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VM Host

  • A VM host is a physical computer running a VMware hypervisor
  • A VCL computer entry must be added for each VM host (Manage Computers > Edit Computer Information)
  • After the computer has been added to VCL, it is designated as a VM host by changing the computer state to vmhostinuse (Manage Computers > Computer Utilities)


  • A VM is a virtual machine managed by VCL
  • A computer entry must be added to VCL for each VM (Manage Computers > Edit Computer Information)
  • Each VM must be assigned to a VM host (Virtual Hosts > VM Hosts tab > Configure Host)
  • VMs do not need to be created manually in VMware, VCL automatically creates and deletes VMs

VM Host Profile

  • A VM host profile contains several parameters which describe how a VM host is configured so that VCL knows how to manage it
  • Each VM host is assigned a VM host profile
  • A VM host profile may be assigned to multiple VM hosts if they are configured identically
  • VM host profiles may be added or modified via Virtual Hosts > VM Host Profiles tab

VMware Products Supported

  • VMware Server 2.x
  • VMware ESX 3.5 - 4.x
  • VMware ESXi 4.x
  • VMware ESXi 5.x

VM Host Management Options

 The VCL management node must be able to control the VM host and the VMs running on it.  VMware provides several different ways of doing this.  VCL currently supports the following methods for remote VM host management:

  • VMware vSphere SDK
  • Use SSH to execute commands directly on the VM (not officially supported by VMware)

The vSphere SDK can only be used if management is not restricted due to the VMware license key installed on the host.  This mainly affects hosts running the free version of ESXi.  Remote management using any of the methods supported by VMware is restricted once a free license key is entered.

If remote management is restricted, the VM host can be managed if SSH is enabled on it.  VCL will execute vim-cmd and other commands on the VM host via SSH. 

How to enable SSH on the VM host:

VMware Server 2.x

Enable the SSH daemon and configure identity key authentication according to the underlying VM host OS

ESX/ESXi 3.5 & 4.0
  • Connect to the console of the ESX/ESXi host
  • Press ALT-F1 - you should see a black screen with the VMware product name at the top
  • Type the word unsupported and press Enter (you won't see the letters appear as you type them)
  • You should see a password prompt, type in the root password and press Enter
  • Edit the file: vi /etc/inetd.conf
  • Uncomment the first line beginning with #ssh by deleting the # character
  • Save the file - press Esc and then :wq
  • Kill the inetd process
    • Determine the PID of the inetd process: ps | grep inetd
      You should see a line that looks like: 5065 5065 busybox inetd
    • Kill the process (enter the PID from the output of the previous command): kill -HUP 5065
ESXi 4.1

Beginning with ESXi 4.1, SSH can be enabled using the vSphere Client:

  • Select the ESXi host
  • Select the Configuration tab
  • Select Security Profile under Software
  • Click Properties
  • Select Remote Tech Support (SSH)
  • Click Options
  • Select Start automatically
  • Click Start
  • Click OK
ESX 5.0

In the case of ESX 5.0:

  • Select the ESXi host
  • Select the Configuration tab
  • Select Security Profile under Software
  • Click Properties
  • Select SSH Server
  • Click Options
  • Confirm that Start automatically is selected
  • Click OK

How to configure ESX/ESXi to use SSH identity key authentication:

SSH identity key authentication must be configured if SSH is used to manage the VM host.

  • Create an SSH key pair on the management node (or use a key you previously created):

    ssh-keygen -t rsa -f /etc/vcl/vcl.key -N '' -b 1024 -C 'VCL root account'

  • Log into the ESX host via SSH (password authentication should work) and create the directory:

    ssh <ESXi host> 'mkdir /.ssh'

  • Copy the public key to the ESXi host:
    ESXi 4.x:

    scp /etc/vcl/ <ESXi host>:/.ssh/authorized_keys

    ESXi 5.x:

    scp /etc/vcl/ <ESXi host>:/etc/ssh/keys-root/authorized_keys

  • Test making an SSH connection using the key:

    ssh -i /etc/vcl/vcl.key <ESXi host>

IMPORTANT: Under ESXi 4.x, the authorized_keys file is erased when the ESXi VM host is rebooted. Complete the following steps to make the authorized_keys file persistent:

Note: VCL will perform these steps automatically when the 1st reservation assigned to the host is processed.

  • Create a compressed tarball file containing the /.ssh directory:

    tar -C / -czf bootbank/vcl.tgz .ssh

  • Edit the /bootbank/boot.cfg file and append ' --- vcl.tgz' to modules line as shown in the following example:

    modules=k.z — s.z — c.z — oem.tgz — license.tgz — m.z — state.tgz — vcl.tgz

    Optionally you can run the following two commands:
    tar -C / -czf vcl.tgz .ssh --add=vcl.tgz --verbose

VM Host Profile Parameters

General Parameters

  • Descriptive name of the VM host profile
Type (deprecated)
  • Will be removed in VCL 2.3
Image (optional)
  • VCL hypervisor image installed on VM host computers using xCAT

    xCAT is not required.  VM host computers may be installed manually or by some other means.

  • If xCAT is not used, select "No Image"
  • VCL has the ability to install a hypervisor image on bare-metal computers using xCAT.  If the image property is configured, the image is installed when a computer's state is changed to vmhostinuse via Manage Computers > Computer Utilities
Username/Password (optional)
  • Name and password of the administrative or root user residing on the VM host
  • This account is used to manage the VM host and VMs assigned to the host
  • The username and password are currently only used if the vSphere SDK is used to manage the VM host and VMs

Storage Parameters

Datastore Path
  • Location where master copies of images are stored which are used by running VMs
  • Example: /vmfs/volumes/nfs-datastore1

    For ESXi, the path configured in the profile may simply be the short datastore name as it appears in the vSphere Client: nfs-datastore1

  • Storage location should be large enough to store all of the images which may be loaded on the VM host (from 100's of GB to several TB)
  • VCL creates a directory for each image in the datastore
  • Images are stored in the vmfs thin vmdk format
  • Datastore Path may either reside on local or network storage
  • Multiple VM hosts can share the same datastore if network storage is used
    • A single datastore may be used by all VM hosts if performance is adequate
    • Multiple VMs on different hosts may access the same Datastore Path image at the same time
    • It is recommended that datastores are shared among hosts so that fewer copies of each image have to be stored
    • The underlying storage hardware and network connectivity from the hosts to the storage must be adequate
    • Storage where the datastore is located should be optimized for read performance
  • VCL configures VMs to access images stored in the Datastore Path in read-only mode
    • Changes made to the VM's hard drive are written to delta files located in the VM Path directory dedicated for the VM

VM Path (optional)
  • Defines path on VM host where VM working directories will reside (contains .vmx, delta, .vswp, nvram files)
  • If not configured, the Datastore Path location will be used
  • VCL creates a directory under the VM Path directory for each VM it creates
    • Contains the .vmx file which defines the VM
    • Contains delta vmdk files which are written to as changes are made to the VM's hard drive
  • VM Path may either reside on local or network storage
  • Location should be dedicated for each VM host
    • Multiple VM hosts should not share the same VM Path location for performance and image safety reasons
    • VM Paths of multiple hosts may reside on the same volume but a subdirectory should be created for each host
  • Storage where the VM Path is located should be optimized for read-write performance

Repository Path (optional)
  • Path where master copies of images are stored which are used to transfer images to VM host datastores or to other repositories:
    • If a reservation is assigned to a host but the image does not exist in that host's datastore, it is copied from the repository to the datastore path when the VM is loaded
    • If the VCL environment contains multiple management nodes and the image does not exist in the repository or the host's datastore, the image will be retrieved from another management node's repository by copying it via SCP
  • The Repository Path parameter does not need to be configured if the VCL environment contains a single management node and all VM hosts share the same Datastore Path
  • Example: /vmfs/volumes/nfs-repository1
  • VMs do not run directly off of the images stored in the repository
  • Setting the Repository Path parameter determines whether or not an additional copy of an image is created when an image is captured
    • If repository path is not configured then only a single copy of the image will exist in the datastore after an image is captured
    • If repository path is configured then two copies of the image will exist after an image is captured - one in the datastore and one in the repository
  • Repository Path location can refer to and be mounted on either the management node or VM host
    • It is highly recommended that the repository be mounted on the VM host
      • When mounted on the VM host, vmdk operations can be done directly on the VM host in a single step
  • Images in the repository are stored in the 2 GB sparse vmdk format
    • The size of the vmdk files will approximately be equal to the amount of actual data saved in the image regardless of the size of the VM's hard drive
    • Storing images in the 2 GB sparse format is necessary to allow images to be transferred via SCP without having to transfer data equal to the entire size of the VM's hard drive
VM Disk
  • Defines whether the storage where the VM host's Datastore Path resides is dedicated to a single host or shared among multiple hosts:
    • localdisk
      • The VM host's Datastore Path is located on local disks or dedicated network storage
      • The VM host is the only host which accesses the Datastore Path
      • Repository Path must be configured
    • networkdisk
      • The VM host's Datastore Path is located on network storage which is shared by other VM hosts
      • Repository Path is optional

The VM Disk parameter does not determine whether or not:
...images are copied from the datastore to the repository during image capture
...images are copied from the repository to the datastore during image load
These are determined by whether or not Repository Path is configured in the profile

Networking Parameters

Virtual Switch
  • Virtual Switch 0 - private VCL management network
  • Virtual Switch 1 - public network used by user making reservation to access the VMs
  • The Virtual Switch parameters should match the network names configured on the VM host
    • For ESXi, the Virtual Switch parameters must match the Virtual Machine Port Group Network Labels configured in the vSphere Client, example:
      • Virtual Switch 0: Public
      • Virtual Switch 1: Private
  • For VMware Server 2.x, the Virtual Switch parameters must match the Network Names configured by running
Generate eth0/eth1 MAC
  • Not used at the current time
  • Will eventually determine whether VMs are assigned MAC addresses defined in the VCL database or if random MAC addresses should be assigned

Configuration Examples

Local Disk Only - Repository Mounted via NFS

The diagram above shows a simple VCL configuration with 1 management node and 2 VMware ESXi hosts.  Network storage is not used.
The local disks on the VM hosts are used to store all of the files used by running VMs including the VM's working directory and the master vmdk image.

A directory on the local disk on the management node is used to as the image repository.  This directory is exported via NFS.  VM hosts mount this directory as a datastore named "repository".  Mounting the repository directly on the VM hosts allows the vmkfstools utility to be used on the VM hosts to copy and convert images directly from the repository to the local datastore in a single step.

If an image is to be loaded on a VM host and that image does not already exist in the VM host's local datastore, it is automatically copied from the repository to the VM host's local datastore at the beginning of the load process.

During image capture, images are automatically copied to from the VM host's local datastore to the repository.  This allows images captured on a VM host to be loaded on any other VM host.

The VM host profile VM Disk parameter is set to localdisk.  This indicates to the load process that the VM host's datastore path is dedicated to the VM host and not shared by other VM hosts.  This allows images to be deleted from the VM host's local datastore if another image must be copied from the repository and not enough space is available.

Local Disk Only - Repository Not Available via NFS

This example is identical to the one above except that the repository located on the management node's local disk is not exported via NFS.  Because of this, image must be transferred using SCP instead of vmkfstools.  This is less desirable than mounting the repository directly on the VM hosts because images cannot be copied and converted in a single step.  Images are stored in the repository in the 2GB sparse format.  This allows the images to be copied via SCP while only transferring the data stored in the image, not the entire size of the hard drive stored in the image.  VMware ESXi cannot run VMs using vmdk images stored in the 2GB sparse format.  Images are converted to the vmfs thin format so that they can be loaded on VMware ESXi.  This adds extra time to the load process if an image does not exist in the VM's local datastore and must be copied from the repository.  It also requires additional space in the VM host's local datastore becuase 2 copies of the image exist while it is being converted.
Note that the VM host profile Repository Path parameter is set to the path on the management node's hard drive.  The code first checks if the path exists on the VM host.  If not, it assumes the repository is not mounted directly on the VM host and the Repository Path value refers to a location on the management node.

Network Storage Only - No Repository

This is an example of a simple configuration where the network storage is used.

A repository is not used in this configuration.  This implies that all VM hosts which will ever be added to this VCL environment will need to be able to connect to the network storage.

A datastore named "datastore" is mounted on every VM host.  Each of these mounts points to the same location on the network storage.  The datastore will contain the master vmdk images.  VMs loaded on the VM hosts will read from these master vmdk images.

A datastore named "vmpath" is also mounted on each VM host.  However, the location each VM host points should be different.  In the example above, vmhost-a-01 points to th the /vmpath01 directory on the network storage and vmhost-a-02 points to the /vmpath02 directory.  These locations may be different network storage filesystems or may be different directories on the same network filesystem.  Even though the mounts on the VM hosts point to different locations, the datastore names configured under ESXi are identical.  This allows you to use the same VCL VM host profile for all of the VM hosts.

The VM host profile VM Disk parameter is set to networkdisk.  This indicates to the load process that the VM host's datastore path is shared by other VM hosts.

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