Hosts and resource pools

This section describes how resource pools can be created through a series of examples using the xe command line interface (CLI). A simple NFS-based shared storage configuration is presented and several simple VM management examples are discussed. It also contains procedures for dealing with physical node failures.

Citrix Hypervisor servers and resource pools overview

A resource pool comprises multiple Citrix Hypervisor server installations, bound together to a single managed entity which can host Virtual Machines. If combined with shared storage, a resource pool enables VMs to be started on any Citrix Hypervisor server which has sufficient memory. The VMs can then be dynamically moved among Citrix Hypervisor servers while running with a minimal downtime (live migration). If an individual Citrix Hypervisor server suffers a hardware failure, the administrator can restart failed VMs on another Citrix Hypervisor server in the same resource pool. When high availability is enabled on the resource pool, VMs automatically move to another host when their host fails. Up to 64 hosts are supported per resource pool, although this restriction is not enforced.

A pool always has at least one physical node, known as the master. Only the master node exposes an administration interface (used by XenCenter and the Citrix Hypervisor Command Line Interface, known as the xe CLI). The master forwards commands to individual members as necessary.

Note:

When the pool master fails, master re-election takes place only if high availability is enabled.

Requirements for creating resource pools

A resource pool is a homogeneous (or heterogeneous with restrictions) aggregate of one or more Citrix Hypervisor servers, up to a maximum of 64. The definition of homogeneous is:

• CPUs on the server joining the pool are the same (in terms of the vendor, model, and features) as the CPUs on servers already in the pool.

• The server joining the pool is running the same version of Citrix Hypervisor software, at the same patch level, as the servers already in the pool.

The software enforces extra constraints when joining a server to a pool. In particular, Citrix Hypervisor checks that the following conditions are true for the server joining the pool:

• The server is not a member of an existing resource pool.

• The server has no shared storage configured.

• The server is not hosting any running or suspended VMs.

• No active operations are in progress on the VMs on the server, such as a VM shutting down.

• The clock on the server is synchronized to the same time as the pool master (for example, by using NTP).

• The management interface of the server is not bonded. You can configure the management interface when the server successfully joins the pool.

• The management IP address is static, either configured on the server itself or by using an appropriate configuration on your DHCP server.

Citrix Hypervisor servers in resource pools can contain different numbers of physical network interfaces and have local storage repositories of varying size. In practice, it is often difficult to obtain multiple servers with the exact same CPUs, and so minor variations are permitted. If it is acceptable to have hosts with varying CPUs as part of the same pool, you can force the pool-joining operation by passing the --force parameter.

All hosts in the pool must be in the same site and connected by a low latency network.

Note:

Servers providing shared NFS or iSCSI storage for the pool must have a static IP address.

A pool must contain shared storage repositories to select on which Citrix Hypervisor server to run a VM and to move a VM between Citrix Hypervisor servers dynamically. If possible create a pool after shared storage is available. We recommend that you move existing VMs with disks located in local storage to shared storage after adding shared storage. You can use the xe vm-copy command or use XenCenter to move VMs.

Create a resource pool

Resource pools can be created using XenCenter or the CLI. When a new host joins a resource pool, the joining host synchronizes its local database with the pool-wide one, and inherits some settings from the pool:

• VM, local, and remote storage configuration is added to the pool-wide database. This configuration is applied to the joining host in the pool unless you explicitly make the resources shared after the host joins the pool.

• The joining host inherits existing shared storage repositories in the pool. Appropriate PBD records are created so that the new host can access existing shared storage automatically.

• Networking information is partially inherited to the joining host: the structural details of NICs, VLANs, and bonded interfaces are all inherited, but policy information is not. This policy information, which must be reconfigured, includes:

  • The IP addresses of the management NICs, which are preserved from the original configuration.

  • The location of the management interface, which remains the same as the original configuration. For example, if the other pool hosts have management interfaces on a bonded interface, the joining host must be migrated to the bond after joining.

  • Dedicated storage NICs, which must be reassigned to the joining host from XenCenter or the CLI, and the PBDs replugged to route the traffic accordingly. This is because IP addresses are not assigned as part of the pool join operation, and the storage NIC works only when this is correctly configured. For more information on how to dedicate a storage NIC from the CLI, see Manage networking.

Note:

You can only join a new host to a resource pool when the host’s management interface is on the same tagged VLAN as that of the resource pool.

Add a host to a pool by using the xe CLI

1. Open a console on the Citrix Hypervisor host that you want to join to a pool.

2. Join the Citrix Hypervisor host to the pool by issuing the command:

   xe pool-join master-address=<address of pool master> master-username=<administrator username> master-password=<password>
   <!--NeedCopy-->
   

   The master-address must be set to the fully qualified domain name of the pool master. The password must be the administrator password set when the pool master was installed.

Note:

When you join a host to a pool, the administrator password for the joining host is automatically changed to match the administrator password of the pool master.

Citrix Hypervisor servers belong to an unnamed pool by default. To create your first resource pool, rename the existing nameless pool. Use tab-complete to find the pool_uuid:

xe pool-param-set name-label="New Pool" uuid=pool_uuid
<!--NeedCopy-->

Create heterogeneous resource pools

Citrix Hypervisor simplifies expanding deployments over time by allowing disparate host hardware to be joined in to a resource pool, known as heterogeneous resource pools. Heterogeneous resource pools are made possible by using technologies in Intel (FlexMigration) and AMD (Extended Migration) CPUs that provide CPU “masking” or “leveling”. The CPU masking and leveling features allow a CPU to be configured to appear as providing a different make, model, or functionality than it actually does. This feature enables you to create pools of hosts with disparate CPUs but still safely support live migration.

Note:

The CPUs of Citrix Hypervisor servers joining heterogeneous pools must be of the same vendor (that is, AMD, Intel) as the CPUs of the hosts already in the pool. However, the servers are not required to be the same type at the level of family, model, or stepping numbers.

Citrix Hypervisor simplifies the support of heterogeneous pools. Hosts can now be added to existing resource pools, irrespective of the underlying CPU type (as long as the CPU is from the same vendor family). The pool feature set is dynamically calculated every time:

• A new host joins the pool

• A pool member leaves the pool

• A pool member reconnects following a reboot

Any change in the pool feature set does not affect VMs that are currently running in the pool. A Running VM continues to use the feature set which was applied when it was started. This feature set is fixed at boot and persists across migrate, suspend, and resume operations. If the pool level drops when a less-capable host joins the pool, a running VM can be migrated to any host in the pool, except the newly added host. When you move or migrate a VM to a different host within or across pools, Citrix Hypervisor compares the VM’s feature set against the feature set of the destination host. If the feature sets are found to be compatible, the VM is allowed to migrate. This enables the VM to move freely within and across pools, regardless of the CPU features the VM is using. If you use Workload Balancing to select an optimal destination host to migrate your VM, a host with an incompatible feature set will not be recommended as the destination host.

Add shared storage

For a complete list of supported shared storage types, see Storage repository formats. This section shows how shared storage (represented as a storage repository) can be created on an existing NFS server.

To add NFS shared storage to a resource pool by using the CLI

1. Open a console on any Citrix Hypervisor server in the pool.

2. Create the storage repository on server:/path by issuing the following command:

   xe sr-create content-type=user type=nfs name-label="Example SR" shared=true \
       device-config:server=server \
       device-config:serverpath=path
   <!--NeedCopy-->
   

   device-config:server Is the host name of the NFS server and device-config:serverpath is the path on the NFS server. As shared is set to true, shared storage is automatically connected to every Citrix Hypervisor server in the pool. Any Citrix Hypervisor servers that join later are also connected to the storage. The Universally Unique Identifier (UUID) of the storage repository is printed on the screen.

3. Find the UUID of the pool by running the following command:

   xe pool-list
   <!--NeedCopy-->
   

4. Set the shared storage as the pool-wide default with the following command:

   xe pool-param-set uuid=pool_uuid default-SR=sr_uuid
   <!--NeedCopy-->
   

   As the shared storage has been set as the pool-wide default, all future VMs have their disks created on shared storage by default. For information about creating other types of shared storage, see Storage repository formats.

Remove Citrix Hypervisor servers from a resource pool

Note:

Before removing any Citrix Hypervisor server from a pool, ensure that you shut down all the VMs running on that host. Otherwise, you can see a warning stating that the host cannot be removed.

When you remove (eject) a host from a pool, the machine is rebooted, reinitialized, and left in a state similar to a fresh installation. Do not eject Citrix Hypervisor servers from a pool if there is important data on the local disks.

To remove a host from a resource pool by using the CLI

1. Open a console on any host in the pool.

2. Find the UUID of the host by running the following command:

   xe host-list
   <!--NeedCopy-->
   

3. Eject the required host from the pool:

   xe pool-eject host-uuid=host_uuid
   <!--NeedCopy-->
   

   The Citrix Hypervisor server is ejected and left in a freshly installed state.

   Warning:

   Do not eject a host from a resource pool if it contains important data stored on its local disks. All of the data is erased when a host is ejected from the pool. If you want to preserve this data, copy the VM to shared storage on the pool using XenCenter, or the xe vm-copy CLI command.

When Citrix Hypervisor servers containing locally stored VMs are ejected from a pool, the VMs will be present in the pool database. The locally stored VMs are also visible to the other Citrix Hypervisor servers. The VMs do not start until the virtual disks associated with them have been changed to point at shared storage seen by other Citrix Hypervisor servers in the pool, or removed. Therefore, we recommend that you move any local storage to shared storage when joining a pool. Moving to shared storage allows individual Citrix Hypervisor servers to be ejected (or physically fail) without loss of data.

Note:

When a host is removed from a pool that has its management interface on a tagged VLAN network, the machine is rebooted and its management interface will be available on the same network.

Prepare a pool of Citrix Hypervisor servers for maintenance

Before performing maintenance operations on a host that is part of a resource pool, you must disable it. Disabling the host prevents any VMs from being started on it. You must then migrate its VMs to another Citrix Hypervisor server in the pool. You can do this by placing the Citrix Hypervisor server in to Maintenance mode using XenCenter. For more information, see Run in maintenance mode in the XenCenter documentation.

Backup synchronization occurs every 24 hrs. Placing the master host in to maintenance mode results in the loss of the last 24 hrs of RRD updates for offline VMs.

Warning:

We highly recommend rebooting all Citrix Hypervisor servers before installing an update and then verifying their configuration. Some configuration changes only take effect when the Citrix Hypervisor server is rebooted, so the reboot may uncover configuration problems that can cause the update to fail.

To prepare a host in a pool for maintenance operations by using the CLI

1. Run the following command:

   xe host-disable uuid=Citrix Hypervisor_host_uuid
   xe host-evacuate uuid=Citrix Hypervisor_host_uuid
   <!--NeedCopy-->
   

   This command disables the Citrix Hypervisor server and then migrates any running VMs to other Citrix Hypervisor servers in the pool.

2. Perform the desired maintenance operation.

3. Enable the Citrix Hypervisor server when the maintenance operation is complete:

   xe host-enable
   <!--NeedCopy-->
   

4. Restart any halted VMs and resume any suspended VMs.

Export resource pool data

The Export Resource Data option allows you to generate a resource data report for your pool and export the report into an .xls or .csv file. This report provides detailed information about various resources in the pool such as, servers, networks, storage, virtual machines, VDIs, and GPUs. This feature enables administrators to track, plan, and assign resources based on various workloads such as CPU, storage, and Network.

Note:

Export Resource Pool Data is available for Citrix Hypervisor Premium Edition customers, or those who have access to Citrix Hypervisor through their Citrix Virtual Apps and Desktops entitlement or Citrix DaaS entitlement.

The list of resources and various types of resource data that are included in the report:

Server:

• Name
• Pool Master
• UUID
• Address
• CPU Usage
• Network (avg/max KBs)
• Used Memory
• Storage
• Uptime
• Description

Networks:

• Name
• Link Status
• MAC
• MTU
• VLAN
• Type
• Location

VDI:

• Name
• Type
• UUID
• Size
• Storage
• Description

Storage:

• Name
• Type
• UUID
• Size
• Location
• Description

VMs:

• Name
• Power State
• Running on
• Address
• MAC
• NIC
• Operating System
• Storage
• Used Memory
• CPU Usage
• UUID
• Uptime
• Template
• Description

GPU:

• Name
• Servers
• PCI Bus Path
• UUID
• Power Usage
• Temperature
• Used Memory
• Computer Utilization

Note:

Information about GPUs is available only if there are GPUs attached to your Citrix Hypervisor server.

To export resource data

1. In the XenCenter Navigation pane, select Infrastructure and then select the pool.

2. Select the Pool menu and then Export Resource Data.

3. Browse to a location where you would like to save the report and then click Save.

Host power-on

Powering on hosts remotely

You can use the Citrix Hypervisor server Power On feature to turn a server on and off remotely, either from XenCenter or by using the CLI.

To enable host power, the host must have one of the following power-control solutions:

• Wake on LAN enabled network card.

• Dell Remote Access Cards (DRAC). To use Citrix Hypervisor with DRAC, you must install the Dell supplemental pack to get DRAC support. DRAC support requires installing the RACADM command-line utility on the server with the remote access controller and enabling DRAC and its interface. RACADM is often included in the DRAC management software. For more information, see Dell’s DRAC documentation.

• A custom script based on the management API that enables you to turn the power on and off through Citrix Hypervisor. For more information, see Configuring a custom script for the Host Power On feature in the following section.

Using the Host Power On feature requires two tasks:

1. Ensure the hosts in the pool support controlling the power remotely. For example, they have Wake on LAN functionality or a DRAC card, or you have created a custom script).

2. Enable the Host Power On functionality using the CLI or XenCenter.

Use the CLI to manage host power-on

You can manage the Host Power On feature using either the CLI or XenCenter. This section provides information about managing it with the CLI.

Host Power On is enabled at the host level (that is, on each Citrix Hypervisor).

After you enable Host Power On, you can turn on hosts using either the CLI or XenCenter.

To enable host power-on by using the CLI

Run the command:

xe host-set-power-on-mode host=<host uuid> \
    power-on-mode=("" , "wake-on-lan", "DRAC","custom") \
    power-on-config=key:value
<!--NeedCopy-->

For DRAC the keys are power_on_ip to specify the password if you are using the secret feature. For more information, see Secrets.

To turn on hosts remotely by using the CLI

Run the command:

xe host-power-on host=<host uuid>
<!--NeedCopy-->

Configure a custom script for the Host Power On feature

If your server’s remote-power solution uses a protocol that is not supported by default (such as Wake-On-Ring or Intel Active Management Technology), you can create a custom Linux Python script to turn on your Citrix Hypervisor computers remotely. However, you can also create custom scripts for DRAC and Wake on LAN remote-power solutions.

This section provides information about configuring a custom script for Host Power On using the key/value pairs associated with the Citrix Hypervisor API call host.power_on.

When you create a custom script, run it from the command line each time you want to control power remotely on a Citrix Hypervisor server. Alternatively, you can specify it in XenCenter and use the XenCenter UI features to interact with it.

The Citrix Hypervisor API is documented in the document, the Citrix Hypervisor Management API, which is available from the developer documentation website.

Warning:

Do not change the scripts provided by default in the /etc/xapi.d/plugins/ directory. You can include new scripts in this directory, but you must never change the scripts contained in that directory after installation.

Key/Value Pairs

To use Host Power On, configure the host.power_on_mode and host.power_on_config keys. See the following section for information about the values.

There is also an API call that lets you set these fields simultaneously:

void host.set_host_power_on_mode(string mode, Dictionary<string,string> config)
<!--NeedCopy-->

host.power_on_mode

• Definition: Contains key/value pairs to specify the type of remote-power solution (for example, Dell DRAC).

• Possible values:

  • An empty string, representing power-control disabled.

  • “DRAC”: Lets you specify Dell DRAC. To use DRAC, you must have already installed the Dell supplemental pack.

  • “wake-on-lan”: Lets you specify Wake on LAN.

  • Any other name (used to specify a custom power-on script). This option is used to specify a custom script for power management.

• Type: string

host.power_on_config

• Definition: Contains key/value pairs for mode configuration. Provides additional information for DRAC.

• Possible values:

  • If you configured DRAC as the type of remote-power solution, you must also specify one of the following keys:

    • “power_on_ip”: The IP address you specified configured to communicate with the power-control card. Alternatively, you can type the domain name for the network interface where DRAC is configured.

    • “power_on_user”: The DRAC user name associated with the management processor, which you may have changed from its factory default settings.

    • “power_on_password_secret”: Specifies using the secrets feature to secure your password.

  • To use the secrets feature to store your password, specify the key “power_on_password_secret”. For more information, see Secrets.

• Type: Map (string, string)

Sample script

The sample script imports the Citrix Hypervisor API, defines itself as a custom script, and then passes parameters specific to the host you want to control remotely. You must define the parameters session in all custom scripts.

The result appears when the script is unsuccessful.

import XenAPI
def custom(session,remote_host,
power_on_config):
result="Power On Not Successful"
for key in power_on_config.keys():
result=result+''
key=''+key+''
value=''+power_on_config[key]
return result
<!--NeedCopy-->

Note:

After creating the script, save it in /etc/xapi.d/plugins with a .py extension.

Communicate with Citrix Hypervisor servers and resource pools

TLS

Citrix Hypervisor uses the TLS 1.2 protocol to encrypt management API traffic. Any communication between Citrix Hypervisor and management API clients (or appliances) uses the TLS 1.2 protocol.

Important:

We do not support customer modifications to the cryptographic functionality of the product.

Citrix Hypervisor uses the following cipher suite:

• TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384

In addition, the following cipher suites are also supported for backwards compatibility with some versions of Citrix Virtual Apps and Desktops:

• TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
• TLS_RSA_WITH_AES_256_CBC_SHA256
• TLS_RSA_WITH_AES_128_CBC_SHA256

Note:

These additional cipher suites use CBC mode. Although some organizations prefer GCM mode, Windows Server 2012 R2 does not support RSA cipher suites with GCM mode. Clients running on Windows Server 2012 R2 that connect to a Citrix Hypervisor server or pool, might need to use these CBC-mode cipher suites.

SSH

When using an SSH client to connect directly to the Citrix Hypervisor server the following algorithms can be used:

Ciphers:

• aes128-ctr
• aes256-ctr
• aes128-gcm@openssh.com
• aes256-gcm@openssh.com
• aes128-cbc
• aes256-cbc

MACs:

• hmac-sha2-256
• hmac-sha2-512
• hmac-sha1

KexAlgorithms:

• curve25519-sha256
• ecdh-sha2-nistp256
• ecdh-sha2-nistp384
• ecdh-sha2-nistp521
• diffie-hellman-group14-sha1

HostKeyAlgorithms:

• ecdsa-sha2-nistp256
• ecdsa-sha2-nistp384
• ecdsa-sha2-nistp521
• ssh-ed25519
• ssh-rsa

If you want to disable SSH access to your Citrix Hypervisor server, you can do this in xsconsole.

1. From XenCenter, open the server console and log in as root.
2. Type xsconsole.

3. In xsconsole, go to Remote Service Configuration > Enable/Disable Remote Shell.

   The console displays whether remote shell is enabled.

4. To change whether the remote shell is enabled or disabled, press Enter.

Important:

We do not support customer modifications to the cryptographic functionality of the product.

Install a TLS certificate on your server

The Citrix Hypervisor server comes installed with a default TLS certificate. However, to use HTTPS to secure communication between Citrix Hypervisor and Citrix Virtual Apps and Desktops, install a certificate provided by a trusted certificate authority.

This section describes how to install certificates by using the xe CLI. For information about working with certificates by using XenCenter, see the XenCenter documentation.

Ensure that your TLS certificate and its key meet the following requirements:

• The certificate and key pair are an RSA key.
• The key matches the certificate.
• The key is provided in a separate file to the certificate.
• The certificate is provided in a separate file to any intermediate certificates.
• The key file must be one of the following types: .pem or .key.
• Any certificate files must be one of the following types: .pem, .cer, or .crt.
• The key is greater than or equal to 2048 bits and less than or equal to 4096 bits in length.
• The key is an unencrypted PKCS #8 key and does not have a passkey.
• The key and certificate are in base-64 encoded ‘PEM’ format.
• The certificate is valid and has not expired.
• The signature algorithm is SHA-2 (SHA256).

The xe CLI warns you when the certificate and key you choose do not meet these requirements.

Where do I get a TLS certificate?

• You might already have a trusted certificate that you want to install on your Citrix Hypervisor server.

• Alternatively, you can create a certificate on your server and send it to your preferred certificate authority to be signed. This method is more secure as the private key can remain on the Citrix Hypervisor server and not be copied between systems.

  Creating a TLS certificate has the following steps:

  1. Generate a certificate signing request
  2. Send the certificate signing request to a certificate authority
  3. Install the signed certificate on your Citrix Hypervisor server

1. Generate a certificate signing request

First, generate a private key and certificate signing request. On the Citrix Hypervisor server, complete the following steps:

1. To create a private key file, run the following command:

   openssl genrsa -des3 -out privatekey.pem 2048
   <!--NeedCopy-->
   

2. Remove the password from the key:

   openssl rsa -in privatekey.pem -out privatekey.nop.pem
   <!--NeedCopy-->
   

3. Create the certificate signing request by using the private key:

   openssl req -new -key privatekey.nop.pem -out csr
   <!--NeedCopy-->
   

4. Follow the prompts to provide the information necessary to generate the certificate signing request.

   • Country Name. Enter the TLS Certificate country codes for your country. For example, CA for Canada or JM for Jamaica. You can find a list of TLS Certificate country codes on the web.
   • State or Province Name (full name). Enter the state or province where the pool is located. For example, Massachusetts or Alberta.
   • Locality Name. The name of the city where the pool is located.
   • Organization Name. The name of your company or organization.
   • Organizational Unit Name. Enter the department name. This field is optional.
   • Common Name. Enter the FQDN of your Citrix Hypervisor server. Citrix recommends specifying either an FQDN or an IP address that does not expire.
   • Email Address. This email address is included in the certificate when you generate it.

   The certificate signing request is saved in the current directory and is named csr.

5. Display the certificate signing request in the console window by running the following command:

   cat csr
   <!--NeedCopy-->
   

6. Copy the entire certificate signing request and use this information to request the certificate from the certificate authority.

   Example certificate signing request:

   -----BEGIN CERTIFICATE REQUEST-----
   MIIDBDCCAewCAQAwgYsxCzAJBgNVBAYTAlVLMRcwFQYDVQQIDA5DYW1icmlkZ2Vz
   aGlyZTESMBAGA1UEBwwJQ2FtYnJpZGdlMRIwEAYDVQQKDAlYZW5TZXJ2ZXIxFTAT
   ...
   SdYCkFdo+85z8hBULFzSH6jgSP0UGQU0PcfIy7KPKyI4jnFQqeCDvLdWyhtAx9gq
   Fu40qMSm1dNCFfnACRwYQkQgqCt/RHeUtl8srxyZC+odbunnV+ZyQdmLwLuQySUk
   ZL8naumG3yU=
   -----END CERTIFICATE REQUEST-----
   <!--NeedCopy-->
   

2. Send the certificate signing request to a certificate authority

Now that you have generated the certificate signing request, you can submit the request to your organization’s preferred certificate authority.

A certificate authority is a trusted third-party that provides digital certificates. Some certificate authorities require the certificates to be hosted on a system that is accessible from the internet. We recommend not using a certificate authority with this requirement.

The certificate authority responds to your signing request and provides the following files:

• the signed certificate
• if applicable, an intermediate certificate

You can now install all these files on your Citrix Hypervisor server.

3. Install the signed certificate on your Citrix Hypervisor server

After the certificate authority reponds to the certificate signing request, complete the following steps to install the certificate on your Citrix Hypervisor server:

1. Get the signed certificate and, if the certificate authority has one, the intermediate certificate from the certificate authority.
2. Copy the key and certificates to the Citrix Hypervisor server.

3. Run the following command on the server:

   xe host-server-certificate-install certificate=<path_to_certificate_file> private-key=<path_to_private_key> certificate-chain=<path_to_chain_file>
   

   The certificate-chain parameter is optional.

For additional security, you can delete the private key file after the certificate is installed.

Manage the administrator password

When you first install a Citrix Hypervisor server, you set an administrator or root password. You use this password to connect XenCenter to your server or (with user name root) to log into xsconsole, the system configuration console.

If you join a server to a pool, the administrator password for the server is automatically changed to match the administrator password of the pool master.

Note:

Citrix Hypervisor administrator passwords must contain only printable ASCII characters.

Change the password

You can use XenCenter, the xe CLI, or xsconsole to change the administrator password.

XenCenter

To change the administrator password for a pool or standalone server by using XenCenter, complete the following steps:

1. In the Resources pane, select the pool or any server in the pool.
2. On the Pool menu or on the Server menu, select Change Server Password.

To change the root password of a standalone server, select the server in the Resources pane, and click Password and then Change from the Server menu.

If XenCenter is configured to save your server login credentials between sessions, the new password is remembered. For more information, see Store your server connection state.

After changing the administrator password, rotate the pool secret. For more information, see Rotate the pool secret.

xe CLI

To change the administrator password by using the xe CLI, run the following command on a server in the pool:

  xe user-password-change new=<new_password>
<!--NeedCopy-->

Note:

Ensure that you prefix the command with a space to avoid storing the plaintext password in the command history.

After changing the administrator password, rotate the pool secret. For more information, see Rotate the pool secret.

xsconsole

To change the administrator password for a pool or a standalone server by using xsconsole, complete the following steps:

1. On the pool master, go to the console.
2. Log in as root.
3. Type xsconsole. Press Enter. The xsconsole is displayed.
4. In xsconsole, use the arrow keys to navigate to the Authentication option. Press Enter.
5. Navigate to Change Password. Press Enter.
6. Authenticate with the administrator password.
7. In the Change Password dialog:
   1. Enter your current password.
   2. Enter a new password.
   3. Enter the new password again to confirm it.

   The Password Change Successful screen is displayed. Press Enter to dismiss.

If the server is pool master, this updated password is now propagated to the other servers in the pool.

After changing the administrator password, rotate the pool secret. For more information, see Rotate the pool secret.

Reset a lost root password

If you lose the administrator (root) password for your Citrix Hypervisor server, you can reset the password by accessing the server directly.

1. Reboot the Citrix Hypervisor server.

2. When the GRUB menu shows, press e to edit the boot menu entry.

3. Add init=/sysroot/bin/sh to the line that starts with module2.

4. Press Ctrl-X to boot into a root shell.

5. At the command shell, run the following commands:

   chroot /sysroot
   passwd
   
   (type the new password twice)
   
   sync
   /sbin/reboot -f
   <!--NeedCopy-->
   

If the server is pool master, this updated password is now propagated to the other servers in the pool.

After changing the administrator password, rotate the pool secret.

Rotate the pool secret

The pool secret is a secret shared among the servers in a pool that enables the server to prove its membership to a pool.

Because users with the Pool Admin role can discover this secret, it is good practice to rotate the pool secret if one of these users leaves your organization or loses their Pool Admin role.

You can rotate the pool secret by using XenCenter or the xe CLI.

XenCenter

To rotate the pool secret for a pool by using XenCenter, complete the following steps:

1. In the Resources pane, select the pool or any server in the pool.
2. On the Pool menu, select Rotate Pool Secret.

When you rotate the pool secret, you are also prompted to change the root password. If you rotated the pool secret because you think that your environment has been compromised, ensure that you also change the root password. For more information, see Change the password.

xe CLI

To rotate the pool secret by using the xe CLI, run the following command on a server in the pool:

xe pool-secret-rotate
<!--NeedCopy-->

If you rotated the pool secret because you think that your environment has been compromised, ensure that you also change the root password. For more information, see Change the password.

Enable IGMP snooping on your Citrix Hypervisor pool

Citrix Hypervisor sends multicast traffic to all guest VMs leading to unnecessary load on host devices by requiring them to process packets they have not solicited. Enabling IGMP snooping prevents hosts on a local network from receiving traffic for a multicast group they have not explicitly joined, and improves the performance of multicast. IGMP snooping is especially useful for bandwidth-intensive IP multicast applications such as IPTV.

Notes:

• IGMP snooping is available only when the network back-end uses Open vSwitch.

• When enabling this feature on a pool, it may also be necessary to enable IGMP querier on one of the physical switches. Or else, multicast in the sub network falls back to broadcast and may decrease Citrix Hypervisor performance.

• When enabling this feature on a pool running IGMP v3, VM migration or network bond failover results in IGMP version switching to v2.

• To enable this feature with a GRE network, users must set up an IGMP Querier in the GRE network. Alternatively, you can forward the IGMP query message from the physical network into the GRE network. Or else, multicast traffic in the GRE network can be blocked.

You can enable IGMP snooping on a pool by using XenCenter or the xe CLI.

XenCenter

1. Navigate to Pool Properties.
2. Select Network Options. Here you can enable or disable IGMP snooping.

xe CLI

1. Get the pool UUID:

   xe pool-list

2. Enable/disable IGMP snooping for the pool:

   xe pool-param-set [uuid=pool-uuid] [igmp-snooping-enabled=true|false]

After enabling IGMP snooping, you can view the IGMP snooping table using the xe CLI.

View the IGMP snooping table

Use the following command to view the IGMP snooping table:

ovs-appctl mdb/show [bridge name]

Note:

You can get the bridge name using xe network-list. These bridge names can be xenbr0, xenbr1, xenapi, or xapi0.

This outputs a table with four columns:

• port: The port of the switch (OVS).
• VLAN: The VLAN ID of the traffic.
• GROUP: The multicast group that the port solicited.
• Age: The age of this record in seconds.

If the GROUP is a multicast group address, this means an IGMP Report message was received on the associated switch port. This means that a receiver (member) of the multicast group is listening on this port.

Take the following example which contains two records:

The first record shows that there is a receiver listening on port 14 for the multicast group 227.0.0.1. The Open vSwitch forwards traffic destined for the 227.0.0.1 multicast group to listening ports for this group only (in this example, port 14), rather than broadcasting to all ports. The record linking port 14 and group 227.0.0.1 was created 15 seconds ago. By default, the timeout interval is 300 seconds. This means that if the switch does not receive any further IGMP Report messages on port 14 for 300 seconds after adding the record, the record expires and is removed from the table.

In the second record, the GROUP is querier, meaning that IGMP Query messages have been received on the associated port. A querier periodically sends IGMP Query messages, which are broadcasted to all switch ports, to determine which network nodes are listening on a multicast group. Upon receiving an IGMP Query message, the receiver responds with an IGMP Report message, which causes the receiver’s multicast record to refresh and avoid expiration.

The VLAN column indicates to the VLAN that a receiver/querier lives. ‘0’ means native VLAN. If you want to run multicast on some tagged VLAN, ensure that there are records on the VLAN.

Note:

For the VLAN scenario, you should have a querier record with a VLAN column value equal to the VLAN ID of the network, otherwise multicast won’t work in the VLAN network.