this post was submitted on 25 Aug 2023
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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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How so?
On Windows, I often simply took out the USB drive without "safely removing" it. The data was there 99% of the time. On Linux, if I'm not mistaken, unmounting the drive before disconnecting is what actually writes data to it.
I don't think Linux literally waits for you to unmount the drive before it decides to write to it. It looks like that because the buffering is completely hidden from the user.
For example say you want to transfer a few GB from your SSD to a slow USB drive. Let's say:
In this scenario, the kernel will take half a minute to read the data into the RAM and then report that the file transfer is complete. Whatever program is being used will also report to the user that the transfer is complete. The kernel should have already started writing to the drive as soon as the data started being read into the RAM, so it should take another nine and a half minutes to complete the transfer in the background.
So if you unmount at that point, you will have to wait nine and a half minutes. But if you leave it running and try to unmount ten minutes later it should be close to instant. That's because the kernel kept on writing in the background and was not waiting for you to unmount the drive in order to commit the writes.
I'm not sure but I think on Windows the file manager is aware of the buffering so this doesn't happen, at least not for so long. But I think you can still end up with corrupted files if you don't safely remove it.
That can be configured with the
sync
option ofmount
.Or just
sync
before pulling it.Really? I've literally never done this but I suppose I really only use my USB for dd'ing a distro.