Minecraft server: How do I turn the server back on & how do I update versions??

Hi there!
Recently I used the Linode marketplace to create a Minecraft java server. I modified several files and needed to reboot the server to commit the changes. I pressed the "reboot" button on my Linode, and after it was up and running again, I couldn't connect to the server.
Does anyone know how to start the server back up?
Also, do I just need to run java -Xmx1024M -Xms1024M -jar minecraft_server.jar nogui or do I have to run a script like start.sh? Do I need to run a program like screen to make it run 24/7?
My second question is how to update the Minecraft server, e.g. If I used 1.18 and wanted to migrate it to 1.18.1 (I don't need to migrate right now, Just need to know for the future.)
Hope someone can help, Thanks!