Posts Tagged ‘ESX’

VMware Hypervisors

Posted: October 12, 2012 in ESX, VM, VMWare
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In IT, a Hypervisor, also called virtual machine manager (VMM), is one of many hardware virtualization techniques allowing multiple operating systems, termed guests, to run concurrently on a host computer. It is so named because it is conceptually one level higher than a supervisory program. The Hypervisor presents to the guest operating systems a virtual operating platform and manages the execution of the guest operating systems. Multiple instances of a variety of operating systems may share the virtualized hardware resources. Hypervisors are very commonly installed on server hardware, with the function of running guest operating systems, that themselves act as servers.

The Core of the vSphere product suite is the Hypervisor.

Hypervisor is the virtualization layer that serves as the foundation for the rest of the product line of VMware.

In the latest version of vSphere (5), the hypervisor comes in the form of VMware ESXi.

Type 1 and Type 2 Hypervisor:

Hypervisors are generally grouped into two classes: type 1 hypervisors and type 2 hypervisors. Type 1 hypervisors run directly on the system hardware and thus are often referred to as bare-metal hypervisors. Type 2 hypervisors require a host operating system, and the host operating system provides I/O device support and memory management.

VMware ESXi is a type 1 bare-metal hypervisor. (In earlier versions of vSphere, VMware ESX was also considered a type 1 bare-metal hypervisor.) Other type 1 bare-metal hypervisors include Microsoft Hyper-V and products based on the open source Xen hypervisor like Citrix XenServer and Oracle VM.


In other words, Type 1 hypervisor runs directly on the hardware; a Type 2 hypervisor runs on operating system.


This is a significant difference from earlier versions of the VMware vSphere product suite. In earlier versions of VMware vSphere, the hypervisor was available in two forms: VMware ESX and VMware ESXi. Although both products shared the same core virtualization engine, supported the same set of virtualization features, leveraged the same licenses, and were both considered baremetal installations, there were still notable architectural differences. In VMware ESX, VMware used a Linux-derived Service Console to provide an interactive environment through which users could interact with the hypervisor. The Linux-based Service Console also included services found in traditional operating systems, such as a firewall, Simple Network Management Protocol (SNMP) agents, and a web server.



–          Not be able to connect to the ESX host through vSphere Client.

–          The vSphere client gives out error message as “Connection Timed Out”

–          You may not be able to Start or Stop the Virtual Machine.

–          The ESX may show as Disconnected from the Central Virtual Server.


Rather than proceeding to restart the ESX host, you can proceed to restart the Management Agents on the ESX host.

(Note: Restarting the Management Tasks may impact any tasks running on that particular ESX)

–          Log into your ESX host using the “Root” Credentials through the SSH Session, you can better use the “Putty” Software to connect to the ESX    host.

–          Feed the IP address of the ESX Host.

–          Then Click on “Open” in the end of Tab.

–          Once get the Console window, Login with Root Credentials

–          Run the below command to restart the Management Agent on the ESX Host:

–          Now you should be able to connect to the ESX host through the vSphere client.


Caution: Ensure Automatic Startup /Shutdown of VM is disabled before running the above command.


  • The Service Console loses connectivity
  • Due to misconfiguration of service console, the network connection fails
  • An additional NIC is added to ESX host


To delete and recreate a virtual switch and Service Console from the command line:


  1. Run the following command to list the name of the vswif adapter:

    esxcfg-vswif -l

  2. Run the following command to delete the vswif adapter:

    esxcfg-vswif –del vswif0

  3. Run the following command to list the name of the vSwitch:

    esxcfg-vswitch -l

  4. Run the following command to delete the vSwitch:

    esxcfg-vswitch -d vSwitch0

  5. Run the following command to create the vSwitch:

    esxcfg-vswitch -a vSwitch0

  6. Run the following commands to create default port groups for vSwitch:

    esxcfg-vswitch -A “VM Network” vSwitch0
    esxcfg-vswitch -A “Service Console” vSwitch0

  7. Run the following command to create the vswif adapter:

    esxcfg-vswif –add –portgroup “Service Console” –ip=nnn.nnn.nnn.nnn –netmask= vswif0

  8. Run the following command to verify that the settings in the network file are correct:

    cat /etc/sysconfig/network


  9. Run the following commands to list all of the network adapters and associate a vmnic which has a link status of up:

    esxcfg-nics -l
    esxcfg-vswitch -L vmnic1 vSwitch0

  10. Run the following command to verify that the vmnic is associated with the vSwitch:

    esxcfg-vswitch -l

  11. Ping an IP address to check for network connectivity. If the ping fails, remove the previous vmnic from the vSwitch and try another adapter that has a link status of up.

    esxcfg-vswitch -U vmnic1 vSwitch0
    esxcfg-vswitch -L vmnic2 vSwitch0

  12. Run the following command to change the vlan ID of a vSwitch:

    [root@server root]# esxcfg-vswitch -p “VM Network 1” -v 10 vSwitch0

  13. If you make any manual changes to /etc/sysconfig/network, run the following command to restart the network service:

    service network restart

  14. Done