On Wed, Feb 08, 2023 at 04:50:32PM +0100, Jan Stary wrote:
| On Feb 08 13:56:18, pe...@bsdly.net wrote:
| > 1) close any open files stored there
| > 2) make sure no process has the media as $PWD (as in, cd away from there,
| > and really a variation on the first)
| > 3) issue at least one sync command (some folklore will insist on three)
| > 4) umount the media from wherever it was mounted
|
| 4 takes care of 1,2,3, right?
Not if the kernel has a file open on it (e.g. a swap file [1]) or if
there's another mount somewhere in the filesystem you're trying to
unmount (a special case of the first condition, I guess).
[weerd@kale] $ doas mount /dev/sd3a /mnt
[weerd@kale] $ doas mkdir /mnt/deeper
[weerd@kale] $ doas mount /dev/sd3d /mnt/deeper
[weerd@kale] $ doas dd if=/dev/zero of=/mnt/swap bs=1M count=4096
[weerd@kale] $ doas swapon /mnt/swap
The kernel is not going to let you `umount /mnt`, and forcibly
removing the device is very likely going to lead to amazing new
learning opportunities.
So, yeah, as people have stated .. the way to safely remove a USB
drive from your system depends on what you were using the USB drive
for. For the generic case, where we have no clue what OP was doing:
shut down your machine first and remove the device then.
Paul
[1]: Putting swap on removable media is a tremendously bad idea -
don't do it, unless you're keen on those learning opportunities.
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