ipxe boot thinstation ?

[zulinfi]

when use script
kernel ${base-url}/boot/vmlinuz
initrd ${base-url}/boot/initrd
imgargs vmlinuz splash=silent,theme:default load_ramdisk=1 ramdisk_blocksize=4096 root=/dev/ram0 ramdisk_size=786432 console=tty1 vt.global_cursor_default=0 quiet loglevel=3 LM=3
boot || goto failed

Get error

kernel panic - not syncing :VFS: Unable to mount root fs on unknown-block(1,0)
kernel Offset: disabled
---[ end Kernel panic - not syncing: VFS: Unable to mout root fs on unknown-block(1,0)

what's wrong?