I have a problem with hidden disk usage on my Ubuntu 22.04. As you can see, the ncdu utility only finds ~30GB on the system:
Whereas Ubuntu's System Monitor finds that 88 GB are being used:
What's going on here?
Output of df -h:
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KSHMR
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I also wonder where this "Apparent size: 128 Tb" comes from. – Jos May 26 '23 at 16:10
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The red ! at the start of many of the entries means there is an error while reading the directory. I guess that might be an ownership issue so try it with sudo. Did you use the -x option? That stops the scan crossing filesystem boundaries. Without the -x I too get the crazy high 128TB. With the -x option I get a realistic number. So try `sudo ncdu -x /` – PonJar May 26 '23 at 20:16
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Files can be invisible (but using disk space) for several reasons. Programs can create temporary files, `open`, `unlink`, and use them very privately, with guaranteed deletion no matter how the program `exit`s. Files can get really big, if some budding sysadmin deleting a log file that some process has open (and is about to write block N+1) without notice. You can investigate open files with `sudo lsof`, followed by lots of options. Read `man lsof sudo`. – waltinator May 27 '23 at 01:13
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https://askubuntu.com/questions/5980/how-do-i-free-up-disk-space – Hannu May 27 '23 at 07:08