All Questions(ubuntu)

I recently set up a machine with Ubuntu Server to host game servers. I installed a backup plugin for each game server that creates frequent backups of game world files in a particular folder on the machine. I also established a cron task to automatically copy those backups to my Dropbox folder every night using rsync with the -a option.

After a few months my Dropbox account reached its storage limit and I realized I would not be able to keep so many backups, so I configured the game server backup plugin to not retain so many backups, then waited a few days to see if it would delete the older backups as it is scheduled to do on a weekly basis. The backup plugin eventually did its job and deleted the older backups, so I was expecting the rsync cron task to subsequently delete the older backups from my Dropbox folder to match the source folder, but it has not done so. So I have a couple of questions:

• By default, does rsync only add files to the destination folder that have been added to the source folder and change files that have been changed in the source folder but NOT delete files that were deleted from the source folder?

• If that is the case, what is the best way to make rsync do this? I want the destination folder to perfectly reflect the source folder, and that means deleting any files that have been deleted from the source folder.

I see some options listed in the manual page for rsync that might do the trick, but since I'm not familiar with.

Java 8 is now available according to http://openjdk.java.net/projects/jdk8/, but http://openjdk.java.net/install/ does not yet mention how to install OpenJDK 8 (not Oracle Java) on Ubuntu 14.04 Long Term Support. (For 14.10 and later just run apt-get install openjdk-8-jdk)

How and when can this be done?

(2017-08-08: The very short answer is: OpenJDK 8 as of 2017-08-08 is not officially available from the official repositories as an APT package for Ubuntu 14.04. See full summary in this answer - updated 2021-06-29)

Note: For now we will use Oracle Java - the optimal solution for me is, however, OpenJDK from the Ubuntu repositories, until Oracle Java is available directly and effortless from the Ubuntu repositories.

How do I check the SHA1 hash of a file?

I have used top to see the memory usage at the moment. But I would like to monitor the memory usage over a period of time. E.g start monitoring and then execute a few commands, and final stop the monitoring and see how much memory that have been used during the period.

How can I do this on Ubuntu Server?

I guess I could start a cronjob every 5th second or so, and invoke a command that log the current memory usage in a textfile. But what command should I use to get the current memory usage in a format that is easy to log to a text file?

If I want to make a backup of everything I have done since the fresh install of Ubuntu, what are the possible options? What all should I backup? I want to get all the settings that I changed, all the packages I installed, etc.