Check used disk space on Linux with du: 
No matter how much storage space you have, there’s always the possibility for it to fill up. On most personal devices, drives get filled up with photos and videos and music, but on servers, it’s not unusual for space to diminish due to data in user accounts and log files. Whether you’re in charge of managing a multi-user system or just your own laptop, you can check in on disk usage with the du command.
By default, du provides the amount of disk space used in your current directory, as well as the size of each subdirectory:
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