But when I trye: # [root@test boot]# mkinitrd -v initrd-2.6.18-194.11.1.el5xen.img 2.6.18-194.11.1.el5xen   prints as belows:
Creating initramfs
Looking for deps of module ehci-hcd
Looking for deps of module ohci-hcd
Looking for deps of module uhci-hcd
Looking for deps of module ext3: jbd 
Looking for deps of module jbd
Looking for driver for device sda2
Looking for deps of module pci:v00001000d00000060sv00001028sd00001F0Cbc01sc04i00: scsi_mod megaraid_sas 
Looking for deps of module scsi_mod
Looking for deps of module sd_mod: scsi_mod 
Looking for deps of module megaraid_sas: scsi_mod 
Looking for deps of module pci:v000010B5d00008518sv00000000sd00000000bc06sc04i00: shpchp 
Looking for deps of module shpchp
Looking for deps of module pci:v000010B5d00008518sv00000000sd00000000bc06sc04i00: shpchp 
Looking for deps of module pci:v00001166d00000144sv00000000sd00000000bc06sc04i00: shpchp 
Looking for deps of module sata_svw: scsi_mod libata 
Looking for deps of module libata: scsi_mod 
Looking for deps of module xen-vbd
No module xen-vbd found for kernel 2.6.18-194.11.1.el5xen, aborting.
That's why?