How to Manage RedHat Enterprise Virtualization (RHEV) Virtual Machines Operations and Tasks – Part 6

In this part of our tutorial we are going to discuss the operations and tasks such as Taking Snaphots, Creating Pools, Making Templates and Cloning are the main operations which could be performed on...

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In this part of our tutorial we are going to discuss the operations and tasks such as Taking Snaphots, Creating Pools, Making Templates and Cloning are the main operations which could be performed on RHEV virtual machines hosted by RHEV environment.

Before going further, I request you to read the rest of the articles from this RHEV series here:

RedHat Enterprise Virtualization (RHEV) Administration Series – Part 1-7

Manage RHEV VM Operations and Tasks

Manage RHEV VM Operations and Tasks – Part 6

Snapshots

Snapshot is used to save VM’s state at specific Point-Time. This is very useful and helpful during software testing process or revert something going wrong on your system as you could return back to the Point-Time which you took snapshot at.

1. Start your linux-vm machine and verify the OS version and type before taking snapshot.

Check Linux OS Version

Img 01: Check Linux OS Version


2. Click on “Create Snapshot”.

Create RHEV Snapshot

Img 02: Create RHEV Snapshot

3. Add the description and select disks and saving memory then OK.

Add Snapshot Description

Img 03: Add Snapshot Description

Check the status of snapshot and task status from tasks bar.

Confirm Created Snapshot Status

Img 04: Confirm Created Snapshot Status

After finishing, you will note that status of snapshot changed from Lock to OK, which meaning that your snapshot is ready and created successfully.

Check Snapshot Status

Img 05: Check Snapshot Status

4. Lets go to the VM console and delete /etc/issue file.

Delect Issue File

Img 06: Delete Issue File

5. For reverting/restoring process, your virtual machine should be at down state. Make sure its powered off and then click “Preview” to check the snapshot and reverting on-fly to it.

Shut Down Snapshot

Img 07: Shut Down Snapshot

Now confirm Memory restoring.

Restore Snapshot Memory

Img 08: Restore Snapshot Memory

Wait for Previewing to be finished and after few minuets, you will noted that snapshot status is “In preview”.

Snapshot In Preview State

Img 09: Snapshot In Preview State

Now we have two ways:

6. First one to directly “Commit” the restored snapshot to the original virtual machine and finishing the total reverting process.

Second one to check the reverted changes before commit the restored snapshot to original vm. After checking we will go to the first way “Commit”.

For this article, we will start via second way. So, we will need to power up the virtual machine and then check the /etc/issue file. You will find it without any changes.

Check Issue File

Img 10: Check Issue File

7. Your VM should be powered off for reverting process. After powering off, Commit your snapshot to vm.

Commit VM Snapshot

Img 11: Commit VM Snapshot

Then watch restoring commit process, after finishing commit process, you will find snapshot status is “OK”.

Confirm Commit Snapshot

Img 12: Confirm Commit Snapshot

Hints : 1. If you don’t want to confirm reverting to snapshot after preview stage, just click on “Undo” to skip snapshot. Its always recommended to take snapshot of power down VM instead of be running. You can create new VM from current snapshot, just select your preferred snapshot and click on “Clone”.

Create VM Snapshot Clone

Img 13: Create VM Snapshot Clone

Templates:

Actually, template is a very normal virtual machine copy, but without any pre-configuration related to the original vm operating system. Templates are used to improve the speed and decrease time of vm operating system installation.

Creating templates has two main process:
  1. A. Sealing the original virtual machine.
  2. B. Taking copy [Create Template] of the sealed vm to be separated template.

A. Sealing Process:

To seal RHEL6 Virtual Machine you should make sure about this points :

8. Flagging system for pre-configuration for next booting by creating this empty hidden file.

# touch /.unconfigured

9. Remove any ssh host keys and set hostname to be localhost.localdomain in /etc/sysconfig/network file and also remove system udev rules.

# rm -rf /etc/ssh/ssh_host_*
# rm -rf /etc/udev/rules.d/70-*

10. Remove MAC address from Network interface configuration file eg. [/etc/sysconfig/network-scripts/ifcfg-eth0] and delete all system logs under /var/log/ and finally Power off your virtual machine.

Commands to Follow

Img 14: Commands to Follow

B. Creating Templates

11. Select the sealed vm and click “Create Template”.

Create New VM Template

Img 15: Create New VM Template

12. Provide details and proprieties about your new template.

Add Template Details

Img 16: Add Template Details

Now, you can check the process from tasks and also you could switch Templates tab to monitor the status of your new templates.

Check Template Information

Img 16: Check Template Information

Monitor Template Status

Img 17: Monitor Template Status

Wait a few minutes, then check template status again.

Check VM Template Again

Img 18: Check VM Template Again

You will note that its converted from lock to OK. Now our new template is ready to be used. Actually we will use it in the next section.

Creating Pools:

Pool is a group of identical virtual machines. Pooling is used to create a given number of identical virtual machines in one step. Those virtual machines could be based on pre-created template.

Creating New Pool

13. Switch to Pools tab and click New then fill the appeared wizard windows.

Create New Pool

Img 19: Create New Pool

14. Now check the status of created Pool vms and wait few minutes, you will note the status of virtual machines changed from Lock to Down.

VM Pool Status Locked

Img 20: VM Pool Status Locked

VM Pool Status Down

Img 21: VM Pool Status Down

You could also check the status from Virtual Machines tab.

Check Pool Status from VM

Img 22: Check Pool Status from VM

15. Lets try to run one of Pool virtual machines.

Run Virtual Machine

Img 22: Run Virtual Machine

That’s right, you will be asked for new root password and also you will be asked about basic authentication configuration. Once finished your new vm is now ready for use.

Select Basic Authentication

23: Select Basic Authentication

Monitor VMs also from pools tab.

Monitor Virtual Machine

Img 24: Monitor Virtual Machine

Notes:

  1. To delete Pool, You should detach all of VMs from the Pool.
  2. To detach VM from Pool, VM must be at down state.
  3. Compare VM installation time [Normal way VS. Template using].

Create VM Clones:

Cloning is normal Copy Process without any change to the Original Source. Cloning could done from Original VM or Snapshot.

To take Clone:

16. Select the Original source [VM or Snapshot] then click “Clone VM”.

Create VM Clone

Img 25: Create VM Clone

Hint: If you will take clone from VM, VM must be at down state.

17. Provide name to your cloned VM and wait few minutes, you will find the cloning process is done and the new vm now is ready to be used.

Give VM Clone Name

Img 26: Give VM Clone Name

VM Clone Details

Img 27: VM Clone Details

Conclusion

As a RHEV administrator, there some main tasks to be done on environment virtual machines. Cloning, Creating Pools, Making Templates and Taking snapshots are basic and important tasks should be done by RHEV admin. This tasks also considered as the core tasks of any virtualization environment, So make sure you understood it well then do more and more,,, and more practical labs in your private environment.

Resources: RHEV Administration Guide

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