Suppose we need to change the actual TTL to 65.
Open the terminal (Ctrl + Alt + T) , and one by one we enter commands:
sudo -s echo "net.ipv4.ip_default_ttl=65" >> /etc/sysctl.d/sysctl.conf
If you didn't get an error, restart the computer. If you get an error: no such file or directory. Then you need to create this file. By using this commands you can create a file and write there an information about TTL.
sudo -s touch /etc/sysctl.d/net.conf echo "net.ipv4.ip_default_ttl=65" >> /etc/sysctl.d/net.conf
Next, restart the computer and get the required TTL. You can check the result with the command:
If you are unable to achieve the result, please write in the comments and I will try to help.