Hosts

In order to use your existing physical nodes, you have to add them to OpenNebula as Hosts. To add a Host only its hostname and type is needed.

Warning

Before adding a Linux Host check that you can SSH to it without being prompted for a password.

Creating and Deleting Hosts

Hosts are the servers managed by OpenNebula responsible for running VMs. To use these Hosts in OpenNebula you need to register them so they are monitored and made available to the scheduler.

Creating a Host:

$ onehost create host01 --im kvm --vm kvm
ID: 0

The parameters are:

--im: Information Manager driver.
--vm: Virtual Machine Manager driver.

Note

In the examples included in this guide we’ll use KVM as the hypervisor. Note that the procedure will be the same for any other hypervisor; only the name will need to be changed.

To remove a Host you can either specify it by ID or by name. The following commands are equivalent:

$ onehost delete host01
$ onehost delete 0

Showing and Listing Hosts

To display information about a single Host, use the show command:

$ onehost show server

HOST 0 INFORMATION
ID                    : 0
NAME                  : server
CLUSTER               : default
STATE                 : MONITORED
IM_MAD                : kvm
VM_MAD                : kvm
LAST MONITORING TIME  : -

HOST SHARES
RUNNING VMS           : 0
MEMORY
  TOTAL               : 31.1G
  TOTAL +/- RESERVED  : 31.1G
  USED (REAL)         : 0K
  USED (ALLOCATED)    : 0K
CPU
  TOTAL               : 800
  TOTAL +/- RESERVED  : 800
  USED (REAL)         :
  USED (ALLOCATED)    : 0

LOCAL SYSTEM DATASTORE #0 CAPACITY
TOTAL:                : 467.7G
USED:                 : 113.5G
FREE:                 : 354.2G

MONITORING INFORMATION
ARCH="x86_64"
CPUSPEED="3350"
HOSTNAME="pc-ruben"
HYPERVISOR="kvm"
IM_MAD="kvm"
KVM_CPU_MODEL="Skylake-Client-noTSX-IBRS"
KVM_CPU_FEATURES="vme,ds,acpi,ss,ht,tm,pbe,dtes64,monitor,ds_cpl,vmx,smx,est,tm2,xtpr,pdcm,pcid,dca,osxsave,arat,md-clear,stibp,ssbd,xsaveopt,pdpe1gb,invtsc"
KVM_CPU_MODELS="486 pentium pentium2 pentium3 pentiumpro coreduo n270 core2duo qemu32 kvm32 cpu64-rhel5 cpu64-rhel6 qemu64 kvm64 Conroe Penryn Nehalem Nehalem-IBRS Westmere Westmere-IBRS SandyBridge SandyBridge-IBRS IvyBridge IvyBridge-IBRS Haswell-noTSX Haswell-noTSX-IBRS Haswell Haswell-IBRS Broadwell-noTSX Broadwell-noTSX-IBRS Broadwell Broadwell-IBRS Skylake-Client Skylake-Client-IBRS Skylake-Client-noTSX-IBRS Skylake-Server Skylake-Server-IBRS Skylake-Server-noTSX-IBRS Cascadelake-Server Cascadelake-Server-noTSX Icelake-Client Icelake-Client-noTSX Icelake-Server Icelake-Server-noTSX Cooperlake Snowridge athlon phenom Opteron_G1 Opteron_G2 Opteron_G3 Opteron_G4 Opteron_G5 EPYC EPYC-IBPB EPYC-Rome Dhyana"
KVM_MACHINES="pc-i440fx-5.2 pc pc-q35-5.2 q35 pc-i440fx-2.12 pc-i440fx-2.0 pc-q35-4.2 pc-i440fx-2.5 pc-i440fx-4.2 pc-i440fx-1.5 pc-q35-2.7 pc-i440fx-2.2 pc-1.1 pc-i440fx-2.7 pc-q35-2.4 pc-q35-2.10 pc-i440fx-1.7 pc-q35-5.1 pc-q35-2.9 pc-i440fx-2.11 pc-q35-3.1 pc-q35-4.1 pc-i440fx-2.4 pc-1.3 pc-i440fx-4.1 pc-i440fx-5.1 pc-i440fx-2.9 isapc pc-i440fx-1.4 pc-q35-2.6 pc-i440fx-3.1 pc-q35-2.12 pc-i440fx-2.1 pc-1.0 pc-i440fx-2.6 pc-q35-4.0.1 pc-i440fx-1.6 pc-q35-5.0 pc-q35-2.8 pc-i440fx-2.10 pc-q35-3.0 pc-q35-4.0 microvm pc-i440fx-2.3 pc-1.2 pc-i440fx-4.0 pc-i440fx-5.0 pc-i440fx-2.8 pc-q35-2.5 pc-i440fx-3.0 pc-q35-2.11"
MODELNAME="Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz"
RESERVED_CPU=""
RESERVED_MEM=""
VERSION="7.0.0"
VM_MAD="kvm"

NUMA NODES

  ID CORES        USED FREE
   0 -- -- -- --  0    8

NUMA MEMORY

 NODE_ID TOTAL    USED_REAL            USED_ALLOCATED       FREE
       0 31.1G    0K                   0K                   0K

NUMA HUGEPAGES

 NODE_ID SIZE     TOTAL    FREE     USED
       0 2M       0        0        0
       0 1024M    0        0        0

WILD VIRTUAL MACHINES

NAME                                                      DEPLOY_ID  CPU     MEMORY

VIRTUAL MACHINES

ID USER     GROUP    NAME            STAT UCPU    UMEM HOST             TIME
13 oneadmin oneadmin kvm1-13         runn  0.0   1024M server       8d 06h14

The information of a Host contains:

General information of the Host including its name and the drivers used to interact with it.
Capacity (Host Shares) for CPU and memory.
Local datastore information (Local System Datastore) if the Host is configured to use a local datastore (e.g., in Local transfer mode).
Monitoring Information, including PCI devices and NUMA information of the node. You can also find hypervisor specific information here.
Virtual Machines allocated to the Host. Wild are Virtual Machines running on the Host but not started by OpenNebula.

To see a list of all the Hosts:

$ onehost list
  ID NAME            CLUSTER   RVM      ALLOCATED_CPU      ALLOCATED_MEM STAT
   0 server          server      1    100 / 400 (25%) 1024M / 7.3G (13%) on
   1 kvm1            kvm         0                  -                  - off
   2 kvm2            kvm         0                  -                  - off

The above information can be also displayed in XML, JSON, or CSV format using -x or -j or -c, respectively.

Host States

In order to manage the life cycle of a Host it can be set to different operation modes: enabled (on), disabled (dsbl), and offline (off). The different operation status for each mode is described in the following table:

OP. MODE	MONITORING	VM DEPLOYMENT		MEANING
OP. MODE	MONITORING	MANUAL	SCHED	MEANING
ENABLED (on)	Yes	Yes	Yes	The Host is fully operational
UPDATE (update)	Yes	Yes	Yes	The Host is being monitored
DISABLED (dsbl)	Yes	Yes	No	Disabled, e.g. to perform maintenance operations
OFFLINE (off)	No	No	No	The Host is totally offline
ERROR (err)	Yes	Yes	No	Error while monitoring the Host, use `onehost show` for the error description.
RETRY (retry)	Yes	Yes	No	Monitoring a Host in error state

Host Operations

The onehost tool provides commands to set the operation mode of a Host: disable, offline, and enable, for example:

$ onehost disable 0

To re-enable the Host, use the enable command:

$ onehost enable 0

Similarly, to take the Host offline:

$ onehost offline 0

Note

onehost disable and onehost offline do not change the state of VMs already running on the Host. If you need to automatically migrate running VMs use onehost flush.

Apart from the commands above, the onehost tool also provides some commands that allow you to easily perform common operations on a Host.

You can use forceupdate subcommand to reset the monitoring process on the Host:

$ onehost forceupdate 0

The flush command will migrate all the active VMs in the specified Host to another server with enough capacity. At the same time, the specified Host will be disabled so no more Virtual Machines are deployed in it. This command is useful to clean a Host of active VMs. The migration process can be done by a resched action or by a recover delete-recreate action; it can be configured in /etc/one/cli/onehost.yaml by setting the field default_actions\flush to delete-recreate or to resched. Here is an example:

:default_actions:
  - :flush: delete-recreate

Custom Host Attributes

You can add custom attributes either by creating a probe in the host or by updating the Host information with: onehost update.

For example, to label a Host as production we can add a custom tag TYPE:

$ onehost update
...
TYPE="production"

This tag can be used at a later time for scheduling purposes, see more details here.

Updating Host Files

When OpenNebula monitors a Host it copies driver files to /var/tmp/one. When these files are updated they need to be copied again to the Hosts with the sync command. To keep track of the probes version there’s a file in /var/lib/one/remotes/VERSION. By default this holds the OpenNebula version (e.g., ‘7.0.0’). This version can be seen in the Hosts by using onehost show <host>:

$ onehost show 0
HOST 0 INFORMATION
ID                    : 0
[...]
MONITORING INFORMATION
VERSION="7.0.0"
[...]

The command onehost sync only updates the Hosts with VERSION lower than the one in the file /var/lib/one/remotes/VERSION. In case you modify the probes this VERSION file should be modified with a greater value, for example “7.0.0.1”.

In case you want to force an upgrade, that is, without any VERSION checking, you can do it by using the --force option:

$ onehost sync --force

You can also select which Hosts you want to upgrade by naming them or selecting a cluster:

$ onehost sync host01,host02,host03
$ onehost sync -c myCluster

Wild VMs

The monitoring mechanism in OpenNebula reports all VMs found in a hypervisor, even those not launched through OpenNebula. These VMs are referred to as Wild VMs. The Wild VMs can be spotted through the onehost show command:

$ onehost show 3
HOST 3 INFORMATION
ID                    : 3
NAME                  : MyAWSHost
CLUSTER               : -
STATE                 : MONITORED
[...]
WILD VIRTUAL MACHINES
                    NAME                            DEPLOY_ID  CPU     MEMORY
           Ubuntu14.04VM 4223f951-243a-b31a-018f-390a02ff5c96    1       2048
                 CentOS7 422375e7-7fc7-4ed1-e0f0-fb778fe6e6e0    1       2048

Warning

Wild VMs’ support and limitations may differ depending on the virtualization driver used (e.g., KVM or LXC). In order to find more specific information for the virtualization driver you’re using, please check the corresponding driver guide.

Using Sunstone to Manage Hosts

You can also manage your Hosts using Sunstone UI Interface. Select the Host tab and there you will be able to create, enable, disable, delete, and see information about your Hosts in a user-friendly way.

Create new hosts

We value your feedback

Was this information helpful?

Glad to hear it

Sorry to hear that