When Elastic Layering is enabled (with or without User Layers), the boot disk is created with an extra 20GB as a second partition where the user writes will be stored. 

This is necessary to keep writes at a layer above the boot disk and any elastically assigned layers that might show up later.

If you need to adjust the volume size, you can either manually edit the disk after publishing to expand it, and then expand the second partition, or you can change the writable partition size for all published images.

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Instructions

For App Laying 2106 and higher:

When creating or editing an Image Template, you can now set the writable partition size from the image template wizard.

From the App Layering console please create or edit a template:

Images -> Create / Edit Template -> Layered Image Disk -> Writable Partition Size.





Manual Instructions for versions prior to App Layering 2106:

Should they want to use a different size they would change the Application Setting on the ELM to specify the different size.

NOTE 1: The changes will not be in effect until a service is restarted. Restart should be done when there are no tasks in a running state.

NOTE 2: This will not work when Offload Compositing is enabled in the connector. As needed use a connector with Offload disabled to publish images and another, with Offload enabled, for packaging tasks. This is no longer a limitation in App Layering 2106 and higher when using the image template wizard. However this still applies for the manual steps below.
 

1. Make a snapshot of the Enterprise Layer manager (ELM) in your hypervisor to allow you to recover if you make a mistake (delete it only after you've tested the change)
2. Connect to the ELM (Linux appliance) via console and log in as root
3. Change directory to  /usr/local/CAMService
4. Edit CAMService.exe.config using the built-in text editor: nano, EMACS and vi are all native to CentOS.
5. Navigate to the appSettings section of the config file.
6. Add a new line with the text: <add key="ScratchVolumeSizeInMB" value="20480"/>
7. Change the 20480, which is 20 GB to the value you want to use.
8. Write, save the changes to the file, and close it
9. Wait until no tasks are in progress, Then restart the ELM, or restart the service, CAMService, with the following commands:
   1. service cams stop
   2. service cams start
10. Publish a new image and verify

Keep in mind that the value is in MB so remember to multiply your number by 1024 to get the proper size (20 * 1024 = 20480).
 

How to set the default size of the Elastic Layering writable volume