I don't really care what filesystem my devices are, as long as I can read and write them. So FAT32 would be a decent choice, right? No. FAT32 has a file size limit of only 4G and I tend to store larger stuff on my Corsair Flash Survivor. I came up with two different solutions:
1. Create two separate partitions, one with stuff GRUB needs access to, one with large stuff like the filesystem images and my data,
2. Create a NTFS partition and boot from that.
Of course I first came up with solution 2, but I couldn't find much information about grub and ntfs, except for total lack of support for ntfs. I was thinking about solution 1 and then decided it sucks if you're forced to use two partitions while you don't really want to, so I went on looking for booting from ntfs drives.
After a while I came upon grub4dos. I can't say I really love it (without spending any time investigating it seems it's more of a hack than an enhancement to grub), but it's grub and it boots from ntfs formatted drives. Once I had that figured out, it was time to start doing some work.
First, partition the flash drive so there's a large ntfs partition (in my case the whole 16G). In my case there was already a partition there, if there's not you can skip deletion of the partition.
# fdisk /dev/sdx
Command (m for help): d
Selected partition 1
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-125, default 1): [return]
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-125, default 125): [return]
Using default value 125
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 7
Changed system type of partition 1 to 7 (HPFS/NTFS)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
Now it's time to create a filesystem on the flash drive, since we've chosen ntfs we'll need ntfsprogs, your linux distribution probably has it in it's repositories. Enter the following command to format the drive:
# mkfs.ntfs -L label -Q /dev/sdxY
Cluster size has been automatically set to 4096 bytes.
Creating NTFS volume structures.
mkntfs completed successfully. Have a nice day.
This shouldn't have been hard, if I actually needed to explain those steps to you at all, so let's continue with the serious part. The next few steps need a grub4dos archive. You can find one at their downloads page, I took grub4dos-0.4.4-2009-03-07.zip. Extract this and open a command line in the directory where the extracted files are. Now enter the following command:
# ./bootlace.com /dev/sdx
Disk geometry calculated according to the partition table:
Sectors per track = 63, Number of heads = 255
Success.
If it says Success or something similar, then grub4dos is on your flash drive. You can actually boot from it, however for grub4dos to be useful it needs some files. Copy grldr to your flash drive (of course you need to mount it for that). It should be in the root of the drive. Now create a menu.lst in the root of the drive too (yes, this differs from grub behaviour). Edit the menu.lst file so it resembles a usable grub menu.lst and you're done.
The following block is my menu.lst, if there's any interest in the files and layout I used then just leave a comment and I'll be sure to answer any questions about it.
default 0
timeout 60
splashimage=/boot/splash.xpm.gz
title Ubuntu Jaunty Alternate Install AMD64
kernel /ubuntu/jaunty/vmlinuz
initrd /ubuntu/jaunty/initrd.gz
title Gentoo Minimal X86
kernel /gentoo/x86/gentoo root=/dev/ram0 init=/linuxrc looptype=squashfs loop=/gentoo/x86/image.squashfs cdroot
initrd /gentoo/x86/gentoo.igz
title Gentoo Minimal AMD64
kernel /gentoo/amd64/gentoo root=/dev/ram0 init=/linuxrc looptype=squashfs loop=/gentoo/amd64/image.squashfs cdroot
initrd /gentoo/amd64/gentoo.igz
title GParted
kernel /gparted/vmlinuz boot=live union=aufs noswap vga=791 ip=frommedia nolocales live-media-path=gparted
initrd /gparted/initrd1.img
title Memtest 86+
kernel /memtest86/memtest86-3.5
title Boot first harddisk
rootnoverify (hd1)
chainloader +1
title Reboot
reboot
title Shut down
halt