I recently upgraded to Lubuntu 18.04 from 17.10 on a machine that does not have a lot of hard drive space. The upgrade was very smooth -- not a glitch. But post-installation I lost close to 1GB of space, maybe a bit more. Just wondering if that is to be expected, if the new version is simply bigger. And if that is not it, what is causing it? I'm relatively new to linux. Thank you.
It's not anywhere near 1 GB larger. In fact, since the Lubuntu 18.04 installer ISO is about 1 GB, it might be hanging on to the package installer files it downloaded while you were upgrading your system.
You can try cleaning up APT packages and package installer files which might not be needed anymore by opening a terminal (press Ctrl+Alt+T) and running:
sudo apt autoremove --purge sudo apt clean
It is obvious that the 18.04 is larger than the 17.10 and this is because the newest release (18.04) comes with more features.
Also the 18.04 requirements (CPU, RAM and Memory) are higher than Lubuntu 17.10.
Also, the OS size or memory grows up with the tools you install.
So to sum up, 18.04 is larger than 17.10 but it is not remarkable difference. And in general, the more packages and tools you install, the larger gets your OS.
You can free some space by running, on the terminal :
sudo apt-get clean
sudo apt-get autoremove