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Run df -h to see which mounted filesystem is short on space, then use du or ncdu to locate large directories on that filesystem. Identify what the files are before removing anything, and finish by checking df -h again.
1. Find the filesystem that is running low
Open a terminal and run:
df -hThe command reports capacity and available space for mounted filesystems in human-readable units. Its results answer which filesystem is full; they do not identify the files using the space. To check the filesystem containing a particular location, pass that path:
df -h /homedf reports mounted filesystems, not the capacity of an unmounted disk or partition. See the GNU Coreutils documentation for df.
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Use the mount point or directory associated with the full filesystem. On GNU/Linux systems with the relevant GNU du options, run:
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du -xhd1 /pathReplace /path with the directory you want to inspect—for example, /home if that is where your space issue is. The options limit the summary to one directory level (-d1) and keep the scan on the same filesystem (-x). If a directory stands out, run the command again using that directory as the path to inspect its contents in more detail.
du recursively estimates the space used by the files and directories it can scan. Permission restrictions can hide some content, and crossing into another filesystem can make a scan irrelevant to the capacity reported for the filesystem you are investigating. For option details, see the GNU Coreutils documentation for disk usage.
3. Browse interactively or use an Ubuntu desktop tool
Terminal browser: ncdu
If you prefer navigating a directory tree interactively, use:
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ncdu -x /pathThis provides a terminal-based view of directory usage while keeping the scan on one filesystem. The Ubuntu Noble manual for ncdu documents version 1.19-0.1 and a read-only mode, -r, which disables deletion and shell-spawning features. The available version and options can differ across distributions.
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Ubuntu’s desktop documentation lists Disk Usage Analyzer, System Monitor, and Usage for checking capacity and folder usage. The applications and labels available depend on the desktop release; consult the Ubuntu Disks & storage guide.
4. Decide what is safe to remove
Inspect the large directories rather than deleting a file or system folder just because it is big. Common places to review include Downloads, media collections, virtual-machine images, containers, and project or build files. Ubuntu recommends understanding what is taking space before choosing what to remove, and leaving system-side content alone unless you understand the operation.
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- For personal files you want to remove from the internal disk, make a separate backup first. Ubuntu recommends keeping important personal files in a separate location, preferably on another device such as an external disk. Confirm the copy is complete before deleting the originals.
- For caches, logs, or application data, identify the relevant tool and what its cleanup operation removes. Avoid manually deleting unfamiliar system files.
Ubuntu’s advice is to determine “what takes your space and what you can do to potentially remove some of the unwanted stuff.” Read its disk-usage guidance before making changes you do not understand.
5. Use cleanup commands only when they apply
APT cache and unused dependencies on Debian or Ubuntu
These commands are for APT-based systems, not every Linux distribution:
sudo apt cleanclears retrieved package files from APT’s cache.sudo apt autocleanremoves cached package files that can no longer be downloaded.sudo apt autoremoveremoves packages installed automatically as dependencies that are no longer needed. Review the proposed removal list before confirming.
These operations do different things; choose based on what you intend to remove. The Ubuntu Noble APT manual documents package-handling behavior.
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Archived systemd journal files
If your system uses the systemd journal, first inspect its disk usage:
journalctl --disk-usageYou can then set an example size or time bound for archived journal files:
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6. Verify the space you recovered
Run df -h again and check the filesystem you were investigating. If its usage still does not seem to match the directories you inspected, check these possibilities:
- The scan crossed filesystems: use
-xwith GNUduorncduto keep the scan on one filesystem. - Permissions hid files: an unprivileged scan may not be able to read every directory.
- Sparse files affect the comparison: apparent file size can differ from allocated disk usage, so
dutotals need not match filesystem totals exactly.
Remember the distinction: df reports filesystem capacity and availability, while du and ncdu estimate usage within directory trees. Their figures answer different questions and may not match exactly.
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