Prepare the VMs for back up
This section describes the considerations and prerequisites to back up the VMs for restoring to a different cloud platform. The process is different for different operating systems, depending on the cloud service to which you want to restore.
Target: AWS
- Install the required Xen and Nitro drivers:
If drivers are not installed, then install them by running the following commands:
lsinitrd | grep -i -e nvme -e ena -e xen
modinfo nvme
For more information, refer to Install or upgrade the NVMe driver
modinfo ena
For more information, refer to Enable enhanced networking with the Elastic Network Adapter (ENA) on your EC2 instances
Update/Create the
/etc/dracut.conffile with the following line:add_drivers+="xen-blkfront xen-netfront nvme-core nvme"
Run the following command:
dracut -f -v
Validate if the drivers are installed successfully by running the following command:
lsinitrd | grep -i -e nvme -e ena -e xen
- To avoid mount failures, it is recommended to replace the device names with UUID in
/etc/fstabfile.Back up the original
fstabfile and comment out Azure-specific entries, and other non-critical entries which might cause boot failures after restore. Alternatively, you can addnofailinfstabfile for these entries. - Create a root user password.
- Configure or obtain the root user credentials, if the VM is configured with key based logon.
To use the key based logon, perform the following:
Back up the original
/root/.ssh/authorized_keys.The
/root/.ssh/authorized_keyscontains the same public key as azureuser, but cannot log on using the root user and key due to the following command present inauthorized_keysfor the root user and the associated key:`echo 'Please login as the user \"azureuser\" rather than the user \"root\".';echo;sleep 10;exit 142`
Note:
This is applicable for Azure-created keys and user-provided keys.
You must delete the command to let the root logon work after restore.
After editing, the entry appears as follows:
cat /root/.ssh/authorized_keys no-port-forwarding,no-agent-forwarding,no-X11-forwarding, ssh-rsa AAAAB3Nza..<truncated>..HruCzDsb3j
Target: Azure
- AWS instances have Hv and NVMe drivers preinstalled and hence no additional steps are required. Confirm if the drivers exist in your instance, run the command:
lsinitrd | grep -i -e hv -e nvme
- Replace the device names with UUID in
/etc/fstabfile.
Target: AWS
By default, AWS uses SUSE kernel. Hence install the SUSE kernel and select it at the boot time from the GRUB menu on the restored VM as follows:
- Refer to the following documentation for more information on entries in
zypp.conffile as it may affect the number of kernels retained and their behavior:Installing multiple kernel versions
Proceed with the next steps after ensuring that the SUSE computer can work with multiple kernels.
- Run the following command to list the available kernels:
zypper se -s 'kernel*'
- From the list of kernels displayed in the above step, install a suitable default kernel version:
zypper in kernel-default-<VERSION>
For example, zypper in kernel-default-5.3.18-53.3
- List the installed kernels and kernel modules using the following command:
zypper se -si 'kernel*'
- It is recommended to set a root user password.
- If the required drivers are not installed, then install them by running the following commands:
lsinitrd --kver <YOUR NEW KERNEL VERSION> | grep xen
Update/Create the
/etc/dracut.conffile with the following line:add_drivers+="xen-blkfront xen-netfront nvme-core nvme"
Run the following command:
dracut -f -v
dracut -f -v --kver <YOUR NEW KERNEL VERSION>
lsinitrd --kver <YOUR NEW KERNEL VERSION> | grep xen
<YOUR NEW KERNEL VERSION> is the new kernel version installed in Step 3 above.
- Back up the
/etc/default/grubfile. Edit the originalgrubfile, add GRUB_TIMEOUT and GRUB_TIMEOUT_STYLE entries and comment out the following parameters:GRUB_HIDDEN_TIMEOUT
GRUB_HIDDEN_TIMEOUT_QUIET
By default, GRUB_DEFAULT is set to 0 in the
/etc/default/grubfile. Change the default value so that it loads Azure kernel on restart and not the newly installed kernel.For example,
GRUB_DEFAULT='1>KERNEL_INDEX'where KERNEL_INDEX can be found with grub2-mkconfig command or by analyzing /boot/grub2/grub.cfgfile.Updating GRUB_DEFAULT ensures that the source VM keeps using Azure kernel, in an event, where it is restarted while the new kernel is installed.
The GRUB config file has entries similar to the following:
#GRUB_HIDDEN_TIMEOUT= #GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_DEFAULT'1><YOUR KERNEL INDEX NUMBER>' GRUB_TIMEOUT=20 GRUB_TIMEOUT_STYLE=menu
Update the GRUB config file using the following command:
grub2-mkconfig -o /boot/grub2/grub.cfg
After restore, to access GRUB menu during restart, press ESC twice during the countdown on EC2 Serial Console.
For more information on GRUB entries, refer to Simple configuration handling
Target: Azure
- Run the following command to verify if the drivers are preinstalled:
lsinitrd | grep -i -e hv -e nvme
- It is recommended to replace the device names with UUID in
/etc/fstabfile.
Target: AWS
- Run the following command to install the linux-aws kernel package:
sudo apt-get update && sudo apt-get upgrade -y linux-aws
- Change grub countdown style and increase time-out in
/etc/default/grubfile. This enables the user to enter the recovery mode if issues are faced during the restart:GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=20
- To avoid loading the new kernel on restart, ensure that the default kernel entry (GRUB_DEFAULT) in the grub configuration file is pointing to Azure-specific kernel and not the newly installed kernel.
- Run the following command to update
grubfile:update-grub
Target: Azure
- Run the following command to verify if the drivers are preinstalled:
lsinitrd | grep -i -e hv -e nvme
- It is recommended to replace the device names with UUID in
/etc/fstabfile.
Target: AWS
- Check the boot mode (Legacy or UEFI).
- Run the following:
(Ctrl + R) -> MSInfo32.exe → BIOS Mode
- Install the following drivers:
PV driver: AWSPVDriver.zip
EC2 install: EC2Install.zip
NVME: AWSNVMe.zip