Unwanted permanent umount

The problem = I've got a simple question: what's the difference between ejecting flash drive using GNOME Files (formerly known as Nautilus ) button (see image below) and umount command? Before you will read rest of this question I encourage you to think if you expect any difference between results of clicking eject button in GNOME Files and typing umount command? If yes, then what's the difference? If no, then read on... --- 1st try: GNOME Files eject = When I insert my flash drive to my computer's USB socket, Debian automatically mounts it, which is reflected both in GNOME Files : and command line using e.g. df command: me@host:~$ df -h Filesystem Size Used Avail Use% Mounted on (...) /dev/sdf1 3,6G 3,6G 0 100% /media/me/Debian 9.1.0 amd64 1 or blkid command: root@host:~# blkid (...) /dev/sdf1: UUID="XXXX-XX-XX-XX-XX-XX-XX" LABEL="Debian 9.1.0 amd64 1" TYPE="iso9660" PTUUID="XXXXXXXX" PTTYPE="dos" PARTUUID="XXXXXXXX-XX" /dev/sdf2: SEC_TYPE="msdos" UUID="XXXX-XXXX" TYPE="vfat" PARTUUID="XXXXXXXX-XX" When I click eject button marked with a red circle: and I run those commands once again, there is no sdf string in commands' output (which is probably what I should expect after ejecting /dev/sdf1): root@host:~# df -h | grep sdf root@host:~# df -ah | grep sdf root@host:~# Note that I added -a (--all) flag to df command and I got the same (empty) result. root@host:~# blkid | grep sdf root@host:~# Note that now I'm unable to remount /dev/sdf1 without reinserting my flash drive: root@host:~# mkdir -p /mnt/test root@host:~# mount /dev/sdf1 /mnt/test mount: special device /dev/sdf1 does not exist --- 2nd try: umount command = Now repeat the hole procedure with only changing the way I unmount my flash drive. Instead of clicking eject button, I type: umount /dev/sdf1 Here is the result of df : root@host:~# df -h | grep sdf root@host:~# df -ah | grep sdf root@host:~# df result is probably as expected because it's the same as above... but here comes the blkid : root@host:~# blkid | grep sdf /dev/sdf1: UUID="XXXX-XX-XX-XX-XX-XX-XX" LABEL="Debian 9.1.0 amd64 1" TYPE="iso9660" PTUUID="XXXXXXXX" PTTYPE="dos" PARTUUID="XXXXXXXX-XX" /dev/sdf2: SEC_TYPE="msdos" UUID="XXXX-XXXX" TYPE="vfat" PARTUUID="XXXXXXXX-XX" Note that remounting works fine in opposite to the previous try: root@host:~# df -h | grep sdf root@host:~# mkdir -p /mnt/test root@host:~# ls /mnt/test | wc -l 0 root@host:~# mount /dev/sdf1 /mnt/test mount: /dev/sdf1 is write-protected, mounting read-only root@host:~# ls /mnt/test | wc -l 24 --- The question = Why is that? What is the precise, underlying reason of above differences in blkid output? Does GNOME Files do something more than umount command? It seems to me that GNOME File eject button is kind of 'permanent' unmount. Why?