1. Modifying the hosts file manually
nano /etc/hosts as root/with sudo.
When you’ve got it open, paste the following at the bottom:
184.108.40.206 osu.ppy.sh c.ppy.sh c1.ppy.sh c2.ppy.sh c3.ppy.sh c4.ppy.sh c5.ppy.sh c6.ppy.sh ce.ppy.sh a.ppy.sh s.ppy.sh i.ppy.sh
CTRL+X and then Enter to save the file.
2. Installing the certificate
Download the certificate by clicking here
Open the Internet Explorer configuration by running
Double click the Internet Settings icon, navigate to the Content tab, then click the Certificates… button.
Click on Import, then Next.
Click Browse… then select the Gatari certificate.
Select Place all certificates in the following store, and click Browse.
Select Trusted Root Certification Authorities, and click Ok.
Click Next, Finish.
You should get a message saying The import was successful.
After that is done, you can start the client up, and log in with your Gatari credentials.