Ubuntu 18.10 OS has long been transferred, but only recently noticed that only 256MB of graphics memory is available, although when I was under windows there was 1GB (GeForce GT440), it turned out that I used the ubuntu open source driver, and then installed the proprietary driver nvidia. There were no errors during the installation process, but after rebooting, ubuntu simply did not load. I tried different installation methods: through the console, linux packages, the official driver installation program from the Nvidia website, but the problem persists. I also want to note that when I installed the drivers from the program from the Nvidia website, the problem, unlike other methods, arose during the installation process.
PS The startup problem is solved if you start the terminal from recovery mode and enter the command sudo apt-get purge nvidia-* (Remove all drivers from nvidia), then ubuntu will again start using open source drivers with 256mb memory