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Use df -h to see available space on mounted filesystems, and du to find how much space files and directories under a particular path use. The two commands answer different questions: one reports filesystem capacity; the other estimates usage within a directory tree.
Check available space with df
Run this for a human-readable overview of mounted filesystems:
df -hGNU df displays sizes using powers of 1024 with -h. Its output includes the filesystem, total size, used space, available space, percentage used and mount point. To check the filesystem that contains a particular location, give df a path:
df -h /varUse a directory such as / or /var rather than assuming a device name is the right target. Without an argument, df reports mounted filesystems; it does not inspect filesystems that are not mounted. GNU df uses powers of 1000 for its human-readable -H option instead of powers of 1024. See the GNU Coreutils documentation for df for option details. Other implementations and older versions may differ, so check the local manual if an option is unavailable.
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Find which directories use space with du
To get one total for a directory, use -s for a summary and -h for human-readable sizes:
du -sh /path/to/directoryTo see entries below that directory rather than a single total, run:
du -h /path/to/directoryWith GNU du, --max-depth=1 limits the report to the directory and its immediate children, which is often a useful first step when investigating a large tree:
du --max-depth=1 -h /path/to/directoryGNU du also supports --si for human-readable sizes using powers of 1000. Consult the GNU Coreutils documentation for du for the precise behavior of these options.
List large entries as a quick diagnostic
This pipeline prints numeric sizes and paths, sorts the entries from largest to smallest, and shows the first ten:
du -a /path/to/directory | sort -n -r | head -n 10It is a quick way to spot large entries, not a polished or universally portable report. Very large trees can take time to scan; permission errors may leave some paths uncounted, and filenames, locale settings or differences among command implementations can affect the output. Use it as a lead, then inspect the specific paths with du.
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Why df and du can disagree
df reports filesystem-level capacity and availability, while du estimates usage from file information reported by the operating system. Their results are not interchangeable measures of the same thing. Hard links, copy-on-write behavior, compression, network filesystems and filesystem metadata can all affect the relationship between a directory scan and device consumption. Access restrictions or differences in which paths are mounted can also keep a scan from accounting for everything shown by df.
If a filesystem looks full in df but a du scan does not explain the usage, treat the results as complementary clues: confirm you scanned the relevant mounted paths and consider filesystem behavior and access limits before concluding that space is missing.
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Background and compatibility
The Linux Foundation republished Jack Wallen’s Linux.com archive article on January 7, 2022, describing df as an overview of disk usage and du as a way to discover usage by directory. The commands are standard utilities commonly available on Linux systems, including headless setups; the article used Elementary OS as its example. The current GNU Coreutils documentation is version 9.11, but that does not mean every Linux distribution ships that release. For a broader introduction, the Linux Foundation article links to its free Introduction to Linux course.
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