop, and if GRUB was on the same HDD then it would also explain why the GRUB menu isn't showing up any more.

Yep, that was my first thought about it as well. Looks very much like disk failure. Was it an SSD?

For all those who got this error:

PANIC
Initial setup failed. Cannot continue.

Error: Couldn't run mojosetup

It probably means that your installation wasn't fully finished donwloading.
If like you have unstable connection , you can download file with free DownThemAll! addon (Firefox).
You can pause and resume downloads at any time.

For the record, Firefox 56 will be the last version of Firefox which works with DownThemAll.

With the release of Firefox 57, the browser will only load Chrome-style extensions and, so far, they've shown no interest in adding APIs to allow extensions the raw filesystem access necessary for DTA-style extensions. The author of DTA has very publicly expressed his decision to let DTA die with the old extension API.

The two alternative approaches are or copying your GOG login cookies into a [url=https://gist.github.com/ssokolow/2fb8debc7dfdbf1d9a0da90284f5d73a#downthemall-successor]standalone download manager.

On Linux, every bit of "personal customization" except your list of installed packages is stored in your homedir... so the easiest way to reinstall while preserving your settings is to backup and then restore your home directory and, optionally, your list of installed packages.

In every distro installer I've tried, if you choose not to format the drive, it'll leave the existing contents untouched, so the instructions I gave are a trick for transferring your home directory from an old to a new installation without having to copy them to another drive and then back again. (And, as everyone's probably noticed, moving files within the same drive is instantaneous because it's just renaming.)

So, you...

1. Delete everything where a package installation mistake might be lurking (the stuff that isn't specific to a single user)
2. Move /home/your_username so there's no risk of your dotfiles getting overwritten
3. Reinstall without formatting
4. Replace the fresh and empty /home/your_username with the one you renamed.

I actually used this approach to switch from a broken Gentoo install to a fresh Lubuntu install when I didn't have time to diagnose the problem or reinstall Gentoo from scratch.

...but, as I cautioned, make a backup to a thumbdrive anyway.

If the problem persists after that, it's either hardware or inside your homedir. In the latter case, just create a new profile and move the old profile to /home/your_username/home.old to be picked apart at your leisure.

Also, considering how GOG installs games to the /home by default, you save a lot, or even A LOT, of time as compared to doing the equivalent on Windows.

fsck / badblocks
see this guide for more details:
https://mintguide.org/system/283-how-to-check-and-fix-the-disk-for-errors-and-bad-sectors-in-linux-mint.html

but if you can still access the disk from the live cd then there is still hope that it wasn't a hardware fault but simply some weird error. it happens ;)
here is another link describing how to restore grub from a mint liveCD
https://community.linuxmint.com/tutorial/view/2283

for the future you can also take a look at smartmontools (and gsmartcontrol for a nice GUI) which allows you to view the "health" data of your harddisk which usually gives you an advanced warning about impending disk failures due to old age.

Hello I just installed warsow to see if gog works on linux mint - it installed but wont launch, anyone know what's up? Im running latest version of linux mint

Did you gave it permission to execute?

You're probably just missing some dependencies... the store page for Warsow says: Requires the following packages to be installed: libsdl2-2.0-0

I picked up Quake 3 for the assets to run on Linux. I installed the assets with the 'game-data-packager' utility after extracting the GOG installer with Innoextract. Game loads up fine and the single player works, but I keep getting an "INVALID GAME FOLDER" error whenever I try to load up the game. Any idea what I did wrong?

Xubuntu 17.04
RX 480 with the Padoka PPA drivers

I'm not sure if this is the best place, but here is my problem:

Two games, Vampire - The Masquerade - Bloodlines and Fallout New Vegas, fail to install on Linux through Wine and PlayOnLinux. The installer can't locate its data files, even after asking for their location. So, I'm unable to install these games the way I usually do. I think these are the new Galaxy installers, and I'm not happy that they are already causing issues.
I know GOG doesn't officially support this method, but it's the way I play most of the games purchased here. I need it solved!