I want to put a bunch of minor emergency operating systems (such as GParted Live, DSL, Puppy Linux and so on) on a partitioned USB pen drive, with a dedicated grub boot loader on it, which I want to start when I select the drive in the BIOS to boot. The problem is: when writing grub boot options I must tell where kernel and initial ram files are located, but the USB drive can have different letters depending on when I did plug it in, if some others external drive were mounted. So, how can I write appropriate options which automatically refer to the drive grub is installed on without having to specify absolute paths, which might change (I mean, like (hd1,msdos1) ot /dev/sdb1)?

And, while we are at it, can I have grub working on a device without an operating system on it to which it can refer? I mean, I want to address the command sudo grub-install /dev/sdb from the LMDE system I'm on right now, but I won't have LMDE on my pen drive. Is that a problem? And installing grub on another device, will I keep the grub I have right now on my HDD?