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Ganeti installation tutorial for RHEL/CentOS/others

This documentation is the short version for RHEL/CentOS/others 7.x and 8.x.

Official full version:

Upgrade / update to the latest version:

Installing the base system

Ganeti works on a single node, but we recommend a configuration with 3 or more nodes. With two nodes, there is a problem with voting to determine the master during a master failover.

Mandatory on all nodes.

Note that Ganeti requires the hostnames of the systems.

e.g. DNS or /etc/hosts:       localhost
# cluster name     gcluster
# node names node1 node2 node3
# instance names instance1 instance2

Installing The Hypervisor

Ganeti supports Xen, KVM, and LXC. The KVM hypervisor is the most commonly used on RHEL/CentOS/Scientific CentOS.

Mandatory on all nodes.

  • KVM on RHEL/CentOS/others 7.x

The oldest version of qemu supported by Ganeti is qemu-2.11. Therefore, it is recommended to install qemu-kvm-ev(version 2.12.x) instead of qemu-kvm(version 1.5.x) on el7.

# centos-release-qemu-ev - QEMU Enterprise Virtualization packages from the CentOS Virtualization SIG repository
yum install centos-release-qemu-ev
yum install qemu-kvm-ev libvirt python-virtinst virt-install
  • KVM on RHEL/CentOS/others 8.x
dnf install qemu-kvm libvirt virt-install

KVM settings

  • KVM on RHEL/CentOS/others

Mandatory on all nodes.

(Optional) Service configuration for libvirt.

Enable services:

systemctl enable libvirtd.service
systemctl enable ksm.service
systemctl enable ksmtuned.service

Disable unused virbrX:

systemctl start libvirtd.service

virsh net-autostart default --disable
virsh net-destroy default

Create bridge interface:

br0 is an example of bridge interface.

  • Using NetworkManager
    • physical interface: eno1
    • bridge interface: br0
    • ipv4.addresses:
    • ipv4.gateway
    • ipv4.dns ","
nmcli connection add type bridge autoconnect yes ipv4.method disabled ipv6.method ignore bridge.stp no bridge.forward-delay 0 con-name br0 ifname br0
nmcli connection modify eno1 connection.slave-type bridge connection.master br0
nmcli connection modify br0 ipv4.method manual ipv4.addresses ""
nmcli connection modify br0 ipv4.gateway "" ipv4.dns ","
nmcli connection up br0; nmcli connection down eno1; nmcli connection up bridge-slave-eno1 &

# VLAN filter support on bridge(VLAN aware bridge)
# Require ganeti-2.16.2-1 RPM or later
# set VLAN 100: gnt-instance modify --net 0:modify,vlan=100 instance1
nmcli connection modify br0 bridge.vlan-filtering yes
nmcli connection down br0; nmcli connection up br0 &

You can setup it easily by using nmcli-cli.

nmcli-cli-bridge-add -x br1 eno1
nmcli-cli-ipv4 -x br1 static ",""
nmcli connection modify br0 bridge.vlan-filtering yes

nmcli connection up br0
nmcli connection down eno1
nmcli connection up bridge-slave-eno1

Allow to bridge interface access.

  • Using iptables

Edit /etc/sysconfig/iptables:

-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -m physdev --physdev-is-bridged -j ACCEPT

Edit /etc/sysconfig/ip6tables:

-A INPUT -j REJECT --reject-with icmp6-adm-prohibited
-A FORWARD -m physdev --physdev-is-bridged -j ACCEPT

Apply firewall rules:

iptables-restore < /etc/sysconfig/iptables
ip6tables-restore < /etc/sysconfig/ip6tables

Setting up yum/dnf repositories

Mandatory on all nodes.

Install ELRepo repository for DRBD packages:

# RHEL/CentOS/others **7.x**
yum install elrepo-release
yum-config-manager --disable elrepo

# RHEL/CentOS/others **8.x**
dnf install elrepo-release
dnf config-manager --disable elrepo

Install EPEL repository for dependency packages:

# RHEL/CentOS/others **7.x**
yum install epel-release
yum-config-manager --disable epel

# RHEL/CentOS/others **8.x**
dnf install epel-release
dnf config-manager --disable epel

Install Integ Ganeti repository:

# RHEL/CentOS/others **7.x**
yum install
yum-config-manager --disable integ-ganeti

# RHEL/CentOS/others **8.x**
dnf install
dnf config-manager --disable integ-ganeti

Installing DRBD

Mandatory on all nodes.

Install DRBD package:

yum --enablerepo=elrepo install kmod-drbd84 drbd84-utils

Enable drbd.service:

systemctl enable drbd.service

Create /etc/modules-load.d/drbd.conf:

echo "drbd" >> /etc/modules-load.d/drbd.conf

Create /etc/modprobe.d/drbd.conf:

echo "options drbd minor_count=128 usermode_helper=/bin/true" >> /etc/modprobe.d/drbd.conf

Load DRBD kernel module:

systemctl start systemd-modules-load

Configuring LVM

Mandatory on all nodes.

The volume group is required to be at least 20GiB.

If you haven't configured your LVM volume group at install time you need to do it before trying to initialize the Ganeti cluster. This is done by formatting the devices/partitions you want to use for it and then adding them to the relevant volume group.

pvcreate /dev/sda3
vgcreate vmvg /dev/sda3


pvcreate /dev/sdb1
pvcreate /dev/sdc1
vgcreate vmvg /dev/sdb1 /dev/sdc1

If you want to add a device later you can do so with the vgextend command:

pvcreate /dev/sdd1
vgextend vmvg /dev/sdd1

(Optional) it is recommended to configure LVM not to scan the DRBD devices for physical volumes. This can be accomplished by editing /etc/lvm/lvm.conf and adding the /dev/drbd[0-9]+ regular expression to the filter variable, like this:

filter = ["r|/dev/cdrom|", "r|/dev/drbd[0-9]+|" ]

Installing Ganeti

Mandatory on all nodes.

  • Install Ganeti:
yum --enablerepo=epel,integ-ganeti install ganeti
  • (Optional) Install Ganeti Instance Debootstrap:
yum --enablerepo=epel,integ-ganeti install ganeti-instance-debootstrap

Required ports(default):

Several network ports must be available and opened so the different nodes can communicate properly between them.

  • ganeti-noded: 1811/tcp
  • ganeti-confd: 1814/udp
  • ganeti-rapi: 5080/tcp
  • ganeti-mond: 1815/tcp
  • ganeti-metad: 80/tcp
  • DRBD/VNC port for instances: 11000/tcp - 14999/tcp

Service configuration:

systemctl enable
systemctl enable ganeti-confd.service
systemctl enable ganeti-noded.service
systemctl enable ganeti-wconfd.service
systemctl enable ganeti-rapi.service
systemctl enable ganeti-luxid.service
systemctl enable ganeti-kvmd.service

# Optional: ganeti-mond is the daemon providing the Ganeti monitoring functionality.
systemctl enable ganeti-mond.service

# Optional: ganeti-metad is the daemon providing the metadata service.
systemctl enable ganeti-metad.service

Initializing the cluster

Mandatory on one node per cluster.

Create ~/.ssh directory.

if [[ ! -d ~/.ssh ]]; then mkdir ~/.ssh; chmod 600 ~/.ssh; fi

Initialize a cluster.

gnt-cluster init --vg-name <VOLUMEGROUP> --master-netdev <MASTERINTERFACE> --nic-parameters link=<BRIDGEINTERFACE> <CLUSTERNAME>

Example for KVM:

# gnt-cluster init --vg-name vmvg --master-netdev <MASTERINTERFACE> --enabled-hypervisors kvm --nic-parameters link=<BRIDGEINTERFACE> gcluster
gnt-cluster init --vg-name vmvg --master-netdev eno1 --enabled-hypervisors kvm --nic-parameters link=br0 gcluster

Set default metavg parameter for DRBD disk

gnt-cluster modify -D drbd:metavg=vmvg

Enable use_bootloader for using VM's boot loader.

gnt-cluster modify --hypervisor-parameters kvm:kernel_path=

Optional cluster configurations

The settings using the gnt-cluster command are global settings that are reflected in all instances. You can override the setting values for individual instance using the gnt-instance command.

Enable user shutdown: --user-shutdown

The --user-shutdown option enables or disables user shutdown detection at the cluster level. User shutdown detection allows users to initiate instance poweroff from inside the instance, and Ganeti will report the instance status as USER_down (as opposed, to ERROR_down) and the watcher will not restart these instances, thus preserving their instance status.

gnt-cluster modify --user-shutdown yes

Optimizing DRBD performance: -D drbd

This optimizes the DRBD performance.

# For example with 1 Gbps NIC
gnt-cluster modify -D drbd:c-min-rate=10240,c-max-rate=81920,resync-rate=81920
gnt-cluster modify -D drbd:disk-custom='--al-extents 3833',net-custom='--max-buffers 8000 --max-epoch-size 8000'

Change the CPU type: cpu_type

This parameter determines the emulated cpu for the instance.

# For clusters with the same CPU, it is possible to use the 'host' cpu type:
gnt-cluster modify -H kvm:cpu_type=host

# For example on a cluster using IvyBridge-IBRS generation or later CPUs, the following command can be used:
gnt-cluster modify -H kvm:cpu_type='IvyBridge-IBRS\,+pcid\,+ssbd\,+md-clear'

# Show available CPU types:
/usr/libexec/qemu-kvm -cpu help

Change the CPU topology: cpu_sockets

Number of emulated CPU sockets.

gnt-cluster modify -H kvm:cpu_sockets=1

Change the NIC type: nic_type

This parameter determines the way the network cards are presented to the instance.

# Use paravirtual
gnt-cluster modify -H kvm:nic_type=paravirtual

# Use e1000
gnt-cluster modify -H kvm:nic_type=e1000

Change the VGA type: vga

Emulated vga mode, passed the the kvm -vga option.

gnt-cluster modify -H kvm:vga="std"

Change the keymap: keymap

This option specifies the keyboard mapping to be used. It is only needed when using the VNC console.

gnt-cluster modify -H kvm:keymap=ja

Extra option for KVM: kvm_extra

Any other option to the KVM hypervisor.

# For example:
# - Enable KVM: -enable-kvm
# - Add virtio-rng device: -device virtio-rng-pci\,bus=pci.0\,addr=0x1e\,max-bytes=1024\,period=1000
# - Set video memory(MB): -global VGA.vgamem_mb=64
gnt-cluster modify -H kvm:kvm_extra="-enable-kvm -device virtio-rng-pci\,bus=pci.0\,addr=0x1e\,max-bytes=1024\,period=1000 -global VGA.vgamem_mb=64"

Verifying the cluster

Mandatory on master node.

gnt-cluster verify

Joining the nodes to the cluster

Mandatory on master node.

After you have initialized your cluster you need to join the other nodes to it. You can do so by executing the following command on the master node.

gnt-node add <NODENAME>
gnt-node add node2

gnt-node add node3

... and more node.


  • gnt-node add node2 returns with the error:
Node daemon on didn't answer queries within 10.0 seconds

Make sure that you have port 1811 open (ss -anpt | grep 1811)

  • gnt-cluster verify on master returns an error after Verifying node status:
ERROR: node ssh communication with node '': ssh problem: ssh_exchange_identification: read: Connection reset by peer\'r\n

Initiate a manual ssh connection from node2 to node1 and vice versa.

Manage ganeti services

Mandatory on all nodes.


systemctl start
systemctl start ganeti-kvmd.service

# Optional: ganeti-metad is the daemon providing the metadata service.
systemctl start ganeti-metad.service


systemctl stop ganeti-metad.service
systemctl stop ganeti-kvmd.service
systemctl stop

Setting up and managing virtual instances

Mandatory on master node.

Setting up virtual instances

  • Setting up RHEL/CentOS/others

We recommend to use Ganeti Instance Image (yum repository).

  • Setting up Debian (require ganeti-instance-debootstrap)

Installation will be successful, but gnt-instance console doesn't work.

gnt-instance add -t drbd -n node1:node2 -o debootstrap+default --disk 0:size=8G -B vcpus=2,maxmem=1024,minmem=512 instance1

# With no check, no start, and no install
gnt-instance add -t drbd -n node2:node1 -o debootstrap+default --disk 0:size=8G -B vcpus=2,maxmem=1024,minmem=512 --no-ip-check --no-name-check --no-start --no-install

Install custom OS using ISO file

Check the VNC port of the created instance:

# gnt-instance info | grep "console connection"
  console connection: vnc to (display 5101)

Start the instance with ISO image:

gnt-instance start -H cdrom_image_path=/path/to/install.iso,boot_order=cdrom

Connect to using a VNC client and follow the on-screen instructions to complete the installation.