一、简介

qemu-ga是在虚拟机中安装的一个agent，宿主机host通过通道（unix socket）与虚拟机vm内部的agent进行通信，这样宿主机就有了一种从外部控制/获取虚拟机的手段。比如：host可以向vm下发执行修改hostname的指令，或者获取vm内所有进程信息的指令。

qemu-ga时刻监听这个unix socket，一旦发现有指令发送来，分析该指令，并执行，通过unix socket返回执行结果，传输的是json字符串。

二、详解

1、centos6下使用qemu-ga

（1）虚拟机连接本机及网络，然后在虚拟机中安装qemu-ga（windows是qemu-ga.exe）

yum install qemu-guest-agent

（2）修改安装后的qemu-ga配置文件

#修改/etc/sysconfig/qemu-ga文件将 # Enable fsfreeze hook. See the --fsfreeze-hook option in "qemu-ga --help".FSFREEZE_HOOK_ENABLE=0改为# Enable fsfreeze hook. See the --fsfreeze-hook option in "qemu-ga --help".FSFREEZE_HOOK_ENABLE=1

#修改/etc/sysconfig/qemu-ga，注释掉BLACKLIST_RPC这一行，将所有功能开放将BLACKLIST_RPC="guest-file-open,guest-file-close,guest-file-read,guest-file-write,guest-file-seek,guest-file-flush"改为#BLACKLIST_RPC="guest-file-open,guest-file-close,guest-file-read,guest-file-write,guest-file-seek,guest-file-flush"

（3）将虚拟机关机，在虚拟机配置文件libvirt.xml中的<devices>下面添加下述配置，并重新启动虚拟机

（4）测试是否正常

#得到虚拟机对应的domain id[root@node-12 ~]# virsh list Id    名称                         状态---------------------------------------------------- 90    instance-0000209f              running #使用命令进行测试[root@node-12 ~]# virsh qemu-agent-command 90 '{"execute":"guest-info"}'{"return":{"version":"0.12.1","supported_commands":[{"enabled":true,"name":"guest-set-vcpus"},{"enabled":true}...

（5）freeze文件系统的方法

#直接用virsh命令，freeze文件系统[root@node-12 ~]# virsh qemu-agent-command 90 '{"execute":"guest-fsfreeze-freeze"}'{"return":1} #freeze后，可以查询当前虚拟机文件系统的状态，表明是frozen[root@node-12 ~]# virsh qemu-agent-command 90 '{"execute":"guest-fsfreeze-status"}'{"return":"frozen"} #thaw（解封）文件系统[root@node-12 ~]# virsh qemu-agent-command 90 '{"execute":"guest-fsfreeze-thaw"}'{"return":1} #thaw后，文件系统为解封状态[root@node-12 ~]# virsh qemu-agent-command 90 '{"execute":"guest-fsfreeze-status"}'{"return":"thawed"}

2、python使用qemu-ga（类实现）

from commands import getstatusoutputimport loggerimport os, sys, statimport json  import base64  import crypt  import stringimport random  import reimport socket########################Configure############################FILE_OPEN_READ="""{"execute":"guest-file-open", "arguments":{"path":"%s","mode":"r"}}"""  FILE_OPEN_WRITE="""{"execute":"guest-file-open", "arguments":{"path":"%s","mode":"%s"}}"""  FILE_READ="""{"execute":"guest-file-read", "arguments":{"handle":%s,"count":%d}}"""FILE_WRITE="""{"execute":"guest-file-write", "arguments":{"handle":%s,"buf-b64":"%s"}}"""   FILE_CLOSE="""{"execute":"guest-file-close", "arguments":{"handle":%s}}""" class QemuQuestAgent:    def __init__(self):        self.__socketFileName = ""        self.__totalSize = 0        self.__currentSize = 0    def setSocketFile(self, filename):        self.socketFileName = filename        if not os.path.exists(self.socketFileName):            logger.error("%s do not exist!", self.socketFileName)            return False        return True            def resetPassWord(self, newPassword):        passwordFile = "/etc/shadow"        content = self._QemuQuestAgent__guestFileRead(passwordFile)        if not content.strip():            return False         content = base64.standard_b64decode(content)        user_array = re.split("\n",content)          for iter,line in enumerate(user_array):              info = line.split(":")              if info[0] == "root":                  info[1] = self._QemuQuestAgent__generationPwd(newPassword)                  user_array[iter] = ":".join(info)                  break        content = base64.standard_b64encode("\n".join(user_array))        write_count = self._QemuQuestAgent__guestFileWrite(passwordFile, content, "w+")        if write_count > 0:            logger.info("change password successfully!")            return True        else:            return False              def putFileToVM(self, fileName, vmFilePathName):        if not os.path.exists(fileName):            logger.error("%s do not exist" % (fileName))            return False        if vmFilePathName[-1] == "/":            vmFilePathName += fileName.split("/")[-1]        filestats = os.stat(fileName)        self.__totalSize = filestats[stat.ST_SIZE]        if self.__totalSize <= 0:            logger.error("%s is Empty!" % (fileName))            return False        fd = open(fileName, "r")        self.__currentSize = 0        total = 0        while True:            content = fd.read(4096)            total += 4096;            self.__currentSize += len(content)   #<=4096            content = base64.standard_b64encode(content)                  write_count = self._QemuQuestAgent__guestFileWrite(vmFilePathName, content, "a+")            if write_count <= 0:                fd.close()                return False            if total >= self.__totalSize:                break        fd.close()        return True        def processWrite(self):        return (self.__currentSize, self.__totalSize)            def __getResult(self, command, fileName = ""):        resultStr = ""        if fileName.strip():            self.socketFileName = fileName        if not os.path.exists(self.socketFileName):            return None;               sockfd = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)        server_address = self.socketFileName        try:            sockfd.connect(server_address)        except socket.error, msg:            logger.error("guestagent:%s,%s", socket.error, msg)            return None        try:            sockfd.send(command)            resultStr = sockfd.recv(10240)        finally:            sockfd.close()        return None if not resultStr else json.loads(resultStr);                def __generationPwd(self, pwd):        salt=''.join(random.choice(string.ascii_letters + string.digits + "./") for _ in range(16))          return crypt.crypt(pwd, "$6$%s" % salt)        def __guestFileRead(self, path):        file_handle = -1        content = self._QemuQuestAgent__getResult(FILE_OPEN_READ % (path))        if not content:           return ""        file_handle = content["return"]        if file_handle == -1:            return ""        file_content = self._QemuQuestAgent__getResult(FILE_READ % (file_handle,102400))["return"]["buf-b64"]        self._QemuQuestAgent__getResult(FILE_CLOSE % file_handle)         if not file_content:            return ""        else:            return file_content    def __guestFileWrite(self, path, content, mode):          file_handle = -1          content = self._QemuQuestAgent__getResult(FILE_OPEN_WRITE % (path, mode))        if not content:           return -1        file_handle = content["return"]        if file_handle == -1:            return -2        write_count = self._QemuQuestAgent__getResult(FILE_WRITE % (file_handle,content))["return"]["count"]        self._QemuQuestAgent__getResult(FILE_CLOSE % file_handle)          return write_count ########################test############################def testagent():    instance = QemuQuestAgent()    if instance.setSocketFile("/var/lib/libvirt/qemu/test.agent"):        if instance.resetPassWord("abc123"):            return True        if instance.putFileToVM("test.py", "/root/test.py"):            return True    return Falseif __name__ == '__main__':      testagent()

3、Qt使用qemu-ga

（1）qemuquestagent.h

#ifndef QEMUQUESTAGENT_H#define QEMUQUESTAGENT_H#include 
   
    #include 
    
     #include 
     
      #include 
      
       /*********************** *
       
         *  
         *  
         *
        * * qemu-ga --daemonize -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0 * **********************//*************QemuQuestAgent*****************/class HostConnectVM;class ResetPassWord;class FileManager;class QemuQuestAgent{public:    QemuQuestAgent();    ~QemuQuestAgent();    void getQGACommandAll();    void resetPassWord();    void fileOperation();private:    HostConnectVM *hostVM;    ResetPassWord *passWord;    FileManager *fileManager;    QString socketFileName;};/*************ResetPassWord*****************/class ResetPassWord{public:    ResetPassWord(HostConnectVM *host);    ~ResetPassWord();    int checkOldPassWord(const QString &password);    int setNewPassWord(const QString &password);private:    QString passwdFileRead();    bool passwdFileWrite(const QString &password);    bool openFile(QString mode);    void closeFile();    QString generationNewPassWord(const QString &password);private:    int fileHandle;    QString filePasswd;    HostConnectVM *pwHost;    QStringList lineContent;};/*************FileManager*****************/class FileManager{public:    FileManager(HostConnectVM *host);    ~FileManager();    int getFile(const QString &filePathName, const QString &localPath = "");    int putFile(const QString &localPathName, const QString &clientPathName);    bool getFileContent(const QString &filename, const QString &localPathName);    bool putFileContent(const QString &localName, const QString &clientName);private:    int openFile(const QString &filename, const QString &mode);private:    HostConnectVM *fmHost;};#endif // QEMUQUESTAGENT_H

（2）qemuquestagent.cpp

#include 
   
    #include 
    
     #include "qemuquestagent.h"#include "questagentcomponent.h"#include "defineconstants.h"#include "jsonparse.h"#include "base64.h"/*************QemuQuestAgent*****************/QemuQuestAgent::QemuQuestAgent(){    socketFileName = "/var/lib/libvirt/qemu/test.agent";    hostVM = new HostConnectVM(socketFileName);    passWord = new ResetPassWord(hostVM);    fileManager = new FileManager(hostVM);}QemuQuestAgent::~QemuQuestAgent(){    if (hostVM) {        delete hostVM;        hostVM = NULL;    }    if (passWord) {        delete passWord;        passWord = NULL;    }    if (fileManager) {        delete fileManager;        fileManager = NULL;    }}void QemuQuestAgent::getQGACommandAll(){    QString info = hostVM->getResult(GUEST_INFO);    qDebug() << __FUNCTION__<<__LINE__ << info;    if (info == "error2") {        qDebug() << "can not conncet to the client of VM";    }}void QemuQuestAgent::resetPassWord(){    QString oldPassWord = "abc123";    QString newPassWord = "abc124";    int flag = passWord->checkOldPassWord(oldPassWord);    if (flag == 1) {        qDebug() << "old password is wrong";    }    else if (flag == 0){        qDebug() << "password is right";        if (passWord->setNewPassWord(newPassWord) == 0) {            qDebug() << "set newpassword succeed";        }        else {            qDebug() << "set newpassword failed";        }    }    else {        //qDebug() << __LINE__ << "the client of VM is off";    }}void QemuQuestAgent::fileOperation(){    qDebug() << "---fileOperation---";    QString file = "/tmp/test1K.iso";    fileManager->getFile(file, "/tmp/abc/");    //fileManager->putFile("/tmp/abc/test1M.iso", "/tmp/");}/*************ResetPassWord*****************/ResetPassWord::ResetPassWord(HostConnectVM *host)    : fileHandle(-1){    filePasswd = "/etc/shadow";    pwHost = host;}ResetPassWord::~ResetPassWord(){}int ResetPassWord::checkOldPassWord(const QString &password){    if (openFile("r") == false) {        return -1;    }    QString fileContent = passwdFileRead();    closeFile();    lineContent.clear();    lineContent = fileContent.split("\n");    for (int index = 0; index < lineContent.size(); ++index) {        QStringList fields = lineContent.at(index).split(":");        if (fields.at(0) == "root") {            QStringList passwdList = fields.at(1).trimmed().split("$");            QString saltBuff = QString("$%1$%2").arg(passwdList[1]).arg(passwdList[2]);            char *shadowPwd = crypt(password.toStdString().data(), saltBuff.toStdString().data());            if (!strcmp(shadowPwd, fields.at(1).trimmed().toStdString().data())) {   //compare old and new password                return 0;            }            else {                return 1;            }        }    }    return false;}int ResetPassWord::setNewPassWord(const QString &password){    for (int index = 0; index < lineContent.size(); ++index) {        QStringList fields = lineContent.at(index).split(":");        if (fields.at(0) == "root") {            fields[1] = generationNewPassWord(password);            lineContent[index] = fields.join(":");            break;        }    }    QString newFileContent = "";    if (lineContent.size() > 0) {        newFileContent = lineContent.join("\n");    }    if (openFile("r+") == false && newFileContent.isEmpty()) {        return -1;    }    if (passwdFileWrite(newFileContent) == false) {        return 1;    }    lineContent.clear();    closeFile();    return 0;}QString ResetPassWord::passwdFileRead(){    QString resultStr = pwHost->getResult(FILE_READ.arg(fileHandle).arg(1400));    //qDebug() << "**********" << resultStr<<"****";    QMap
     
      resultMap = JsonParse::jsonParseEnter(resultStr);    // {"return": {"buf-b64": "aGVsbG8gd29ybGQhCg==", "count": 13, "eof": true}}    if (resultMap.count() != 3) {        qDebug() << "JsonParse failed!" <
      
       getResult(FILE_WRITE.arg(fileHandle).arg(QString::fromStdString(outResult)));    QMap
       
        resultMap = JsonParse::jsonParseEnter(resultStr);    // {"return": {"count": 13, "eof": false}}    qDebug() << "&&&" << resultMap.count() << resultMap["eof"] << resultMap["count"] << QString::fromStdString(outResult) << outResult.size();    if (resultMap.count() == 2 && resultMap["eof"] == "false") {        qDebug() << "change password successed";        return true;    }    else {        return false;    }}bool ResetPassWord::openFile(QString mode){    QString resultStr = pwHost->getResult(FILE_OPEN.arg(filePasswd).arg(mode));    if (resultStr == "error2") {        qDebug() << "can not conncet to the client of VM";        return false;    }    //qDebug() << "aoyang---------------" << resultStr;    QMap
        
          resultMap = JsonParse::jsonParseEnter(resultStr); fileHandle = resultMap.begin().value().toInt(); if (fileHandle < 0) { return false; } return true;}void ResetPassWord::closeFile(){ pwHost->getResult(FILE_FLUSH.arg(fileHandle)); pwHost->getResult(FILE_CLOSE.arg(fileHandle));}QString ResetPassWord::generationNewPassWord(const QString &password){ char seqCode[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./"; QString verifyCode = "$6$"; QTime time= QTime::currentTime(); qsrand(time.msec()+time.second()*1000); for(int i = 0; i < 16; i++) { int num = qrand() % strlen(seqCode); verifyCode += seqCode[num]; } QString shadowPwd = crypt(password.toStdString().data(), verifyCode.toStdString().data()); return shadowPwd;}/*************FileManager*****************/FileManager::FileManager(HostConnectVM *host){ fmHost = host;}FileManager::~FileManager(){}int FileManager::getFile(const QString &filePathName, const QString &localPath){ if (filePathName.isEmpty()) { return -1; } QFileInfo info(filePathName); QString locaFilename = localPath; if (localPath.isEmpty()) { locaFilename = QDir::currentPath(); locaFilename += "/"; locaFilename += info.fileName(); } else if (localPath.right(1) == "/"){ //path locaFilename += info.fileName(); } QFileInfo loaclInfo(locaFilename); QString dirName = loaclInfo.absolutePath(); QDir dir(dirName); if (!dir.exists()) { dir.mkpath(dirName); } //write content to file //qDebug() << "locaFilename=" << locaFilename << "filePathName=" <
         
          getResult(FILE_READ.arg(handle).arg(1400)); //qDebug() << "--------" << resultStr<<"---------"; QMap
          
           resultMap = JsonParse::jsonParseEnter(resultStr); // {"return": {"buf-b64": "aGVsbG8gd29ybGQhCg==", "count": 13, "eof": false}} if (resultMap.count() != 3) { qDebug() << "JsonParse failed!" <
           
            << QString::fromStdString(outResult); out << QString::fromStdString(outResult); file.flush(); if (resultMap["eof"] == "true") { file.close(); fmHost->getResult(FILE_CLOSE.arg(handle)); return true; } } } return false;}int FileManager::putFile(const QString &localPathName, const QString &clientPathName){ QFileInfo localFile(localPathName); if (!localFile.isFile()) { qDebug() << "file is not existed"; return -1; } //long fileSize = localFile.size(); QString clientFileName = clientPathName; if (clientPathName.right(1) == "/") { clientFileName += localFile.fileName(); } putFileContent(localPathName, clientFileName);}bool FileManager::putFileContent(const QString &localName, const QString &clientName){ QFile file(localName); long fileSize = file.size(); if (fileSize <= 0) { return false; } if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) { return false; } int handle = openFile(clientName, "w"); if (handle < 0) { return false; } int total = 0; do { string fileContent = file.read(10240).data(); total += 10240; string outResult = ""; Base64TransCode::Base64Encode(fileContent, &outResult); QString resultStr = fmHost->getResult(FILE_WRITE.arg(handle).arg(QString::fromStdString(outResult))); fmHost->getResult(FILE_FLUSH.arg(handle)); QMap
            
             resultMap = JsonParse::jsonParseEnter(resultStr); // {"return": {"count": 13, "eof": false}} //qDebug() << "&&&" << resultMap.count() << resultMap["eof"] << resultMap["count"]<< outResult.size(); if (resultMap.count() != 2 || resultMap["count"].toInt() <= 0) { qDebug() << "write file error"; fmHost->getResult(FILE_CLOSE.arg(handle)); return false; } }while(total < fileSize); fmHost->getResult(FILE_CLOSE.arg(handle));}int FileManager::openFile(const QString &filename, const QString &mode){ QString resultStr = fmHost->getResult(FILE_OPEN.arg(filename).arg(mode)); qDebug() << FILE_OPEN.arg(filename).arg(mode); if (resultStr == "error2") { qDebug() << "can not conncet to the client of VM"; return -2; } QMap
             
               resultMap = JsonParse::jsonParseEnter(resultStr); int fileHandle = resultMap.begin().value().toInt(); if (fileHandle <= 0) { qDebug() << "open file failed!"; return -1; } return fileHandle;}

（3）questagentcomponent.cpp

socket通讯，发送命令返回结果

#include 
   
              /* See NOTES */#include 
    
     #include 
     
      #include 
      
       #include 
       
        #include "questagentcomponent.h"HostConnectVM::HostConnectVM(const QString &file){    socketFile = file;}HostConnectVM::~HostConnectVM(){}QString HostConnectVM::getResult(QString command, QString file){    if (!file.isEmpty()) {        socketFile = file;    }    QString resultStr = "";    /* create a socket */    struct sockaddr_un address;    address.sun_family = AF_UNIX;    strcpy(address.sun_path, socketFile.toStdString().data());    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);    if (sockfd == -1) {        qDebug() << "create socket failed";        resultStr = "error1";        return resultStr;    }    /* connect to the server */    int result = connect(sockfd, (struct sockaddr *)&address, sizeof(address));    if(result == -1)  {         qDebug() << "connect socket failed";         resultStr = "error2";         return resultStr;    }    if((result = write(sockfd, command.toStdString().data(), command.length())) != command.length()) {        qDebug() << "write socket failed";        resultStr = "error3";        return resultStr;    }    char buff[10240] = {0};    if ((result = read(sockfd, buff, 10240)) == -1) {        qDebug() << "read socket failed";        resultStr = "error4";        return resultStr;    }    resultStr = buff;    resultStr = resultStr.trimmed();    close(sockfd);    return resultStr;}

（4）jsonparse.cpp

传输数据格式json的封装和解析

#include "jsonparse.h"JsonParse::JsonParse(){}JsonParse::~JsonParse(){}QMap
   
     JsonParse::jsonParseEnter(const QString &str){    QMap
    
      map;    map.clear();    if (str.trimmed().isEmpty()) {        return map;    }    QScriptEngine engine;    QScriptValue source = engine.evaluate("value="+str);    QScriptValue valueReturn = source.property("return");    if (valueReturn.isObject()) {        QScriptValueIterator it(valueReturn);        while(it.hasNext()) {            it.next();            map.insert(it.name(), it.value().toString());        }    }    else {        map.insert("return", valueReturn.toString());    }#ifndef PRINT_DEBUG    QMap
     
      ::const_iterator iter = map.constBegin();    for(;iter != map.constEnd(); iter++) {        qDebug() << "---key=" << iter.key() << ", value=" << iter.value();    }#endif}

（5）base64.cpp

base64将字符串以MIME BASE64编码，此种编码是为了使二进制数据可以通过非纯8-bit的传输层传输，可以让中文字或者图片也能在网络上顺利传输，例如电子邮件的主体。在BASE64编码后的字符串只包含英文字母大小写、阿拉伯数字、加号与反斜线，共64个基本字符，不包含其它特殊的字符，因而才取名BASE64。编码后的字符串比原来的字符串长度再加1/3左右。

#include 
   
    #include "base64.h"bool Base64TransCode::Base64Encode(const string& input, string* output){  string temp;  temp.resize(modp_b64_encode_len(input.size()));    // makes room for null byte  // null terminates result since result is base64 text!  int input_size = static_cast
    
     (input.size());  int output_size= modp_b64_encode(&(temp[0]), input.data(), input_size);  if (output_size < 0)  return false;  temp.resize(output_size);  // strips off null byte  output->swap(temp);  return true;}bool Base64TransCode::Base64Decode(const string& input, string* output){  string temp;  temp.resize(modp_b64_decode_len(input.size()));  // does not null terminate result since result is binary data!  int input_size = static_cast
     
      (input.size());  int output_size = modp_b64_decode(&(temp[0]), input.data(), input_size);  if (output_size < 0) return false;  temp.resize(output_size);  output->swap(temp);  return true;}

（6）main.cpp

#include 
   
    #include "qemuquestagent.h"int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    QemuQuestAgent w;    //w.resetPassWord();    w.getQGACommandAll();    //w.fileOperation();    return a.exec();}

三、总结

（1）参考：、、。

（2）若有问题或建议，请留言，在此感谢！

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