Hello All

I copied one .iso file of size 5 GiB to Pen drive, and after the process completed, I entered the 'sync' command. It took several more minutes to finish the sync.

If I hadn't known about the sync command and had I pulled the USB pen drive, I would have lost the data.

So, is there a way to copy a file to USB or anywhere without using a cache buffer?

Thanks

Just doing a standard "Eject USB" does the same thing, so even if you didn't know about sync you would have been fine, providing you didn't just yank the drive out. And no, there isn't.

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Sorry, I forgot to mention the copy process was in the terminal with the 'cp' command. No GUI, and was hoping for a solution in the terminal.

The command to safely remove media is umount - it will (afaik) perform equivalent action to sync.

Note that it's umount - not unmount. Some distros do provide an unmount command, but it's not standard.

I don't know of a specific "copy then safely remove" option, but no doubt someone somewhere has created a wrapper to do that.

Again, if you just yank the drive out it'll lose data. Again, there is no way to 'write' without that buffer...I'll leave it to you to consider why, and point out the difference in speeds between USB, SSD's/HDD's, etc.

As boughtonp said, umount does the sync for you...same as if you click "Eject Media" (or whatever it is on your GUI).

Many, if not all, GUI file managers also include a right-click menu item to "safely remove" a removable device. If it's not safe to remove yet, the file manager normally will not allow removal.

Simple answer -- No!
All writes to any device are cached and the cache is cleared when the write is complete. Reading is faster than writing so the system always uses a cache during write operations. It takes time to write large quantities of data to a flash drive and it must be complete before the drive is pulled or data corruption will occur.

Using the command "sync" will force the write to complete and the cache to clear but you have to wait for the command prompt to return which indicates the cache is clear.
The "eject" command works similarly but again you must wait for the command prompt to return.

@frankbell gives the info about the gui method. I will note that the later versions of the nautilus file manager put a progress "pie" in the upper right of the window label bar near the minimize, maximize, and close buttons that fills with color as the write proceeds and disappears when done. I believe closing the file manager which started the write/copy before it completes may also interrupt the write but have not tested that myself.

For that reason, I have started to use rsync with --progress. Yes, to copy files to and from USB / pen drive to local drive.

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