#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>

_PROTOTYPE(void error, (char *message)	);

int main(int narg,char *argv[])
{  unsigned size;
   char mbr[512];
   int fd;

   if(narg!=3) error("Usage: vdisk size");
   size=atoi(argv[1]);   
   if((fd=open(argv[2],O_RDONLY))<0) 
		error("Error ocurred during an I/O operation");
   read(fd,mbr,sizeof(mbr));
   close(fd);
   if((fd=open("hd0",O_RDWR | O_CREAT))<0) 
		error("Error ocurred during an I/O operation" );
   write(fd,mbr,sizeof(mbr));
   lseek(fd,size*512-4,SEEK_SET);
   write(fd,&size,sizeof(size));
   close(fd);
}

void error(char *message)
{
  fprintf(stderr,"%s\n",message);
  exit(1);
}