Difference between revisions of "KVM: Installation and operation"

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(Created page with "===== Check CPU supports KVM ===== <syntaxhighlight> egrep '(vmx|svm)' --color=always /proc/cpuinfo </syntaxhighlight> ===== Install KVM ===== <syntaxhighlight> # on RHEL 5 yum install virt-viewer virt-manag...")
 
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===== Check CPU supports KVM =====
+
== Check CPU supports KVM ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
egrep '(vmx|svm)' --color=always /proc/cpuinfo
 
egrep '(vmx|svm)' --color=always /proc/cpuinfo
 
</syntaxhighlight>
 
</syntaxhighlight>
  
−
===== Install KVM =====
+
== Install KVM ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
# on RHEL 5
 
# on RHEL 5
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</syntaxhighlight>
 
</syntaxhighlight>
  
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===== Install the modules =====
+
== Install the modules ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
modprobe kvm-intel
 
modprobe kvm-intel
 
</syntaxhighlight>
 
</syntaxhighlight>
  
−
===== Start libvirtd =====
+
== Start libvirtd ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
/etc/init.d/libvirtd restart
 
/etc/init.d/libvirtd restart
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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===== Load up virtual manager =====
+
== Load up virtual manager ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
virt-manager
 
virt-manager
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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===== Setup Bridged Networking =====
+
== Setup Bridged Networking ==
 
By Default KVM uses NAT (hosts can see outside world but world cannot see the hosts). To setup bridged networking:
 
By Default KVM uses NAT (hosts can see outside world but world cannot see the hosts). To setup bridged networking:
  
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                                                         vnet0
 
                                                         vnet0
  
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===== Create the image file =====
+
== Create the image file ==
 
In RHEL6, use virt-install: (dont use any files in /root)
 
In RHEL6, use virt-install: (dont use any files in /root)
 
<syntaxhighlight>
 
<syntaxhighlight>
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* Change CDs using '''virt-manger''' -> Open Guest -> Show Virtual Hardware -> CDROM
 
* Change CDs using '''virt-manger''' -> Open Guest -> Show Virtual Hardware -> CDROM
  
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===== Start qemu =====
+
== Start qemu ==
 
<syntaxhighlight>
 
<syntaxhighlight>
 
/usr/libexec/qemu-kvm -hda vig_xp.img  -cdrom vig_xp.iso -m 512 -boot d
 
/usr/libexec/qemu-kvm -hda vig_xp.img  -cdrom vig_xp.iso -m 512 -boot d
−
</syntaxhighlight>
 
−
 
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===== Other Handy Bits =====
 
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====== VNC / Args ======
 
−
<syntaxhighlight>
 
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CLI Args:
 
−
-alt-grab - makes ctrl+alt+shift the key escape rather than ctrl+alt (which makes it impossible for windows logins)
 
−
on vncviewer, you can also hit f8 to bring up a menu which will allow
 
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-smp n (number of cores to allocate)
 
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-m 8192 (amount of memory to give the machine)
 
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-net nic -net nic (give the system two nics)
 
−
</syntaxhighlight>
 
−
 
−
====== Mounting NFS in VM ======
 
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ERROR: mountd: refused mount nfs illegal port
 
−
 
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In case you’re getting error while mounting a nfs share, and logs on server showing:
 
−
<syntaxhighlight>
 
−
Mar 24 10:44:57 localhost mountd[8344]: refused mount request from 192.168.1.2 for /dump (/dump): illegal port 52213
 
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</syntaxhighlight>
 
−
 
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Add insecure option in your exports file:
 
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<syntaxhighlight>
 
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    /dump  *(ro,sync,no_root_squash,insecure)
 
−
 
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    # And do
 
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    exportfs -r  # or reload/restart nfs service.
 
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</syntaxhighlight>
 
−
 
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====== Grow a KVM Disk Image (RAW) ======
 
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E.G to grow a KVM image by 10G (Perhaps this could be a hell of a lot easier with LVM)
 
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* Create additional space as a raw qemu-img
 
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* cat the two files together
 
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* Boot gparted-live to resize partitions/filesystem
 
−
<syntaxhighlight>
 
−
[root@kvm vm]$ qemu-img create -f raw guest1-rhel6-64-largerdisk 10G
 
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Formatting 'guest1-rhel6-64-largerdisk', fmt=raw size=10737418240
 
−
[root@kvm vm]$ ll
 
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total 17611676
 
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-rwxrwxrwx. 1 root root 10737418240 Sep 27 14:34 guest1-rhel6-64
 
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-rwxr-xr-x  1 root root 10737418240 Sep 27 13:14 guest1-rhel6-64-clone
 
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'-rw-r--r--  1 root root 10737418240 Sep 27 14:37 guest1-rhel6-64-largerdisk'
 
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[root@kvm vm]$ cat guest1-rhel6-64 guest1-rhel6-64-largerdisk > sl6-30g-puppetcobbler.kvm
 
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[root@kvm vm]$ ll
 
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total 38583200
 
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-rwxrwxrwx. 1 root root 10737418240 Sep 27 14:34 guest1-rhel6-64
 
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-rwxr-xr-x  1 root root 10737418240 Sep 27 13:14 guest1-rhel6-64-clone
 
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-rw-r--r--  1 root root 10737418240 Sep 27 14:37 guest1-rhel6-64-largerdisk
 
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'-rw-r--r--  1 root root 21474836480 Sep 27 14:42 sl6-30g-puppetcobbler.kvm'
 
−
</syntaxhighlight>
 
−
 
−
Just as easy to convert a raw image to qcow2 and then resize that(<tt>qemu-img resize [vmname.qcow2] +100G</tt>). Use LVM as below to grow the FS.
 
−
 
−
 
−
Now boot up a ubuntu (or other) live cd (in virt-manager: add hardware -> storage -> select managed.. ->  device type -> IDE CDrom) 
 
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  Install lvm tools: apt-get install lvm2
 
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  Fdisk create new partition:
 
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  fdisk /dev/sda
 
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  delete lvm partition (d -> 2 in this instance)
 
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  create lvm partition (same cylinder start, new end pick the default which will be the last cylinder) (n -> p -> start / finish)
 
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  change type of new partition to lvm (t -> 8e)
 
−
 
−
 
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Use LVM to grow the volume
 
−
<syntaxhighlight>
 
−
root@ubuntu:~# pvdisplay /dev/sda2
 
−
  --- Physical volume ---
 
−
  PV Name              /dev/sda2
 
−
  VG Name              vg_puppetmaster
 
−
  PV Size              9.51 GiB / not usable 3.00 MiB
 
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  Allocatable          yes (but full)
 
−
  PE Size              4.00 MiB
 
−
  Total PE              2434
 
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  Free PE              0
 
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  Allocated PE          2434
 
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  PV UUID              LBxPCN-RL3d-rd7d-qEcr-M5Fq-GfMF-ttiPPd
 
−
 
 
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root@ubuntu:~# partprobe
 
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Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
 
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root@ubuntu:~# pvresize /dev/sda2
 
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  Physical volume "/dev/sda2" changed
 
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  1 physical volume(s) resized / 0 physical volume(s) not resized
 
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root@ubuntu:~# pvdisplay /dev/sda2
 
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  --- Physical volume ---
 
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  PV Name              /dev/sda2
 
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  VG Name              vg_puppetmaster
 
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  PV Size              19.50 GiB / not usable 3.46 MiB
 
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  Allocatable          yes
 
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  PE Size              4.00 MiB
 
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  Total PE              4992
 
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  Free PE              2558
 
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  Allocated PE          2434
 
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  PV UUID              LBxPCN-RL3d-rd7d-qEcr-M5Fq-GfMF-ttiPPd
 
−
 
 
−
 
−
t@ubuntu:~# vgchange -a y vg_puppetmaster
 
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  2 logical volume(s) in volume group "vg_puppetmaster" now active
 
−
root@ubuntu:~# vgdisplay vg_puppetmaster
 
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  --- Volume group ---
 
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  VG Name              vg_puppetmaster
 
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  System ID           
 
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  Format                lvm2
 
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  Metadata Areas        1
 
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  Metadata Sequence No  4
 
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  VG Access            read/write
 
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  VG Status            resizable
 
−
  MAX LV                0
 
−
  Cur LV                2
 
−
  Open LV              0
 
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  Max PV                0
 
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  Cur PV                1
 
−
  Act PV                1
 
−
  VG Size              19.50 GiB
 
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  PE Size              4.00 MiB
 
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  Total PE              4992
 
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  Alloc PE / Size      2434 / 9.51 GiB
 
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  Free  PE / Size      2558 / 9.99 GiB
 
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  VG UUID              Bu7xaM-OQrj-aZYV-gwY8-MvXg-Az1m-8wZh6p
 
−
 
 
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root@ubuntu:~# lvextend -L +10G /dev/vg_puppetmaster/lv_root
 
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  Extending logical volume lv_root to 15.57 GiB
 
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  Insufficient free space: 2560 extents needed, but only 2558 available
 
−
 
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root@ubuntu:~# lvextend -L +9.9G /dev/vg_puppetmaster/lv_root
 
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  Rounding up size to full physical extent 9.90 GiB
 
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  Extending logical volume lv_root to 15.47 GiB
 
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  Logical volume lv_root successfully resized
 
−
 
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root@ubuntu:~# resize2fs /dev/vg_puppetmaster/lv_root
 
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resize2fs 1.41.14 (22-Dec-2010)
 
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Please run 'e2fsck -f /dev/vg_puppetmaster/lv_root' first.
 
−
 
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root@ubuntu:~# e2fsck -f /dev/vg_puppetmaster/lv_root
 
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e2fsck 1.41.14 (22-Dec-2010)
 
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Pass 1: Checking inodes, blocks, and sizes
 
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Pass 2: Checking directory structure
 
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Pass 3: Checking directory connectivity
 
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Pass 4: Checking reference counts
 
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Pass 5: Checking group summary information
 
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/dev/vg_puppetmaster/lv_root: 50681/365760 files (0.1% non-contiguous), 448889/1460224 blocks
 
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root@ubuntu:~# resize2fs /dev/vg_puppetmaster/lv_root
 
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resize2fs 1.41.14 (22-Dec-2010)
 
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Resizing the filesystem on /dev/vg_puppetmaster/lv_root to 4056064 (4k) blocks.
 
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The filesystem on /dev/vg_puppetmaster/lv_root is now 4056064 blocks long.
 
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root@ubuntu:~# lvscan
 
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  ACTIVE            '/dev/vg_puppetmaster/lv_root' [15.47 GiB] inherit
 
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  ACTIVE            '/dev/vg_puppetmaster/lv_swap' [3.94 GiB] inherit
 
−
 
−
</syntaxhighlight>
 
−
 
−
====== Use old VM img with virt-manager ======
 
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You'll need to use virt-manager to import an old file. Point this towards an existing raw VM and import. Import didnt add a CD drive, so used the command:
 
−
 
−
<syntaxhighlight>   
 
−
[root@kvm vm]$ /usr/libexec/qemu-kvm -hda ./sl6-30g-puppetcobbler.kvm \
 
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      -cdrom /mnt/vstor/gparted-live/gparted-live-0.7.1-1.iso -m 512 -boot d
 
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Using CPU model "cpu64-rhel6"
 
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VNC server running on `::1:5900'
 
−
 
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# Then vmcviewer on another terminal
 
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vncviewer localhost:5900
 
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</syntaxhighlight>
 
−
 
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====== Copying VMs udev renames network ======
 
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* udev seems to be adding lines in /etc/udev/70-persistent-net.rules
 
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* Remove entries and set MAC correctly
 
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* Also had to update the files in /etc/sysconfig/network-scripts/ifcfg-eth0 to remove/change the MAC address
 
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* All this could probably have been avoided if i set the MAC correctly when setting up the machine? (not tested)
 
−
 
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====== Disable DHCP on KVM Server ======
 
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In this example i wanted to run a virtual DHCP server on the KVM system. The KVM server was getting in the way as it run a DHCP service also. To disable, remove the <tt><dhcp></tt> tags from the file <tt>/var/lib/libvirt/network/default.xml</tt>
 
−
 
−
Change from:
 
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<syntaxhighlight>
 
−
<network>
 
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  <name>default</name>
 
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  <uuid>319d4ae5-4b6e-433c-832f-ad20269ed495</uuid>
 
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  <forward mode='nat'/>
 
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  <bridge name='virbr0' stp='on' delay='0' />
 
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  <mac address='52:54:00:09:89:76'/>
 
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  <ip address='192.168.122.1' netmask='255.255.255.0'>
 
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    <dhcp>
 
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      <range start='192.168.122.2' end='192.168.122.254' />
 
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    </dhcp>
 
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  </ip>
 
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</network>
 
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</syntaxhighlight>
 
−
 
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Change to:
 
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<syntaxhighlight>
 
−
<network>
 
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  <name>default</name>
 
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  <uuid>319d4ae5-4b6e-433c-832f-ad20269ed495</uuid>
 
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  <forward mode='nat'/>
 
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  <bridge name='virbr0' stp='on' delay='0' />
 
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  <mac address='52:54:00:09:89:76'/>
 
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  <ip address='192.168.122.1' netmask='255.255.255.0'>
 
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  </ip>
 
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</network>
 
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</syntaxhighlight>
 
−
 
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And then restart libvirtd and dnsmasq:
 
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<syntaxhighlight>
 
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  service libvirtd restart
 
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  service dnsmasq restart
 
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</syntaxhighlight>
 
−
 
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====== Important Config Files ======
 
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Important Configuration And Log Files (Directories) Location
 
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The following files are required to manage and debug KVM problems:
 
−
 
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  1. /etc/libvirt/ - Main configuration directory.
 
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  2. /etc/libvirt/qemu/ - Virtual machine configuration directory. All xml files regarding VMs are stored here. You can edit them manually or via virt-manager.
 
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  3. /etc/libvirt/qemu/networks/ - Networking for your KVM including default NAT. NAT is only recommended for small setup or desktops. I strongly suggest you use bridged based networking for performance.
 
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  4. /etc/libvirt/qemu/networks/default.xml - The default NAT configuration used by NAT device virbr0.
 
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  5. /var/log/libvirt/ - The default log file directory. All VM specific logs files are stored here.
 
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  6. /etc/libvirt/libvirtd.conf - Master libvirtd configuration file.
 
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  7. /etc/libvirt/qemu.conf - Master configuration file for the QEMU driver.
 
−
 
−
====== Editing the VM XML ======
 
−
libvirt stores it's configuration as xml in '/etc/libvirt/qemu'. The xml is easy to understand, and is similar to VMware *.vmx files. While it is possible to edit these files in place and restart libvirt-bin for the changes to take affect, the recommended method for modifying the attributes of a virtual machine is via virsh (or virt-manager, if it supports changing the hardware you want to change). The concept is simple:
 
−
 
−
  1. export (aka 'dump') the xml of the virtual machine you want to edit
 
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  2. edit the xml
 
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  3. import (aka 'define') the xml
 
−
 
−
For example, to edit the machine named 'foo' (you can get a list of your machines with 'virsh list --all'), do:
 
−
 
−
<syntaxhighlight>
 
−
  $ virsh dumpxml foo > /tmp/foo.xml
 
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  (edit /tmp/foo.xml as needed)
 
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  $ virsh define /tmp/foo.xml
 
 
</syntaxhighlight>
 
</syntaxhighlight>

Revision as of 13:38, 7 November 2012

Check CPU supports KVM

egrep '(vmx|svm)' --color=always /proc/cpuinfo

Install KVM

# on RHEL 5
yum install virt-viewer virt-manager
yum install kvm kvm-qemu-img
OR
yum groupinstall KVM

# on RHEL 6
yum groupinstall  Virtualisation 'Virtualization Client' 'Virtualization Platform' 'Virtualization Tools'

Install the modules

modprobe kvm-intel

Start libvirtd

/etc/init.d/libvirtd restart

Load up virtual manager

virt-manager

Setup Bridged Networking

By Default KVM uses NAT (hosts can see outside world but world cannot see the hosts). To setup bridged networking:

  • Disable NetworkManager
 # chkconfig NetworkManager off
 # chkconfig network on
 # service NetworkManager stop
 # service network start
  • Edit the file: /etc/sysconfig/network-scripts/ifcfg-eth0
 DEVICE="eth0"
 ONBOOT="yes"
 BRIDGE=br0


  • Create the bridge script/file: /etc/sysconfig/network-scripts/ifcfg-br0
 DEVICE=br0
 TYPE=Bridge
 IPADDR=172.28.10.58
 NETMASK=255.255.0.0
 NETWORK=172.28.0.0
 DNS1=172.28.1.3
 ONBOOT=yes
 DELAY=0
  • Configure iptables to allow traffic be forwarded across the bridge
 # iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT
 # service iptables save
 # service iptables restart
  • Reload libvirtd
 # service libvirtd reload
  • Verify it's working fine:
 # brctl show 
 bridge name	bridge id		STP enabled	interfaces
 br0		8000.0025902efb56	no		eth0
                                                       vnet2
 virbr0	8000.525400098976	yes		virbr0-nic
                                                       vnet0

Create the image file

In RHEL6, use virt-install: (dont use any files in /root) 

[root@kvm kvms]$ virt-install \
                 --name=guest1-sl6-64 \
                 --disk path=/vm/guest1-rhel6-64,size=10,sparse=false \
                 --vnc \
                 --vcpus=2 \
                 --ram=2048 \
                 --cdrom=/vm/SL-61-x86_64-2011-07-27-Everything-DVD1.iso \
                 --network bridge=br0 \
                 --os-type=linux \
                 --os-variant=rhel6

Starting install...
Creating storage file guest1-rhel6-64    8% [==-                           ]  17 MB/s | 873 MB     09:13 ETA

Notes from RHEL5 on creating a qcow filesystem (virt-install runs this under the covers) 

dd if=/dev/zero of=/home/viglen/vm_winxp.img bs=1024k count=12000
OR
qemu-img create -f qcow windows.img 12G

Creating files in /root resulted in the following error: 

Starting install...
ERROR    internal error process exited while connecting to monitor: char device redirected to /dev/pts/1
qemu: could not open disk image /root/scratch/SL-61-x86_64-2011-07-27-Everything-DVD1.iso: Permission denied
  • Change CDs using virt-manger -> Open Guest -> Show Virtual Hardware -> CDROM

Start qemu

/usr/libexec/qemu-kvm -hda vig_xp.img  -cdrom vig_xp.iso -m 512 -boot d
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