通过网络连接到QEMU monitor

在我的KVM书中，关于QEMU监控器（monitor）的使用还是讲了不少东西的，不过，翻看以前收藏的一篇文章，发现其中提到的通过网络访问QEMU monitor的方法是没有在书中提及的。所以，在这里简单介绍一下吧，也是给自己留个记忆。（如果--仅仅是如果，有再版的话，可以考虑加上一两页来讲个东东。）

1. QEMU monitor支持远程telnet访问：

[root@kvm-host ~]# qemu-system-x86_64 -enable-kvm -smp 2 -m 1024 vm2.img -monitor telnet:10.1.77.82:4444,server,nowait

1	[root@kvm-host ~]# qemu-system-x86_64 -enable-kvm -smp 2 -m 1024 vm2.img -monitor telnet:10.1.77.82:4444,server,nowait

关于这里-monitor的选项，做如下说明：

    tcp – raw tcp sockets  #下面第2点，我的举例是RAW TCP socket
    telnet – the telnet protocol is used instead of raw tcp sockets. This is the preferred option over tcp as you can break out of the monitor using Ctrl-] then typing quit. You can’t break out of the monitor like this after connecting with the raw socket option
    10.1.77.82 – Listen on this host/IP only. You can use 127.0.0.1 if you want to only allow connections locally. If you want to listen on any ip address on the server, just leave this blank so you end up with two consecutive colons ie “::” .
    4444 – port number to listen on.
    server – listening in server mode
    nowait – qemu will wait for a client socket application to connect to the port before continuing unless this option is used. In most cases you’ll want to use the nowait option.

tcp – raw tcp sockets #下面第2点，我的举例是RAW TCP socket

telnet – the telnet protocol is used instead of raw tcp sockets. This is the preferred option over tcp as you can break out of the monitor using Ctrl-] then typing quit. You can’t break out of the monitor like this after connecting with the raw socket option

10.1.77.82 – Listen on this host/IP only. You can use 127.0.0.1 if you want to only allow connections locally. If you want to listen on any ip address on the server, just leave this blank so you end up with two consecutive colons ie “::” .

4444 – port number to listen on.

server – listening in server mode

nowait – qemu will wait for a client socket application to connect to the port before continuing unless this option is used. In most cases you’ll want to use the nowait option.

通过telnet连接到远程的QEMU monitor上：

jay@jay-linux:~$ telnet 10.1.77.82 4444
Trying 10.1.77.82...
Connected to 10.1.77.82.
Escape character is '^]'.
QEMU 1.7.50 monitor - type 'help' for more information
(qemu) info kvm
kvm support: enabled
(qemu) info status
VM status: running
(qemu) help migrate
migrate [-d] [-b] [-i] uri -- migrate to URI (using -d to not wait for completion)
                         -b for migration without shared storage with full copy of disk
                         -i for migration without shared storage with incremental copy of disk (base image shared between src and destination)
(qemu) ctrl + ] （断掉telnet连接）
telnet> quit      （退出telnet）
Connection closed.

jay@jay-linux:~$ telnet 10.1.77.82 4444

Trying 10.1.77.82...

Connected to 10.1.77.82.

Escape character is '^]'.

QEMU 1.7.50 monitor - type 'help' for more information

(qemu) info kvm

kvm support: enabled

(qemu) info status

VM status: running

(qemu) help migrate

migrate [-d] [-b] [-i] uri -- migrate to URI (using -d to not wait for completion)

-b for migration without shared storage with full copy of disk

-i for migration without shared storage with incremental copy of disk (base image shared between src and destination)

(qemu) ctrl + ] （断掉telnet连接）

telnet> quit （退出telnet）

Connection closed.

2. QEMU monitor支持RAW socket的远程访问：

[root@kvm-host ~]# qemu-system-x86_64 -enable-kvm -smp 2 -m 1024 vm2.img -monitor tcp:10.1.77.82:4444,server,nowait

1	[root@kvm-host ~]# qemu-system-x86_64 -enable-kvm -smp 2 -m 1024 vm2.img -monitor tcp:10.1.77.82:4444,server,nowait

可以使用netcat去连接这个socket：

jay@jay-linux:~$ nc 10.1.77.82 4444
QEMU 1.7.50 monitor - type 'help' for more information
(qemu) info kvm
info kvm
kvm support: enabled
(qemu) ^C

jay@jay-linux:~$ nc 10.1.77.82 4444

QEMU 1.7.50 monitor - type 'help' for more information

(qemu) info kvm

info kvm

kvm support: enabled

(qemu) ^C

自己写了个socket程序示例如连接monitor，效果如下：

jay@jay-linux:~/workspace/c-cpp.git/c2013$ ./monitor_client
sending command 'info kvm
' to remote qemu monitor
output from qemu monitor: QEMU 1.7.50 monitor - type 'help' for more information
 ��,�
output from qemu monitor: (qemu) info kvm
kvm support: enabled
(qemu)

jay@jay-linux:~/workspace/c-cpp.git/c2013$ ./monitor_client

sending command 'info kvm

' to remote qemu monitor

output from qemu monitor: QEMU 1.7.50 monitor - type 'help' for more information

��,�

output from qemu monitor: (qemu) info kvm

kvm support: enabled

(qemu)

上面那个连接monitor的socket程序示例为：
https://github.com/smilejay/c-cpp/blob/master/c2013/socket_qemu_monitor_client.c

/* socket_qemu_monitor_clinet.c
* Connect to remote QEMU monitor socket and sending a command to the monitor.
* author: Jay <smile665@gmail.com>
*/

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[])
{
        int sockfd;
        int len;
        struct sockaddr_in address;
        int result;
        char *cmd = "info kvm\n";
        char output[200];

        /* Create a socket for the client. */
        sockfd = socket(AF_INET, SOCK_STREAM, 0);

        /* Name the socket, as agreed with the server. */
        address.sin_family = AF_INET;
        address.sin_addr.s_addr = inet_addr("10.1.77.82");
        address.sin_port = htons(4444);
        len = sizeof(address);

        /* Now connect our socket to the server's socket. */
        result = connect(sockfd, (struct sockaddr *)&address, len);

        if(result == -1) {
                perror("oops: socket connetion failed.");
                exit(1);
        }

        /* We can now read/write via sockfd. */
        printf("sending command '%s' to remote qemu monitor\n", cmd);
        write(sockfd, cmd, strlen(cmd));
        read(sockfd, output, sizeof(output));
        printf("output from qemu monitor: %s\n", output);
        read(sockfd, output, sizeof(output));
        printf("output from qemu monitor: %s\n", output);
        close(sockfd);
        exit(0);
}

/* socket_qemu_monitor_clinet.c

* Connect to remote QEMU monitor socket and sending a command to the monitor.

* author: Jay <smile665@gmail.com>

#include <sys/types.h>

#include <sys/socket.h>

#include <stdio.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <unistd.h>

#include <stdlib.h>

#include <string.h>

int main(int argc, char *argv[])

{

int sockfd;

int len;

struct sockaddr_in address;

int result;

char *cmd = "info kvm\n";

char output[200];

/* Create a socket for the client. */

sockfd = socket(AF_INET, SOCK_STREAM, 0);

/* Name the socket, as agreed with the server. */

address.sin_family = AF_INET;

address.sin_addr.s_addr = inet_addr("10.1.77.82");

address.sin_port = htons(4444);

len = sizeof(address);

/* Now connect our socket to the server's socket. */

result = connect(sockfd, (struct sockaddr *)&address, len);

if(result == -1) {

perror("oops: socket connetion failed.");

exit(1);

}

/* We can now read/write via sockfd. */

printf("sending command '%s' to remote qemu monitor\n", cmd);

write(sockfd, cmd, strlen(cmd));

read(sockfd, output, sizeof(output));

printf("output from qemu monitor: %s\n", output);

read(sockfd, output, sizeof(output));

printf("output from qemu monitor: %s\n", output);

close(sockfd);

exit(0);

}

参考资料：
http://www.linux-kvm.com/content/two-ways-access-your-virtual-machine-monitor-across-network

7 Comments

回复

03/27/2016
lix

您好，
最近在研究kvm虚拟机迁移。在迁移过程中需要升级qemu，按照网上的方法下载最新版本qemu，然后进行编译、安装。安装成功了，但是发现原来的qemu还存在，libvirt和virsh都使用原来的qemu版本。不知道在哪个地方能修改libvirt条用qemu的地方。之前看到网络一些资料说libvirt会自行检测固定目录，如果存在qemu就是使用它。
新版本：[root@Vm-host5 ~]# /usr/local/bin/qemu-system-x86_64 --version
QEMU emulator version 2.5.0, Copyright (c) 2003-2008 Fabrice Bellard
旧版本：[root@Vm-host5 ~]# /usr/libexec/qemu-kvm --version
QEMU PC emulator version 0.12.1 (qemu-kvm-0.12.1.2-2.479.el6_7.4), Copyright (c) 2003-2008 Fabrice Bellard
也按照网上一做法：创建一个软连接/usr/local/bin/qemu-system-x86_64 到/usr/libexec/qemu-kvm。创建了软连接，提示说：ln: 创建符号链接 "/usr/libexec/qemu-kvm": 文件已存在。是否我需要删除/usr/libexec/qemu-kvm？？不知道有什么方法替换掉原来的qemu?
我是菜鸟，希望您解答我的疑问，感激不尽！
回复

03/27/2016
lix

我把/usr/libexec/qemu-kvm删除，然后再把/usr/local/bin/qemu-system-x86_64 连接到/usr/libexec/qemu-kvm去了。我不太能确定这样libvirt是否能调用的我最新版本的qemu。
- 回复
  
  03/28/2016
  master
  
  你这样做也是可以的；不过更加专业的做法是，在guest的xml配置文件中修改 emulator 这个标签行以便指定自己的qemu的位置。
回复

06/24/2016
十一

博主您好，我想用qemu-system命令行启动客户机，想要设置virtio网卡驱动的队列对数为2，
命令是这样的：
qemu-system-x86_64 ubuntu.img -smp 4 -m 2048 -net nic,model=virtio -net tap,vhost=on,queues=2

却总提示‘queues’是invalid parameter
问题出在哪里呢
回复

06/24/2016
十一

博主您好，我想用qemu-system命令行启动客户机，想要设置virtio网卡驱动的队列对数为2，
命令是这样的：
qemu-system-x86_64 ubuntu.img -smp 4 -m 2048 -net nic,model=virtio -net tap,vhost=on,queues=2

却总提示‘queues’是invalid parameter
- 回复
  
  07/02/2016
  master
  
  可能是你的qemu版本太老了的升级到2.x之类的试试
  另外，这里的配置和你的有所差异，看下：http://www.linux-kvm.org/page/Multiqueue#Enable_MQ_feature
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