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Where does a Server inherit its configurations?

Introduction

When you launch a Server, there are several places where different inheritance rules apply to ensure that a Server will properly be configured.  It's important to understand where a Server will ultimately inherit certain configurations in order to properly configure your Deployments, as well as for troubleshooting purposes.

Remember, a Server is either "inactive" (yet to be launched) or "active" (a running instance in a cloud).  This document specifically addresses inactive or "Next" servers which defines how the next instance of that Server will be configured when it's launched. 

Diagram

The diagram below highlights where a Server will initially inherit most of its configurations.   Some configurations can be overwritten at the Deployment and Server levels.  See tables below for more details.

diag-server_resource_inheritance-v1.png

Cloud-assigned

The following configurations are assigned by the individual cloud providers and are not user-defined. These configurations only apply to active (running) Servers and are assigned to instances at launch time.

 

Configuration Cloud Provider
UID (e.g. AWS id) X
Private DNS name X
Public DNS name X
Private IP Address X
(Public) IP Address X

 

User-defined

The following configurations are defined by the user.   You have the flexibility to choose which cloud resources and RightScale components should be used to configure the instance.

You'll notice that a Server inherits a majority of its configurations from higher levels (e.g. ServerTemplate or Deployment).  As a best practice, you should rarely configure any settings at the Server level.   You'll find that it's much easier to manage all Servers in your Deployment if you configure your Servers to inherit their configurations from either the ServerTemplate or Deployment levels.  By effectively using the various inheritance rules to your advantage, you'll have a better way of ensuring overall consistency and repeatability across all Servers in your Deployment.

The table below shows where a Server will ultimately inherit its configuration.  Configurations that are defined at the right of the table (MultiCloud Image) take the least precendence, whereas any configurations that are defined at the Server level will automatically take the most precedence.  For example, a Server will initially inherit its machine image from the ServerTemplate's MultiCloud Image.  But, you can overwrite the seletion and choose a different machine image at the Server level.  See Understanding Inputs.

Configuration "Next" Server
Deployment
ServerTemplate
MultiCloud Image
NicknameRS X   X  
ServerTemplate X1      
SSH Key X      
Security Group(s) X      
Cloud X      
MultiCloud ImageRS     X  
Machine Image X     X
Kernel Image X     X
Ramdisk Image X     X
Instance Type X     X
Availability Zone* X X    
Elastic IP*  X2      
User Data* X      
Pricing Type* X      
Tag(s)RS  X3   X  
ScriptsRS  X4   X  
InputsRS X X X  
AlertsRS X   X  
EBS Volumes* X      
EBS Snapshots* X      
OS Distribution Repositories X   X  
Cookbooks Repositories Path     X  

 * AWS only
RS RightScale-specific term

Notes

  1. Change a Server's ServerTemplate.  You can either select a different committed revision or HEAD version (if available).  You cannot select a completely different ServerTemplate.
  2. Disassociate or associate an Elastic IP
  3. Edit Tags  (Add or Delete)
  4. At the Server level you can define which Scripts (RightScripts and/or Chef Recipes) are enabled.  For example, If you disable a boot script, that script will not be executed during the booting phase the next time that the server is launched.

 

Once a Server is launched and an instance is running in the cloud, you can still edit some of its configurations, however, those changes only apply to the Current (Running) Server and are not preserved in future launches of that Server.  To learn more about what you can and cannot edit on a Current Server, see Server Management.

See also

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Last modified
22:49, 16 May 2013

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