这篇文章主要讲解了“macvtap的使用教程”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“macvtap的使用教程”吧！
kubernetes一键安装
macvtap是虚拟机网络虚拟化常用的一种技术，当然容器也可以用. MACVTAP 的实现基于传统的 MACVLAN. 和 TAP 设备一样，每一个 MACVTAP 设备拥有一个对应的 Linux 字符设备，并拥有和 TAP 设备一样的 IOCTL 接口，因此能直接被 KVM/Qemu使用，方便地完成网络数据交换工作. 引入 MACVTAP 设备的目标是：简化虚拟化环境中的交换网络，代替传统的 Linux TAP 设备加 Bridge 设备组合，同时支持新的虚拟化网络技术，如 802.1 Qbg.
如kata的虚拟化网络就用了这个技术，以下实践完就会对kata的网络原理比较清楚了，建议对照教程动手实践.
我已经做好了qemu libvirt的镜像，大家可以直接使用： 在容器中有非常多的好处，环境如果乱了可以快速恢复干净的环境。 使用设备对也可减少对宿主机网络的影响。
docker run -d --privileged -v /dev:/dev -v /home/fanux:/root --name qemu-vm fanux/libvirt:latest init
注意：
网络等操作需要容器有特权模式
tap网络需要挂载/dev目录
/home/fanux可以作为工作目录，镜像自己编写的libvirt配置等放在里面防止删除容器后丢失
由于libvirt需要systemd所以我们在容器中启动init进程
也可自己构建镜像，我提供了一个Dockerfile, -j参数根据你机器CPU来设置编译时的线程数:
FROM centos:7.6.1810 RUN yum install -y wget && wget https://download.qemu.org/qemu-4.0.0.tar.xz && \ tar xvJf qemu-4.0.0.tar.xz \ && yum install -y automake gcc-c++ gcc make autoconf libtool gtk2-devel \ && cd qemu-4.0.0 \ && ./configure \ && make -j 72 && make install \ && yum install -y bridge-utils && yum install -y net-tools tunctl iproute && yum -y install openssh-clients \ cd .. && rm qemu-4.0.0.tar.xz && rm -rf qemu-4.0.0 RUN yum install -y libvirt virt-manager gustfish openssh-clients
进入容器
[root@compute84 libvirt]# docker exec -it qemu-vm bash bash-4.2# cd bash-4.2# ls CentOS-7-x86_64-GenericCloud.qcow2 centos.qcow2 image nohup.out start.sh vm3.xml CentOS-7-x86_64-Minimal-1810.iso cloud-init-start.sh kernel qemu vm.xml Fedora-Cloud-Base-30-1.2.x86_64.qcow2 destroy.sh libvirt run.sh vm2.xml
下载虚拟机镜像：
openstack已经提供很多已经装过cloud-init的镜像，地址： https://docs.openstack.org/image-guide/obtain-images.html
我用的一个比较新的centos的qcow2格式镜像：
wget http://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud-1905.qcow2
修改虚拟机root密码：
virt-customize -a CentOS-7-x86_64-GenericCloud.qcow2 --root-password password:coolpass
查看容器网络信息：
bash-4.2# systemctl start libvirtd bash-4.2# ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 52:54:00:c6:59:47 brd ff:ff:ff:ff:ff:ff inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0 valid_lft forever preferred_lft forever 3: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr0 state DOWN group default qlen 1000 link/ether 52:54:00:c6:59:47 brd ff:ff:ff:ff:ff:ff 1310: eth0@if1311: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0 inet 172.17.0.2/16 scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::42:acff:fe11:2/64 scope link valid_lft forever preferred_lft forever
1,2,3是libvirt创建的可以忽略，最主要是eth0
vm3.xml:
<domain type='kvm'> <name>vm3</name> <memory unit='MiB'>2048</memory> <currentMemory unit='MiB'>2048</currentMemory> <os> <type arch='x86_64'>hvm</type> <boot dev='hd'/> </os> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>destroy</on_crash> <devices> <emulator>/usr/local/bin/qemu-system-x86_64</emulator> <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/root/CentOS-7-x86_64-GenericCloud.qcow2'/> <target dev='vda' bus='virtio'/> </disk> <interface type='direct'> <source dev='eth0' mode='bridge' /> <model type='virtio' /> <driver name='vhost' /> </interface> <serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target type='serial' port='0'/> </console> </devices> </domain>
这里配置正确镜像地址，interface的地方是macvtap相关的配置。
bash-4.2# virsh define vm3.xml Domain vm3 defined from vm3.xml bash-4.2# virsh start vm3 Domain vm3 started
启动完后就可以看到macvtap设备被创建出来了
bash-4.2# ip addr 7: macvtap0@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 500 link/ether 52:54:00:56:e4:20 brd ff:ff:ff:ff:ff:ff inet6 fe80::5054:ff:fe56:e420/64 scope link valid_lft forever preferred_lft forever
进入到虚拟机：
virsh console vm3
如果卡在这一步：
A start job is running for LSB: Bri... networking cloud-init[2253]: 2019-06-27 08:37:09,971 - url_helper.py[WARNING]: Calling 'http://192.168.122.1/latest/meta-data/instance-id' failed [87/120s]: request error
等它超时就好，因为macvtap时我们需要进入虚拟机去配置网络。 然后就可以进入虚拟机了：
CentOS Linux 7 (Core) Kernel 3.10.0-957.1.3.el7.x86_64 on an x86_64 localhost login: root Password: Last login: Thu Jun 27 07:19:32 from gateway
密码是我们上面设置的镜像密码：coolpass
[root@localhost ~]# ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:56:e4:20 brd ff:ff:ff:ff:ff:ff inet6 fe80::5054:ff:fe56:e420/64 scope link valid_lft forever preferred_lft forever
[root@localhost ~]# ip addr add 172.17.0.2/16 dev eth0 [root@localhost ~]# ip route add default via 172.17.0.1 dev eth0 [root@localhost ~]# ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:56:e4:20 brd ff:ff:ff:ff:ff:ff inet 172.17.0.2/16 scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::5054:ff:fe56:e420/64 scope link valid_lft forever preferred_lft forever [root@localhost ~]# ip route default via 172.17.0.1 dev eth0 172.17.0.0/16 dev eth0 proto kernel scope link src 172.17.0.2 [root@localhost ~]# ping 172.17.0.1 PING 172.17.0.1 (172.17.0.1) 56(84) bytes of data. 64 bytes from 172.17.0.1: icmp_seq=1 ttl=64 time=0.622 ms 64 bytes from 172.17.0.1: icmp_seq=2 ttl=64 time=0.194 ms
配置完后就可以ping通网关了。
这个不改可能会导致ssh时非常慢：
[root@localhost ~]# cat /etc/resolv.conf ; Created by cloud-init on instance boot automatically, do not edit. ; ; generated by /usr/sbin/dhclient-script nameserver 114.114.114.114
修改/etc/ssh/sshd-config文件，将其中的PermitRootLogin no修改为yes，PubkeyAuthentication yes修改为no，AuthorizedKeysFile .ssh/authorized_keys前面加上#屏蔽掉，PasswordAuthentication no修改为yes就可以了。
docker run --rm -it fanux/libvirt bash [root@ee18547e9ed2 /]# ssh root@172.17.0.2 ssh: connect to host 172.17.0.2 port 22: Connection refused
会发现不通, 这是因为容器里的eth0和虚拟机里的eth0都配置了相同的地址导致，只需要把容器里的eth0地址删掉即可：
bash-4.2# ip addr del 172.17.0.2/16 dev eth0
再次ssh即可进入虚拟机：
[root@ee18547e9ed2 /]# ssh root@172.17.0.2 The authenticity of host '172.17.0.2 (172.17.0.2)' can't be established. ECDSA key fingerprint is SHA256:kTk3yy8588WQHNtwpzS+h7u0W3RELWC8hJQwIwLOkdc. ECDSA key fingerprint is MD5:0c:f3:b5:69:c6:08:05:14:f8:da:42:2f:85:29:51:d0. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '172.17.0.2' (ECDSA) to the list of known hosts. root@172.17.0.2's password: Last login: Thu Jun 27 08:38:00 2019 [root@localhost ~]# ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:56:e4:20 brd ff:ff:ff:ff:ff:ff inet 172.17.0.2/16 scope global eth0 valid_lft forever preferred_lft forever inet6 fe80::5054:ff:fe56:e420/64 scope link valid_lft forever preferred_lft forever
[root@localhost ~]# ip link set eth0 address 52:54:00:56:e4:23
会发现就连不上虚拟机了
改回：
[root@localhost ~]# ip link set eth0 address 52:54:00:56:e4:20
又可正常连接了，为啥？
这是因为虚拟机的eth0的mac地址是必须与macvtap0的mac地址保持一样，原理很简单
ARP时问IP地址是172.17.0.2的机器mac地址是什么
虚拟机回了一个52:54:00:56:e4:20
macvtap0是可以理解成挂在网桥端口上的，这样就把包发给macvtap0了（因为mac地址一样,不一样就不会发给macvtap了）
macvtap0就把包丢给qemu应用进程（最终到虚拟机eth0）
以上是通过libvirt进行使用的，这样屏蔽了很多底层的细节，如果是直接使用qemu命令需要如下操作：
创建macvtap设备：
ip link add link eth0 name macvtap0 type macvtap mode bridge ip link set macvtap0 address 1a:46:0b:ca:bc:7b up bash-4.2# cat /sys/class/net/macvtap0/ifindex # 对应下面命令的/dev/tap2 2 bash-4.2# cat /sys/class/net/macvtap0/address # 与qemu mac地址配置一致 1a:46:0b:ca:bc:7b
启动qemu,然后虚拟机里面的地址配置同libvirt，可以通过vnc客户端（vnc viewer）进入虚拟机配置，不在赘述:
bash-4.2# qemu-system-x86_64 -enable-kvm /root/CentOS-7-x86_64-GenericCloud.qcow2\ -netdev tap,fd=30,id=hostnet0,vhost=on,vhostfd=4 30<>/dev/tap2 4<>/dev/vhost-net \ -device virtio-net-pci,netdev=hostnet0,id=net0,mac=1a:46:0b:ca:bc:7b \ -monitor telnet:127.0.0.1:5801,server,nowait VNC server running on ::1:5900
上文提到，通过macvtap技术配置虚拟机网卡地址是需要进入虚拟机配置的, 然而我们实现一个虚拟机管理系统时显然不会手动进入去配置，这就需要cloud-init了
它可以帮助我们在虚拟机启动时配置虚拟机，如配置密码，配置网络，执行命令和写一些文件等。 先创建一个user-data文件，里面内容如下：
#cloud-config write_files: - content: | DEVICE=eth0 ONBOOT=yes TYPE=Ethernet USERCTL=no IPADDR=172.17.0.2 NETMASK=255.255.0.0 GATEWAY=172.17.0.1 BOOTPROTO=static DNS1=172.17.0.1 ONBOOT=yes path: /etc/sysconfig/network-scripts/ifcfg-eth0 runcmd: - systemctl start network groups: - centos: [root] - cloud-users ssh_pwauth: yes chpasswd: expire: false list: | user1:222222 root:333333
创建cloud-init镜像文件
yum install -y cloud-utils cloud-localds my-seed.img user-data
libvirt中使用该镜像
<disk type='file' device='disk'> <driver name='qemu' type='raw'/> <source file='/root/my-seed.img'/> <target dev='vdb' bus='virtio'/> </disk>
为了防止cloud-init走网络获取metadata，因为网卡没设置好所以会卡住五分钟，我们直接把网络获取metadata禁止掉：
vi /etc/cloud/cloud.cfg.d/05_logging.cfg
加上：
network: config: disabled
然后启动虚拟机即可
Inappropriate ioctl for device
qemu-system-x86_64: -net tap,fd=5: TUNGETIFF ioctl() failed: Inappropriate ioctl for device TUNSETOFFLOAD ioctl() failed: Inappropriate ioctl for device
因为容器没有挂载/dev目录
KVM bios被禁
[root@helix105 ~]# docker run busybox uname -a Could not access KVM kernel module: No such file or directory qemu-lite-system-x86_64: failed to initialize KVM: No such file or directory /usr/bin/docker-current: Error response from daemon: oci runtime error: Unable to launch /usr/bin/qemu-lite-system-x86_64: exit status 1. ERRO[0001] error getting events from daemon: net/http: request canceled [root@helix105 ~]# lsmod |grep kvm kvm 598016 0 irqbypass 16384 1 kvm [root@helix105 ~]# modprobe kvm-intel modprobe: ERROR: could not insert 'kvm_intel': Operation not supported You have mail in /var/spool/mail/root [root@helix105 ~]# dmesg |grep kvm [ 8.239309] kvm: disabled by bios
这个要进bios打开
KVM: Permission denied
bash-4.2# virsh start vm_name1 error: Failed to start domain vm_name1 error: internal error: qemu unexpectedly closed the monitor: Could not access KVM kernel module: Permission denied 2019-06-20T07:26:33.304320Z qemu-system-x86_64: failed to initialize KVM: Permission denied
解决办法：
#chown root:kvm /dev/kvm 修改/etc/libvirt/qemu.conf， #user="root" user="root" #group="root" group="root" 重启服务 #service libvirtd restart，问题解决了
感谢各位的阅读，以上就是“macvtap的使用教程”的内容了，经过本文的学习后，相信大家对macvtap的使用教程这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是亿速云，小编将为大家推送更多相关知识点的文章，欢迎关注！
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