vimer linux kernel 爱好者

用libvirt安装debian

2017-06-06
tools

这篇文章主要聚焦于debian系统，其他的linux发行版的用法应该是一致的。

Setup

You start by installing the needed tools, So, on my debian:

sudo apt-get install libvirt-dev virtinst libvirt-daemon libvirt-daemon-system

如果没有找到相应的软件包，你可以尝试一下apt-cache命令。 (If you cant found these softwares, you can try it : apt-cache) 系统提示你缺少什么软件就安装什么软件。

sudo apt-cache search libvirt

你还可以使用通配符进行模糊查找。 (You can fuzzy search with wildcard)

Then you got a libvirtd process running on your machine:

yubo@debian:~/git$ sudo ps u -C libvirtd
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root     4470  1.4  0.7 787416 30212 ?        Ssl  20:38   0:00 /usr/sbin/libvi

The role of libvirtd is quite important. It takes care of managing the VMSrunning on your host.You can control it with command virsh.

First few steps with libvirt

Before anything else, you should know that libvirt and virsh not only allow you to control VMs running on your own system, but can control VMs running on the remote systems or a cluster of physical machines. Every time you use virsh, With qemu,you need type it looks like:

qemu://xxx/system
qemu://xxx/session

I will introduce more details about virsh in another post,now i am focus on the libvirt-vms.

Managing system VMS

Here, libvirtd is listening the command send to /var/run/libvirt,so you may add a credential user for libvirt, and you have opportunity to write socket, which needs a user to belong to the libvirt group.

If you edit /etc/libvirt/libvirtd.conf, you can configure libvirt to wait for a commands using a variety of different mechanisms, including for example SSL encrypted TCP sockets.

yubo@debian:~/git$ sudo usermod -a -G libvirt yubo

Add my user name into libvirt group.

Defining a network

yubo@debian:~/git$ virsh -c qemu:///system net-list
 Name                 State      Autostart     Persistent
 ----------------------------------------------------------

This means that there are no active virtual networks, Try one more time adding --all:

yubo@debian:~/git$ virsh -c qemu:///system net-list --all
 Name                 State      Autostart     Persistent
 ----------------------------------------------------------
  default              inactive   no            yes

note

Now your network’s is default.

And notice the default network, If you want to inspect or change the configure file of the network, you can use either net-dumpxml or net-edit


h -c qemu:///system net-dumpxml default
<network>
  <name>default</name>
  <uuid>e46e2c1b-5263-4428-b8fc-bfa4805a2ebc</uuid>
  <forward mode='nat'/>
  <bridge name='virbr0' stp='on' delay='0'/>
  <mac address='52:54:00:34:36:d3'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
	<dhcp>
	  <range start='192.168.122.2' end='192.168.122.254'/>
	</dhcp>
  </ip>
</network>

I guess you could understand what is meaning above.Now your VM bridge name is virbbr0…

You can configure networking in many different ways, with nat, with bridging,with simple gateway fowarding… You can find all parameters on the page.

And you can change the definition by using net-edit.

net-undefine default # forever eliminate the default network
net-define file.xml #to define a new network starting from an .xml file
#you can
virsh ... net-dumpxml default > file.xml
then edit and then
virsh ... net-define file.xml

Starting and stopping networks

net-start default, to start the named default network net-destory default, to stop the named defaultnetwork,with the ability of starting it again in the future.

net-autostart default, to automatically start the default network at boot.

yubo@debian:~/git$ virsh -c qemu:///system net-start default
Network default started

yubo@debian:~/git$ ps aux | grep libvirt

root      4470  0.0  0.7 1377240 30292 ?     Ssl  20:38   0:00 /usr/sbi..
nobody    5155  0.0  0.0  52228   408 ?     S    21:40   0:00 /usr/sb..
root      5156  0.0  0.0  52200   408 ?  S   21:40   0:00 /usr/sbin/dnsmasq
----------------
yubo@debian:~/git$ sudo netstat -nulp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address  Foreign Address State  PID/Program name
udp   0       0    192.168.122.1:53      0.0.0.0:*         5155/dnsmasq
udp  0        0     0.0.0.0:67           0.0.0.0:*          5155/dnsmasq
-----------------
yubo@debian:~/git$ sudo netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address  State PID/Program name
tcp   0      0      192.168.122.1:53   0.0.0.0:*   LISTEN     5155/dnsmasq
tcp   0      0       0.0.0.0:22        0.0.0.0:*   LISTEN      546/sshd

libvirt started dnsmasq, which is a simple dhcp server with ability to also provide DNS.So you can try:

yubo@debian:~/git$ ip address show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    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: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP group default qlen 1000
      link/ether 94:c6:91:04:e6:91 brd ff:ff:ff:ff:ff:ff
      inet 222.195.244.235/24 brd 222.195.244.255 scope global dynamic
      enp1s0
      valid_lft 2670sec preferred_lft 2670sec
     inet6 fe80::96c6:91ff:fe04:e691/64 scope link
	            valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue
state DOWN group default qlen 1000
   link/ether 52:54:00:34:36:d3 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
4: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master
virbr0 state DOWN group default qlen 1000
   link/ether 52:54:00:34:36:d3 brd ff:ff:ff:ff:ff:ff

you can use iptables to see what happened:

sudo iptables -nvL
&&
sudo iptables -t nat -nvL

Managing storage

Now we have a network running for our VMs,we need to worry about storage.This is similar to lvm, On this post, i just dedicated a directory to storing images and volums.

But, you should mdkir needed dir with

sudo mkdir -p /opt/kvms/pools/devel

and try it:

yubo@debian:~$ virsh -c qemu:///system \
		> pool-define-as devel \
		> dir --target /opt/kvms/pools/devel
		Pool devel defined

Here, we create a pool called devel in a directory , we can see this pool with:

yubo@debian:~$ virsh -c qemu:///system pool-list --all
 Name                 State      Autostart
 -------------------------------------------
  devel                inactive   no

--all as before, now we need to start it automatically with command:

yubo@debian:~$ virsh -c qemu:///system pool-autostart devel
Pool devel marked as autostarted

and start it with(must):

yubo@debian:~$ virsh -c qemu:///system pool-start devel

And you can see it again:

yubo@debian:~$ virsh -c qemu:///system pool-list --all
 Name                 State      Autostart
 -------------------------------------------
  devel                active     yes

To create and manage volumes, you can use vol-create,vol-delete,vol-resize,all the vol-* can be used.

For examole:

yubo@debian:~$ virsh -c qemu:///system vol-list devel
 Name                 Path
 ------------------------------------------------------

Installing a virtual machine

With virt-install

yubo@debian:~$ virt-install -n debian-9 --ram 2048 --vcpus=2 \
--cpu=host -c ~/software/debian-9.1.0-amd64-xfce-CD-1.iso \
--os-type=linux --os-variant=debian \
--disk=pool=devel,size=10,format=qcow2 \
-w network=default --graphics=vnc

You must use sudo command to execute the command,next, you will enter into linux’s installing procession.

-n just a name.

-c is your debian-iso where it is located. Remember here, you just define a pool named devel, however, you not have ‘create it’

--disk=pool=devel,size=10,format=qcow2 means it have 10GB space disk to support your VMs.

virt-install version 1.5.1报错debian没有在它的安装字典中，可以尝试着使用debian9.

how to delete a vm

sudo virt-install destroy domain
sudo virt-install undefine domain

Managing a vitual machine

This is my first wrong step to try it.I missed it.

After installing VMs, you would better to use virt-viewer to start it.

Frist,you can start it with virsh:

virsh start my-vms #my vms-name is debian-9 or:
virsh autostart my-vms # debian-9.

So, you type virsh into virsh’s world.

yubo@debian:~$ sudo virsh
[sudo] yubo 的密码：
Welcome to virsh, the virtualization interactive terminal.

Type:  'help' for help with commands
       'quit' to quit

       virsh # list
        Id    Name                           State
	----------------------------------------------------
	 8     debian-9                       running

Remember, you use it with sudo.Here, you can see your vms’s id is 8,

how to start vm with virsh

Again, your vm-id is 8,so next:

sudo virt-viewer --connect qemu:///system 8

Congratulations! Enjoy it:)

后记

For example, when you in trouble reboot the virtual machine,how to do? In my case, after shutdown the system installed, now i want to reboot, But, the libvirt warn me: failed to match domain ““.I don’t’ know to do. Until i have googled: first, use define to edit the configure file with XML type.Yes, when you installed a system, you will get a XML file in /etc/libvirt/qemu/(or somewhere). My way to slove the problem is cp the xml file to a directory and then sudo virsh define xx.xml.If get any errors you can disappear it according to hints.

I will post a new blog to show how to resize the pool size in KVMS.See you!

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