CachyOS Apps

F3 on CachyOS: install, first run, settings and fixes

Simple tool that tests flash cards capacity and performance to see if they live up to claimed specifications.

From the official CachyOS repo. Install with pacman, no AUR helper needed.

Written from the sources listed at the end · Nov 2, 2026 · F3 app page, reviews and trust score

Install F3 with pacman

  1. Install f3 from the official cachyos repo. pacman checks the package signature before it installs.
    sudo pacman -S f3

First run

  1. Find the device you want to test. lsblk shows an overview of your current devices; the examples below use /dev/sdX as a placeholder.
    lsblk
  2. Test performance: f3write writes large files to the mounted drive, then f3read checks that the drive returns exactly what was written. Run them in this order and replace the path with your drive's mount point.
    f3write /run/media/$USER/DRIVE/
  3. Then read the files back.
    f3read /run/media/$USER/DRIVE/

Key settings

  1. For a quick capacity test, f3probe works directly on the unmounted block device and needs root. It is the fastest test and only writes what it needs. It destroys any data on the drive.
    sudo f3probe --destructive --time-ops /dev/sdX
  2. f3fix creates a partition that fits the real size of a fake drive. Take the last sector from the f3probe output.
    sudo f3fix --last-sec=16477878 /dev/sdX

Common fixes

Which f3 tool should I use?

f3write and f3read test a mounted drive and keep it usable. f3probe is faster and suits large drives, but it works on the raw device and erases it.

Sporadic corruption on a drive that is not fake

The README calls this flaky flash. On a FAT formatted drive, Flakyflash can find the bad clusters and mark them, but the drive should still be treated as failing and replaced.

Uninstall F3

  1. Remove f3 and the dependencies nothing else needs.
    sudo pacman -Rns f3

Sources