The attached initrd is still containing the old code (and the old kernel, 3.19.0-18-generic). The new kernel is 3.19.0-21-generic, so the new initrd would be called initrd.img-3.19.0-21-generic.
The attached initrd is still containing the old code (and the old kernel, 3.19.0-18-generic). The new kernel is 3.19.0-21-generic, so the new initrd would be called initrd. img-3.19. 0-21-generic.