用C++編程調用libvirt的API來創建KVM虛擬機

1. 如果已經寫好了創建kvm的配置文件（stand.xml）格式，那麼創建kvm虛擬機只要使用命令即可：

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

相關閱讀：

使用 libvirt創建和管理KVM虛擬機 http://www.linuxidc.com/Linux/2012-06/62934.htm

應用Libvirt連接KVM虛擬化平台 http://www.linuxidc.com/Linux/2013-02/79939.htm

Ubuntu下用libvirt安裝KVM虛擬機時找不到/bin/qemu-kvm問題解決 http://www.linuxidc.com/Linux/2013-08/88985.htm

2. 如果直接編程調用libvirt創建kvm虛擬機，則可用以下程序

/***************************************************************************
* 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;
}
}