This article describes how to configure Control Domain (dom0) memory in XenServer 6.1.0 or later.

Administrative access to a XenServer host console either directly, via SSH, or by using the Console tab in XenCenter.

Steps:

1. On the XenServer host, open a local shell and login as root.

2. Enter the following command:

    /opt/xensource/libexec/xen-cmdline –set-xen dom0_mem=M,max:M

   NOTE:  represents the the amount of memory, in megabytes, to be allocated to dom0. This value should be between 1024 and 4096, depending on the number of VMs that are expected to run and the total amount of memory of the host. A higher value will result in less memory being available to the VMs.

3. Restart the XenServer host using XenCenter or the reboot command on the console.After the host has been rebooted, run the command, free on the console to verify the new memory settings.

NOTE: On smaller memory machines (less than 16GiB), some customers may wish to reduce the memory allocated to dom0 below the default of 752MiB. Customers can follow the above procedure to reduce the dom0 memory. However, Citrix recommends that you do not reduce the dom0 memory below 400MB.

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