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TFA mentions that you can use sync after cp to do the same thing as fdatasync. You can't "unmount the file system" because you're writing directly to the block device, the thumb drive isn't mounted.

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Syncing as you go (ideally asynchronously) when you have to sync anyway (like when you're writing an image to a thumb drive, or write to NFS) has the big advantage that you don't end up saying "I'm done writing all data" and then blocking for five minutes waiting for the kernel to flush a couple gigs to disk.

For removable media, I believe that finishing up with "eject" would be the safest way to ensure that all writes were committed to the hardware.

You can't "unmount the file system" because you're writing directly to the block device, the thumb drive isn't mounted.

("Eject" is macOS's term for "unmount filesystem")

Distrowatch.com is a site promoting use of Linux and BSD.

"eject" is a Linux command which attempts to safely disconnect removable media.

https://manpages.ubuntu.com/manpages/noble/en/man1/eject.1.h...

TFA doesn't mention filesystems at all, sort of jumps in where we find the block device. Things could become messy if the device were mounted while the copy is attempted.

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