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XenServer 7.3 and NFS

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Took me all day to figure this out. Xen 7.3 does not come with NFS support oddly. So you need to install it.

First you will surely need the epel repository

yum --enablerepo=extras install epel-release

Now you can install other packages.

yum --enablerepo=epel --enablerepo=base install nfs-utils

I also like MC so let’s install that too.

yum --enablerepo=epel --enablerepo=base install mc

Some useful commends to test NFS.

rpcinfo -s <IP>
showmount -e <IP>
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Citrix XenServer backup without downtime.

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Backup running Virtual Machine in XenServer. I am working with Citrix XenServer for many years and managing all XenServers using XenCenter installed on a standalone windows machine. We regularly take backup of VMs manually until today, I always take backups after shutting down the VM. Most of VM owner getting disappointed due to server down for a long time. While searching for the Google I found a better way to back up VMs without shutdown them. It means we can take running VM backups and not downtime occurred.


This tutorial we will help you step by step backup process of running VM. Also here is a shell script which can take all VMs backup or specified VM backup, which we can schedule through crontab as well.

Method 1 – Manual Backup of Running VM

Following steps also can be performed through XenCenter, But Linux lovers love the command line. So find commands to do it.

1.1. Find VMs UUID

Use the following command to get list of UUIDs of all vms along with other details. this UUID will be used in next step

xe vm-list is-control-domain=false is-a-snapshot=false

Sample Output:

uuid ( RO)           : 8ac95696-94f3-83c1-bc89-8bb2603f832b
     name-label ( RW): test-vm
    power-state ( RO): running

As per above output test-vm uuid is “8ac95696-94f3-83c1-bc89-8bb2603f832b“. It can be different in your case.

1.2. Create VMs Snapshot

Now use the following command to create snapshot of vm using uuid found in above step. Make sure you are using correct uuid.

xe vm-snapshot uuid=8ac95696-94f3-83c1-bc89-8bb2603f832b new-name-label=testvmsnapshot

Above command will retrun a UUID of snapshot, Use that UUID to convert snapshot to a vm, so we can export it to file using below command.

xe template-param-set is-a-template=false ha-always-run=false uuid=b15c0531-88a5-98a4-e484-01bc89131561

1.3. Export Snapshot to File

Now we can export created snapshot to .xva file, Which can be easily restored from command line or XenCenter.

xe vm-export vm=b15c0531-88a5-98a4-e484-01bc89131561 filename=vm-backup.xva

1.4. Destroy Snapshot

Finally as we have already taken backup to xva file, so we can destroy created snapshot from xenserver.

xe vm-uninstall uuid=b15c0531-88a5-98a4-e484-01bc89131561 force=true

Method 2 – Using Script for Backup Running VMs

To backup all VMs running on XenServer, we can use following shell script also. This script mounted remote file system exported through NFS. This script works for me perfectly, but it may not for you. So use this script at your own risk.

# Written By: Mr Rahul Kumar
# Created date: Jun 14, 2014
# Last Updated: Mar 08, 2017
# Version: 1.2.1
# Visit:

DATE=`date +%d%b%Y`

### Create mount point

mkdir -p ${MOUNTPOINT}

### Mounting remote nfs share backup drive

[ ! -d ${MOUNTPOINT} ]  && echo "No mount point found, kindly check"; exit 0

mkdir -p ${BACKUPPATH}
[ ! -d ${BACKUPPATH} ]  && echo "No backup directory found"; exit 0

# Fetching list UUIDs of all VMs running on XenServer
xe vm-list is-control-domain=false is-a-snapshot=false | grep uuid | cut -d":" -f2 > ${UUIDFILE}

[ ! -f ${UUIDFILE} ] && echo "No UUID list file found"; exit 0

while read VMUUID
    VMNAME=`xe vm-list uuid=$VMUUID | grep name-label | cut -d":" -f2 | sed 's/^ *//g'`

    SNAPUUID=`xe vm-snapshot uuid=$VMUUID new-name-label="SNAPSHOT-$VMUUID-$DATE"`

    xe template-param-set is-a-template=false ha-always-run=false uuid=${SNAPUUID}

    xe vm-export vm=${SNAPUUID} filename="$BACKUPPATH/$VMNAME-$DATE.xva"

    xe vm-uninstall uuid=${SNAPUUID} force=true

done < ${UUIDFILE}

umount ${MOUNTPOINT}

Download this script directly from

Posted in Linux, Virtualization, XenServer 2 Comments

XenServer Limit with socket vs vCPU in windows

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The problem is that XenServer virtualises each core as a separate physical processor in its own socket. Windows Server 2008 and 2003 are limited to 4 sockets, so you can only see 4 of your 8 cores in the task manager.

If you look in the Device Manger you’ll see all 8 cores because Windows sees them all, but won’t let you use them.

If you look in the XenServer Host console in the Hardware section, it will report 8 physical CPUs too.

In XenCenter set the VCPUs for your VM to 2.

Then enter the attached code snipped into the XenServer Host console. To find the UUID for your VM, type:

xe vm-list

xe vm-param-set platform:cores-per-socket=4 uuid=xxxxxx

xe vm-param-set VCPUs-max=8 uuid=xxxxxxx

xe vm-param-set VCPUs-at-startup=8 uuid=xxxxxx

Now boot the VM and the task manager should show all 8 cores.

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