Differences in "ejecting" and "safely removing" are explained under this question
but I can not find an explanation for why some pen drives are not presented with an option to safely remove, and can only be ejected. Drives also get different icons in launcher - some look like a usb stick, some look like a hdd with usb logo on top and it seems that only those with the "disk" icon can be safely removed. What causes these drives to appear and / or behave different from each other?
Screenshot from 14.04, icon on top belongs to Bus 001 Device 006 and lower icon belongs to Bus 002 Device 003:
lsusb
Bus 002 Device 003: ID 0930:6545 Toshiba Corp. Kingston DataTraveler 102/2.0 / HEMA Flash Drive 2 GB / PNY Attache 4GB Stick
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 002: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 006: ID 090c:1000 Silicon Motion, Inc. - Taiwan (formerly Feiya Technology Corp.) Flash Drive
In my 16.04 machine the Bus 001 Device 006 usb drive shows up as an "usb disk" icon, instead of the memory card (?) icon like here. Only the icon is different, otherwise the behavior is the same.
/dev/sdxwithsudo umount /dev/sdx*you can unplug it safely. You can also remount a partition withmount /dev/sdxn /mountpointbut if you 'eject' a USB pendrive it will not only be unmounted, but the current will also be switched off, and you must unplug and replug it to be able to mount it again. In general, there is a difference between internal drives, that are usually not switched off, only unmounted, and some USB drives are made to appear as internal drives (seen as ATA drives rather than USB drives). – sudodus Apr 12 '17 at 17:51