Tag Archives: azure

Prepare a RHEL-Based Virtual Machine for Azure

Today we have got project to prepare RHEL  VHD’s  for Azure. I did not find any doc for RHEL on azure. So i think to write steps i followed for RHEL on azure …


CentOS Installation Notes

  • The newer VHDX format is not supported in Azure. You can  convert the disk to VHD format using Hyper-V Manager or the convert-vhd cmdlet.
  • When installing the Linux system it is recommended that you use standard partitions rather than LVM (often the default for many installations). This will avoid LVM name conflicts with cloned VMs, particularly if an OS disk ever needs to be attached to another VM for troubleshooting. LVM or RAID may be used on data disks if preferred.
  • NUMA is not supported for larger VM sizes due to a bug in Linux kernel versions below 2.6.37. This issue primarily impacts distributions using the upstream Red Hat 2.6.32 kernel. Manual installation of the Azure Linux agent (waagent) will automatically disable NUMA in the GRUB configuration for the Linux kernel. More information about this can be found in the steps below.
  • Do not configure a swap partition on the OS disk. The Linux agent can be configured to create a swap file on the temporary resource disk. More information about this can be found in the steps below.
  • All of the VHDs must have sizes that are multiples of 1 MB.

RHEL 6.5

  1. In Hyper-V Manager, select the virtual machine.
  2. Click Connect to open a console window for the virtual machine.
  3. Uninstall NetworkManager by running the following command:
    # sudo rpm -e --nodeps NetworkManager

    Note: If the package is not already installed, this command will fail with an error message. This is expected.

  4. Create a file named network in the /etc/sysconfig/ directory that contains the following text:
  5. Create a file named ifcfg-eth0 in the /etc/sysconfig/network-scripts/ directory that contains the following text:
  6. Move (or remove) udev rules to avoid generating static rules for the Ethernet interface. These rules cause problems when cloning a virtual machine in Microsoft Azure or Hyper-V:
    # sudo mkdir -m 0700 /var/lib/waagent
    # sudo mv /lib/udev/rules.d/75-persistent-net-generator.rules /var/lib/waagent/
    # sudo mv /etc/udev/rules.d/70-persistent-net.rules /var/lib/waagent/
  7. Ensure the network service will start at boot time by running the following command:
    # sudo chkconfig network on
  8. Install the python-pyasn1 package by running the following command:
    # sudo yum install python-pyasn1
  9. If you would like to use the OpenLogic mirrors that are hosted within the Azure datacenters, then replace the /etc/yum.repos.d/CentOS-Base.repo file with the following repositories. This will also add the [openlogic] repository that includes packages for the Azure Linux agent:
    name=CentOS-$releasever - openlogic packages for $basearch
    name=CentOS-$releasever - Base

    Note: The rest of this guide will assume you are using at least the [openlogic] repo, which will be used to install the Azure Linux agent below.

  10. Add the following line to /etc/yum.conf:
  11. Run the following command to clear the current yum metadata:
    # yum clean all
  12. Modify the kernel boot line in your grub configuration to include additional kernel parameters for Azure. To do this open “/boot/grub/menu.lst” in a text editor and ensure that the default kernel includes the following parameters:
    console=ttyS0 earlyprintk=ttyS0 rootdelay=300 numa=off


    This will also ensure all console messages are sent to the first serial port, which can assist Azure support with debugging issues. This will disable NUMA due to a bug in the kernel version used by RHEL 6.azure_kernel

    In addition to the above, it is recommended to remove the following parameters:

    rhgb quiet crashkernel=auto

    Graphical and quiet boot are not useful in a cloud environment where we want all the logs to be sent to the serial port.

    The crashkernel option may be left configured if desired, but note that this parameter will reduce the amount of available memory in the VM by 128MB or more, which may be problematic on the smaller VM sizes.

  13. Ensure that the SSH server is installed and configured to start at boot time. This is usually the default.
  14. Disable SWAP  :  comment swap in /etc/fstab
        # blkid | grep swap
      /dev/sda3: UUID="53-e0e3efe22612" TYPE="swap"
      # swapoff /dev/sda3
  15. Install the Azure Linux Agent by running the following command:
    # sudo yum install WALinuxAgent

    Note that installing the WALinuxAgent package will remove the NetworkManager and NetworkManager-gnome packages if they were not already removed as described in step 2.

  16. Do not create swap space on the OS diskThe Azure Linux Agent can automatically configure swap space using the local resource disk that is attached to the VM after provisioning on Azure. Note that the local resource disk is a temporary disk, and might be emptied when the VM is deprovisioned. After installing the Azure Linux Agent (see previous step), modify the following parameters in /etc/waagent.conf appropriately:
    ResourceDisk.SwapSizeMB=8192    ## NOTE: set this to whatever you need it to be.
  17. Run the following commands to deprovision the virtual machine and prepare it for provisioning on Azure:
    # sudo waagent -force -deprovision
    # export HISTSIZE=0
    # logout
  18. Click Action -> Shut Down in Hyper-V Manager. Your Linux VHD is now ready to be uploaded to Azure.

Microsoft Azure Set a Static Internal IP Address for a VM

Before you specify a static IP address from your address pool, you may want to verify that the IP address has not been already assigned. In the example below, we’re checking to see whether the IP address is available in the TestVNet virtual network.

Test-AzureStaticVNetIP –VNetName TestVNet –IPAddress 

Be sure to change the variables for the cmdlets to reflect what you require for your environment before running them.

New-AzureVMConfig -Name $vmname -ImageName $img –InstanceSize Small | Set-AzureSubnet –SubnetNames $sub | Set-AzureStaticVNetIP -IPAddress | New-AzureVM –ServiceName $vmsvc1 –VNetName TestVNet

If you want to set a static IP address for a VM that you previously created, you can do so by using the following cmdlets. If you already set an IP address for the VM and you want to change it to a different IP address, you’ll need to remove the existing static IP address before running these cmdlets. See the instructions below to remove a static IP.

For this procedure, you’ll use the Update-AzureVM cmdlet. The Update-AzureVM cmdlet restarts the VM as part of the update process. The DIP that you specify will be assigned after the VM restarts. In this example, we set the IP address for VM2, which is located in cloud service StaticDemo.

Get-AzureVM -ServiceName StaticDemo -Name VM2 | Set-AzureStaticVNetIP -IPAddress | Update-AzureVM

When you remove a static IP address from a VM, the VM will automatically receive a new DIP after the VM restarts as part of the update process. In the example below, we remove the static IP from VM2, which is located in cloud service StaticDemo.

Get-AzureVM -ServiceName StaticDemo -Name VM2 | Remove-AzureStaticVNetIP | Update-AzureVM