14. Disk usage

No disk can hold an infinite amount of data. These commands report how much disk storage is in use or available, report other file and file status information, and write buffers to disk.

14.1 `df`: Report file system disk space usage		Report file system disk space usage.
14.2 `du`: Estimate file space usage		Estimate file space usage.
14.3 `stat`: Report file or file system status		Report file or file system status.
14.4 `sync`: Synchronize data on disk with memory		Synchronize memory and disk.