This guide supposes you are familiar with using the Linux terminal.

DemonCrawl does not work out of the box on Ubuntu 18.04 LTS. No error message, you need to run it in command line in order to get the error message to pop up.

To do so :
Right click on DemonCrawl in your Steam library -> Local Files -> Browse Local Files.
Then, once you get the folder: right click -> Run in Terminal.

From there, if you type :

./demoncrawl

You will get the error :

./demoncrawl: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.29' not found (required by ./demoncrawl)

This is because Ubuntu 18.04 LTS does not have such a version of the glibc yet. From there, you have two choices.. Either upgrading Ubuntu to the latest non-LTS version. I think 19.04 should work fine. Or you install the glibc manually!

It's not that scary.

Place yourself in a dedicated folder of your choice, like ~/Documents/install, to run :

mkdir -p ~/Documents/install
cd ~/Documents/install
# Run the below command without the space between the two slashes /
git clone git:/ /sourceware.org/git/glibc.git

Once you have cloned the Glibc git repository, run the following commands :

cd glibc
mkdir build
cd build
../configure --prefix=/tools # VERY IMPORTANT: do not forget the --prefix=/tools

The --prefix=/tools ensures the glibc will not overwrite your existing one, by installing it on a new directory (here, /tools)! This is very important, because since Ubuntu 18.04 does not officially support such a glibc version, you might run into big troubles if you overwrite your current glibc version. The kind of trouble that could make you have to reinstall your entire OS. So do not forget this option ;)

The configure might fail because of missing libraries. Install the missing libraries - for me, I had to install bison, so a simple `apt-get install bison` did the trick.

Once the configure phase is done, it's time to build, and then install :

make -j3 # Replace 3 by the number of cores you have
sudo make install

Now, you have installed the newest Glibc on your system - congratulations!

However, DemonCrawl will still use the default one - the older.

To make it use the newest one, you need to start DemonCrawl in the command line with the following:

LD_PRELOAD=/tools/lib/libm.so.6 ./demoncrawl

This still failed on my system, because it needed libsteam_api.so to be in /usr/lib ; so you likely have to run the following command too, from within the DemonCrawl folder :

sudo cp libsteam_api.so /usr/lib

Once you've done that one last command, the LD_PRELOAD command should run like a charm.

But it can be a bit tiring to always have to go to the command line to start the game. So you can edit run.sh instead - edit the last line so that it now contains :

LD_PRELOAD=/tools/lib/libm.so.6 ./demoncrawl

And now, it should work like a charm when starting from Steam as well :)

I wrote this guide very fast - I hope it will be useful to you. I haven't made it particularly user friendly so if you have any question don't hesitate, I will do my best to reply to you and maybe help you too.

Happy mining!