Description

This page details several known issues with deploying a Snapshot Preview with RHEL, CentOS, or Oracle Operating Systems if the option to preserve MAC addresses is not chosen.

Description of Issue

When a new "Snapshot Preview" server is created from a Historical Snapshot and the option to preserve MAC addresses is not chosen, a UNIX-based Guest OS may need configuration changes because the underlying OS does not automatically recognize the new "Snapshot Preview" server's virtual hardware NICs due to the change in MAC addresses. The are two potential effects:

  • The ethernet config file may have the same Hardware Address (MAC Address) as the Source Snapshot Server. In order for the Guest OS to use the NIC, the Hardware Address (MAC Address) in the config file should match the Virtual NIC adapter's Hardware Address.
  • The 70-persistent-net.rules udev rule will tend to change the Ethernet Adapter name. For example, the Snapshot may have a configuration where a given NIC key has Eth0. The Snapshot Preview server OS will see the new MAC address and the Ethernet adapter name will be changed to Eth1. As the Snapshot Preview server will still have the config file's for eth0, the eth1 will not come up, this causes the Virtual Machine to stay off the Network.

If this issue occurs, this issue will appear immediately when the Snapshot Preview server is booted and the NICs are connected. It should be addressed as described below as the issue will persist even after the server is migrated as described in How to Migrate a "Snapshot Preview" Server to a Normal Cloud Server unless the changes described in this article are made. Alternately, you can choose to preserve the MAC addresses of the original server when creating the Snapshot Preview server to avoid the problem as described in How to Create a Snapshot Preview Server from a Local SnapshotHowever, that option opens up the possibility of a MAC address conflict. For more details, see Introduction to Cloud Server Snapshots

Affected Operating System List:

The list below identifies operating systems known to be affected by one or both of the issues:

Operating SystemMAC Address Change issueEthernet Adapter Name Change Issue
RHEL 4YesYes
RHEL 5Yes

Yes

RHEL 6YesYes
RHEL 7YesNo
CentOS 5YesYes
CentOS 6YesYes
CentOS 7YesNo
Oracle Linux 5YesYes
Oracle Linux 6YesYes
Oracle Linux 7YesNo


How To Address The Issue

  1. Once the Server is deployed from a Snapshot, console into the newly deployed Server and Update the MAC address:

    Note: For instructions on how to gain Console access, see How to Get Virtual Console Access to a Cloud Server
    Note: Login to Console using the same credentials as the parent machine - the machine from which the Snapshot Server was created


  2. Perform [ifconfig -a] to identify the name of the ethernet and the new MAC Address:

    Note: In this example, Ethernet is: eth1 and the MAC Address is: 00:50:56:A3:5E:A7

  3. Navigate to network scripts by using [ # cd /etc/sysconfig/network-scripts]:


  4. Open the ethernet configuration file using vi editor (In this example, my config file is ifcfg -eth0) and replace the HWADDR with the new MAC address:

    Note: To Edit the config file, Press " I " to Insert/Edit and once you finish the Edit Press " :wq " to save and exit.

  5. As soon as you save and exit, bring the interface up by using the [ifup] command. Once the Interface is up, the server will be online:

    Note: This step is applicable only if the Ethernet Adapter name has NOT Changed. If your ethernet adapter name has changed, proceed to NEXT Step.

  6.  If your Virtual Machines ethernet name has changed, Navigate to udev rules by using the following command: 

    cd /etc/udev/rules.d


  7. Once you are in the udev folder, remove the 70-persistent-net.rules file, and reboot the machine. This process will rename the ethernet adapter to original (Parent):

    rm -rf 70-persistent-net.rules