用C++编程调用libvirt的API来创建KVM虚拟机

1. 如果已经写好了创建kvm的配置文件（stand.xml）格式，那么创建kvm虚拟机只要使用命令即可：

virsh define ./conf/stand.xml                                                                                                                                 
virsh start rheltest3

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2. 如果直接编程调用libvirt创建kvm虚拟机，则可用以下程序

/***************************************************************************
 * create_vm.cpp
 *  create kvm machine(domain) based on conf.xml
 *  the first parameter is the conf xml files' name
 *  Note: the .xml must has two boot types (cdrom/hd) by any order
 *  compile command: 'g++ create_vm.cpp -o createvm -lvirt'
 *  running command: './createvm  /path/to/xml/example.xml'
 *  author  : Aborn Jiang
 *  date    : Aug.17, 2013
 *  version : v0.1
 ***************************************************************************/

#include <iostream>
#include <cstdio>
#include <string>
#include <fstream>
#include <sstream>
#include <libvirt/libvirt.h>
#include <libvirt/virterror.h>
#include <memory.h>

using namespace std;
int main(int argc, char* argv[])
{
 if ( 1 == argc ) {
  cout << "must and only need an argument, this is, configure .xml file name." << endl;
  return -1;
 }
 if ( 3 <= argc ) {
  cout << "too many arguments. must and only need one, that is, .xml file name." << endl;
  return -1;
 }
 string xmlfile=argv[1];
 cout << "*************************" << endl;
 cout << "begin to build vm ..." << endl;
 cout << "xmlfile path:" << xmlfile <<endl;
 
 ifstream file(xmlfile.c_str());
 if (!file) {
  cout << "Cannot open file, permission denied." << xmlfile << endl;
  return -1;
 }
 stringstream buffer;
 buffer << file.rdbuf();
 string xmlcontents = buffer.str();
 file.close();
 
 /*************************************************************************************
  * deal with the original xml configuration file
  * initxmlconts for transient guest domain(install os) configure (boot from cdrom)
  * xmlcontents  for persistent guest domain configure (boot from hd)
  ************************************************************************************/
 int pos_boot  = xmlcontents.find("boot");
 int pos_hd    = xmlcontents.find("hd", pos_boot);
 int pos_cdrom = xmlcontents.find("cdrom", pos_boot);
 cout << "pos_hd=" << pos_hd << "  pos_cdrom=" << pos_cdrom << endl;
 string initxmlconts(xmlcontents);
 if ( pos_hd > pos_cdrom ) {    // cdrom apears in first order
  cout << "cdrom apears in first order" << endl;
  xmlcontents.replace(pos_cdrom, 5 ,"hd");
  pos_hd=xmlcontents.find("hd", pos_cdrom + 2);
  xmlcontents.replace(pos_hd, 2, "cdrom");
 } else {                    // hd apears in first order
  cout << "hd apears in first order" << endl;
  initxmlconts.replace(pos_hd, 2, "cdrom");
  pos_cdrom=initxmlconts.find("cdrom", pos_hd + 5);
  initxmlconts.replace(pos_cdrom, 5, "hd");
 }

 // create and boot a transient initial domain, for vm os installation
 virConnectPtr conn = virConnectOpen("qemu:///system");
 if (NULL == conn ) {
  virErrorPtr error = virGetLastError();
  cout << error->message << endl;
  return -1;
 }
 virDomainPtr vmpi = virDomainCreateXML(conn, initxmlconts.c_str(), VIR_DOMAIN_START_AUTODESTROY);
 if (NULL == vmpi) {
  virErrorPtr error = virGetLastError();
  cout << error->message << endl;
  return -1;
 }
 cout << "os installation ongoing, it will spend some time..." << endl;
 while ( 1 == virDomainIsActive(vmpi) );                // waiting until installation finish.
 cout << "os installation finished..." << endl;
 if (NULL == conn)
  virConnectPtr conn = virConnectOpen("qemu:///system");
 cout << "start boot the vm machine..." << endl;

 // store xmlcontents configuration for a persistent guest domain and boot it.
 virDomainPtr vmp = virDomainDefineXML(conn, xmlcontents.c_str());
 if (NULL == vmp) {
  virErrorPtr error = virGetLastError();
  cout << error->message << endl;
  return -1;
 } else {
  cout << "define persistent domain success." << endl;
  if (virDomainCreate(vmp) < 0) {                  // boot the vm.
   cout << "Unable to boot guest configuration." << endl;
  } else {
   cout << "Boot the persistent defined guest ..." << endl;
  }
  cout << "build vm finished." << endl;
  cout << "*************************" << endl;
  return 0;
 }
}