Why is my partition claiming to be out of space?

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http://askubuntu.com – My file system claims to only have 4.5 GB left. While my OS (a folder with in file system) still has 75.2 GB left. I put something near 130 GB on my Ubuntu partition, it should have enough space. I confirmed that I can put things in OS that exceed the space in available file systems, but that makes no sense, OS is listed as a folder inside of file system, why would it have more space than it's parent folder? What is going on? Here is the output of df: Filesystem 1K-blocks Used Available Use% Mounted on /dev/sda5 113773200 103741440 4252408 97% / udev 2004600 4 2004596 1% /dev tmpfs 804756 84 (HowTos)