Resolve errors after building a server from a saved image

This article shows you how to resolve errors that might occur when you build a server from a saved image. Most of these errors occur when startup scripts are not properly configured.

The services that cause these errors are xe-linux-distribution and nova-agent. The article does not discuss these services in detail, but does show you how you how to configure these services on startup.

Because these errors are more prominent on Debian®-based servers, the example troubleshoots an Ubuntu® 13.10 server. The instructions also work on most other Linux® distributions.

Use the following steps to troubleshoot errors that occur after you build a server from a saved image:

1. Remove the new server that is experiencing issues and log in to the source server by using Secure Shell (SSH). The source server is where the original image was created.

2. Run the following command to display the current order of the server’s startup processes:

   ls -al /etc/rc$(runlevel | cut -d " " -f 2).d/
   

   The output is similar to the following image:

   

   Because this is a new server, nova-agent (S20nova-agent in blue in the image, or s20) is set to start immediately after xe-linux-distribution (S14xe-linux-distribution in the image, or s14). However, if you install certain applications, the installation might reorder the startup processes and place another service in between S14 and S20. If this reordering occurs, nova-agent does not start immediately after xe-linux-distribution. This reordering is what causes the error.

3. Move the run levels for these services so that they start up consecutively and are the first services in the init.d startup process. The following commands move the xe-linux-distribution to S01 and nova-agent to S02:

   cd /etc/rc$(runlevel | cut -d " " -f 2).d/
   mv S14xe-linux-distribution S01xe-linux-distribution && mv S20nova-agent S02nova-agent
   

   Depending on your run levels (which determine how the system starts), the preceding command varies. Ensure that you use the appropriate numbers that display in your output.

4. Run the ls -l command to verify that xe-linux-distribution is set to S01 and nova-agent is set to S02.

5. After you complete these steps, recreate your server image, and then create the server based on the new, saved image.