Rediger

Del via

Prepare an Oracle Linux virtual machine for Azure

  • Artikkel

Applies to: ✔️ Linux VMs ✔️ Flexible scale sets

This article assumes that you've already installed an Oracle Linux operating system (OS) to a virtual hard disk (VHD). Multiple tools exist to create .vhd files. An example is a virtualization solution such as Hyper-V. For instructions, see Install the Hyper-V role and configure a virtual machine (VM).

Oracle Linux installation notes

  • For more tips on preparing Linux for Azure, see General Linux installation notes.
  • Hyper-V and Azure support Oracle Linux with either the Unbreakable Enterprise Kernel (UEK) or the Red Hat Compatible Kernel.
  • Oracle's UEK2 isn't supported on Hyper-V and Azure because it doesn't include the required drivers.
  • The VHDX format isn't supported in Azure, only fixed VHD. You can convert the disk to VHD format by using Hyper-V Manager or the convert-vhd cmdlet.
  • Kernel support for mounting user-defined functions (UDF) file systems is required. At first boot on Azure, the provisioning configuration is passed to the Linux VM via UDF-formatted media that's attached to the guest. The Azure Linux agent must be able to mount the UDF file system to read its configuration and provision the VM.
  • When you install the Linux system, we recommend that you use standard partitions rather than Logical Volume Manager (LVM), which is often the default for many installations. These standard partitions 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 can also be used on data disks.
  • Linux kernel versions earlier than 2.6.37 don't support NUMA on Hyper-V with larger VM sizes. This issue primarily affects older distributions that use the upstream Red Hat 2.6.32 kernel and was fixed in Oracle Linux 6.6 and later.
  • Don't configure a swap partition on the OS disk.
  • All VHDs on Azure must have a virtual size aligned to 1 MB. When you convert from a raw disk to VHD, you must ensure that the raw disk size is a multiple of 1 MB before conversion. For more information, see Linux installation notes.
  • Make sure that the Addons repository is enabled. Edit the file /etc/yum.repos.d/public-yum-ol6.repo(Oracle Linux 6) or /etc/yum.repos.d/public-yum-ol7.repo(Oracle Linux 7). Change the line enabled=0 to enabled=1 under [ol6_addons] or [ol7_addons] in this file.

Oracle Linux 6.X

Important

Remember that Oracle Linux 6.x is already at end of life. Oracle Linux version 6.10 has available Extended Lifecycle Support, which ends July 2024.

You must complete specific configuration steps in the OS for the VM to run in Azure.

  1. In the center pane of Hyper-V Manager, select the VM.

  2. Select Connect to open the window for the VM.

  3. Uninstall NetworkManager:

    sudo rpm -e --nodeps NetworkManager

    Note

    If the package isn't already installed, this command fails with an error message. This message is expected.

  4. Create a file named network in the /etc/sysconfig/ directory that contains the following text:

    NETWORKING=yes
HOSTNAME=localhost.localdomain

  5. Create a file named ifcfg-eth0 in the /etc/sysconfig/network-scripts/ directory that contains the following text:

    DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
TYPE=Ethernet
USERCTL=no
PEERDNS=yes
IPV6INIT=no

  6. Modify udev rules to avoid generating static rules for the Ethernet interfaces. These rules can cause problems when you clone a VM in Azure or Hyper-V:

    sudo ln -s /dev/null /etc/udev/rules.d/75-persistent-net-generator.rules
sudo rm -f /etc/udev/rules.d/70-persistent-net.rules

  7. Ensure that the network service starts at boot time:

    sudo chkconfig network on

  8. Install python-pyasn1:

    sudo yum install python-pyasn1

  9. Modify the kernel boot line in your grub configuration to include more kernel parameters for Azure. To do this step, open /boot/grub/menu.lst in a text editor and ensure that the kernel includes the following parameters:

    console=ttyS0 earlyprintk=ttyS0

    This setting ensures that all console messages are sent to the first serial port, which can assist Azure support with debugging issues.

    In addition to the preceding steps, we recommend that you remove the following parameters:

    rhgb quiet crashkernel=auto

    Graphical and quiet boot aren't useful in a cloud environment where you want all the logs to be sent to the serial port.

    The crashkernel option can be left configured if you want. This parameter reduces the amount of available memory in the VM by 128 MB or more, which might be a problem for smaller VM sizes.

  10. Ensure that the SSH server is installed and configured to start at boot time. This setting is usually the default.

  11. Install the Azure Linux agent by running the following command. The latest version is 2.0.15.

    sudo yum install WALinuxAgent

    Installing the WALinuxAgent package removes the NetworkManager and NetworkManager-gnome packages if they weren't already removed, as described in step 2.

  12. Don't create swap space on the OS disk.

    The Azure Linux agent can automatically configure swap space by using the local resource disk that's attached to the VM after provisioning on Azure. The local resource disk is a temporary disk and might be emptied when the VM is deprovisioned. After you install the Azure Linux agent (see the previous step), modify the following parameters in /etc/waagent.conf appropriately:

    ResourceDisk.Format=y
ResourceDisk.Filesystem=ext4
ResourceDisk.MountPoint=/mnt
ResourceDisk.EnableSwap=y
ResourceDisk.SwapSizeMB=2048    ## NOTE: set this to whatever you need it to be.

  13. Deprovision the VM and prepare it for provisioning on Azure:

    sudo waagent -force -deprovision
sudo export HISTSIZE=0
sudo logout

  14. Select Action > Shut Down in Hyper-V Manager. Your Linux VHD is now ready to be uploaded to Azure.

Oracle Linux 7.0 and later

Follow the steps in the next sections if you're using Oracle Linux 7.0 or later.

Changes in Oracle Linux 7

Preparing an Oracle Linux 7 VM for Azure is similar to Oracle Linux 6, but several differences are worth noting:

  • Azure supports Oracle Linux with either the Unbreakable Enterprise Kernel (UEK) or the Red Hat Compatible Kernel. We recommend that you use Oracle Linux with UEK.
  • The NetworkManager package no longer conflicts with the Azure Linux agent. This package is installed by default, and we recommend that you don't remove it.
  • GRUB2 is now used as the default bootloader, so the procedure for editing kernel parameters has changed. (See the "Configuration steps" section.)
  • XFS is now the default file system. The ext4 file system can still be used if you want.

Configuration steps

  1. In Hyper-V Manager, select the VM.

  2. Select Connect to open a console window for the VM.

  3. Create a file named network in the /etc/sysconfig/ directory that contains the following text:

    NETWORKING=yes
HOSTNAME=localhost.localdomain

  4. Create a file named ifcfg-eth0 in the /etc/sysconfig/network-scripts/ directory that contains the following text:

    DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
TYPE=Ethernet
USERCTL=no
PEERDNS=yes
IPV6INIT=no

  5. Modify udev rules to avoid generating static rules for the Ethernet interfaces. These rules can cause problems when you clone a VM in Azure or Hyper-V:

    sudo ln -s /dev/null /etc/udev/rules.d/75-persistent-net-generator.rules

  6. Ensure that the network service starts at boot time:

    sudo chkconfig network on

  7. Install the python-pyasn1 package:

    sudo yum install python3-pyasn1

  8. Clear the current yum metadata and install any updates:

    sudo yum clean all
sudo yum -y update

  9. Modify the kernel boot line in your grub configuration to include more kernel parameters for Azure. To do this step, open /etc/default/grub in a text editor and edit the GRUB_CMDLINE_LINUX parameter. For example:

    GRUB_CMDLINE_LINUX="console=ttyS0 earlyprintk=ttyS0 net.ifnames=0"

    This modification also ensures that all console messages are sent to the first serial port, which can assist Azure support with debugging issues. It also turns off the naming conventions for network interface cards in Oracle Linux 7 with the UEK. We also recommend that you remove the following parameters:

       rhgb quiet crashkernel=auto

    Graphical and quiet boot aren't useful in a cloud environment where you want all the logs to be sent to the serial port.

    The crashkernel option can be left configured if you want. This parameter reduces the amount of available memory in the VM by 128 MB or more, which might be a problem for smaller VM sizes.

  10. After you're finished editing /etc/default/grub, rebuild the grub configuration:

    sudo grub2-mkconfig -o /boot/grub2/grub.cfg

  11. Ensure that the SSH server is installed and configured to start at boot time. This setting is usually the default.

  12. Install the Azure Linux agent and dependencies:

    sudo yum install WALinuxAgent
sudo systemctl enable waagent

  13. Install cloud-init to handle the provisioning:

    sudo yum install -y cloud-init cloud-utils-growpart gdisk hyperv-daemons

  14. Configure waagent for cloud-init:

    sudo sed -i 's/Provisioning.UseCloudInit=n/Provisioning.UseCloudInit=y/g' /etc/waagent.conf
sudo sed -i 's/Provisioning.Enabled=y/Provisioning.Enabled=n/g' /etc/waagent.conf

    sudo echo "Adding mounts and disk_setup to init stage"
sudo sed -i '/ - mounts/d' /etc/cloud/cloud.cfg
sudo sed -i '/ - disk_setup/d' /etc/cloud/cloud.cfg
sudo sed -i '/cloud_init_modules/a\\ - mounts' /etc/cloud/cloud.cfg
sudo sed -i '/cloud_init_modules/a\\ - disk_setup' /etc/cloud/cloud.cfg

    echo "Allow only Azure datasource, disable fetching network setting via IMDS"

    sudo cat > /etc/cloud/cloud.cfg.d/91-azure_datasource.cfg <<EOF
datasource_list: [ Azure ]
datasource:
    Azure:
        apply_network_config: False
EOF


if [[ -f /mnt/resource/swapfile ]]; then
echo Removing swapfile - Oracle Linux uses a swapfile by default
swapoff /mnt/swapfile
rm /mnt/swapfile -f
fi

echo "Add console log file"
cat >> /etc/cloud/cloud.cfg.d/05_logging.cfg <<EOF

# This tells cloud-init to redirect its stdout and stderr to
# 'tee -a /var/log/cloud-init-output.log' so the user can see output
# there without needing to look on the console.
output: {all: '| tee -a /var/log/cloud-init-output.log'}
EOF

  15. Swap configuration:

    1. Don't create swap space on the operating system disk.

      Previously, the Azure Linux agent was used automatically to configure swap space by using the local resource disk that's attached to the VM after the VM is provisioned on Azure. However, cloud-init now handles this step. You must not use the Linux agent to format the resource disk to create the swap file. Modify the following parameters in /etc/waagent.conf appropriately:

      sudo sed -i 's/ResourceDisk.Format=y/ResourceDisk.Format=n/g' /etc/waagent.conf
sudo sed -i 's/ResourceDisk.EnableSwap=y/ResourceDisk.EnableSwap=n/g' /etc/waagent.conf

    2. If you want to mount, format, and create the swap, you can either:

      • Pass this code in as a cloud-init configuration every time you create a VM.
      • Use a cloud-init directive baked into the image to do this step every time the VM is created:
      echo 'DefaultEnvironment="CLOUD_CFG=/etc/cloud/cloud.cfg.d/00-azure-swap.cfg"' >> /etc/systemd/system.conf
cat > /etc/cloud/cloud.cfg.d/00-azure-swap.cfg << EOF
#cloud-config
# Generated by Azure cloud image build
disk_setup:
  ephemeral0:
    table_type: mbr
    layout: [66, [33, 82]]
    overwrite: True
fs_setup:
  - device: ephemeral0.1
    filesystem: ext4
  - device: ephemeral0.2
    filesystem: swap
mounts:
  - ["ephemeral0.1", "/mnt/resource"]
  - ["ephemeral0.2", "none", "swap", "sw,nofail,x-systemd.requires=cloud-init.service,x-systemd.device-timeout=2", "0", "0"]
EOF

  16. Deprovision the VM and prepare it for provisioning on Azure:

    sudo cloud-init clean
sudo rm -f /var/log/waagent.log
sudo waagent -force -deprovision
sudo rm -f ~/.bash_history
sudo export HISTSIZE=0

    Note

    If you're migrating a specific VM and don't want to create a generalized image, skip the deprovision step.

  17. Select Action > Shut Down in Hyper-V Manager. Your Linux VHD is now ready to be uploaded to Azure.

Related content

You're now ready to use your Oracle Linux .vhd to create new VMs in Azure. If this is the first time that you're uploading the .vhd file to Azure, see Create a Linux VM from a custom disk.