两种解决办法：
方法A:
mkdir /cdrom
mount -t vfat /dev/sda1 /cdrom
modprobe loop
losetup /dev/loop6 /cdrom/boot/iso/archlinux-2011.08.19-core-i686.iso
ln -s /dev/loop6 /dev/disk/by-label/ARCH_201108
exit
``
方法B:add earlymodules=loop as bootparam
grub设置菜单项：menuentry "ArchLinux-2011.08.19-core-i686.iso" {
set isofile="/boot/iso/archlinux-2011.08.19-core-i686.iso"
set dev_label="MULTIBOOT"
loopback loop $isofile
linux (loop)/arch/boot/i686/vmlinuz archisolabel=ARCH_201108 img_dev=/dev/disk/by-label/$dev_label img_loop=$isofile earlymodules=loop
initrd (loop)/arch/boot/i686/archiso.img
}
```