grub-install gives an error message I don’t understand
I'm new to Linux, am using CentOS 6.3, and am attempting to install CentOS 5.8 ISO to a pen-drive following instructions from here: http://ihazem.wordpress.com/2012/02/12/installing-centos-from-usb/
My pen-drive is /dev/sda and partion 1 is vfat. It's mounted on /mnt/usb. Here's what happens when I try to use grub-install:
[root@localhost ~]# grub-install –root-directory=/mnt/usb /dev/sda
This is the error message I get which I don't understand in this context:
"More than one install_devices? Usage: grub-install [OPTION] install_device Install GRUB on your drive.
-h, --help print this message and exit -v, --version print the version information and exit --root-directory=DIR install GRUB images under the directory DIR instead of the root directory --grub-shell=FILE use FILE as the grub shell --no-floppy do not probe any floppy drive --force-lba force GRUB to use LBA mode even for a buggy BIOS --recheck probe a device map even if it already exists This flag is unreliable and its use is strongly discouraged.
INSTALL_DEVICE can be a GRUB device name or a system device filename.
grub-install copies GRUB images into the DIR/boot directory specfied by --root-directory, and uses the grub shell to install grub into the boot sector."
What am I doing wrong?