What makes a mount point removable in Linux? I am using Gentoo Linux with Gnome 3.2, and I find it annoying that some of my drives (ex: /dev/sdb) appear as removable but not the others (ex: /dev/sdc, /dev/sdd).

They are all in /etc/fstab, with the same options. They are all mounted properly at startup, they all work fine under my own folders /mnt/drive2 /mnt/drive3 /mnt/drive4. But only one of them (the first) appears in Nautilus (and in the Gnome 3 notification tray) as mountable/removable, not the others. Can I add options to my fstab to hide it? Or can I probe using udevadm or whatever? It looks strange to be able to remove/unmount fixed drives that I never need to unmount nor remove.

Any pointer would be good, thanks.