DYNAMIC COMPOSITION OF AN EXECUTION ENVIRONMENT FROM MULTIPLE IMMUTABLE FILE SYSTEM IMAGES

• US 20090216811A1
• Filed: 02/21/2008
• Published: 08/27/2009
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Vick, Christopher A., Paleczny, Michael H., Manczak, Olaf
• Granted Patent: US 7,805,409 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/188 Virtual file systems

Abstract

A virtual file system is formed configured to enable the dynamic composition of immutable file system images. A file system containing a software distribution is divided into a plurality of mutually exclusive sub-trees. Each sub-tree includes a portion of the software distribution. An immutable file system image is formed for each sub-tree. During the booting of an operating system, a virtualization engine intercedes in the boot process to mount the immutable file system images to independent directories of the root file system. Upon request the virtualization engine, during run-time, combines virtual entries corresponding to immutable file system images so as to resemble the original software distribution.

Claims

1. A system for the execution of immutable file system images, the system comprising:

a file system tree including a plurality of mutually exclusive sub-trees, each sub-tree comprising individual software components of a software distribution.

a plurality of immutable file system images wherein a separate immutable file system image corresponds to each of the plurality of mutually exclusive sub-trees and wherein each separate immutable file system image includes a file system structure; and

a virtual file system associated with the plurality of immutable file system images, wherein at run-time the virtual file system interposes the file system structure of each separate immutable file system image dynamically forming the software distribution based on the plurality of immutable file system images.

2. The system of claim 1 wherein each of the plurality of immutable file system images are read-only files.

3. The system of claim 1 further comprising a virtualization engine wherein the virtualization engine includes a rule module configured to create rules regarding immutable file system access instructions.

4. The system of claim 3 wherein a kernel forms a root file system and wherein the virtualization engine substantially establishes the virtual file system simultaneous to establishment of the root file system.

5. A method for the execution of immutable file system images on a computer system, the method comprising:

establishing a root file system;

forming a plurality of immutable file system images wherein each of the plurality of immutable file system images is associated with a mutually exclusive sub-tree of a file system tree;

attaching each of a plurality of immutable file system images to an independent directory of the root file system prior to attaching other file systems to the root file system;

generating a virtualization data structure corresponding to an empty file system tree;

creating at run-time, in the virtualization data structure, a virtual directory including a virtual entry for each of the plurality of immutable file system images wherein each virtual entry includes file system structure of the mutually exclusive sub-tree; and

joining functionally at run-time two or more of the plurality of immutable file system images by combining the virtual entries for each of the two or more of the plurality of immutable file system images.

6. The method of claim 5 wherein root file system establishment is halted prior to mounting of any existing file systems.

7. The method of claim 5 further comprising examining each of the plurality of immutable file system images to identify a mutual directory common to two or more of the plurality of immutable file system images wherein the mutual directory includes a separate entry from each of the two or more of the plurality of immutable file system images.

8. The method of claim 5 wherein authenticity of each of the plurality of immutable file system images can be verified prior to attaching.

9. The method of claim 5 further comprising writing to a memory an actual location identifier for each virtual entry of the virtual directory.

10. The method of claim 9 wherein the actual location identifier for each virtual entry of the virtual directory can be replaced while the computer system is running.

11. The method of claim 10 wherein the virtualization data structure is accessible via a virtual file system (“

VFS”

) application programming interface (“

API”

) and wherein the VFS API determines entry locations using the actual location identifier.

12. The method of claim 9 further comprising regenerating the virtualization data structure when a valid attempt to modify at least one of the separate entries in the virtual directory is received.

13. The method of claim 5 wherein the file system tree includes a software distribution.

14. The method of claim 13 wherein combining the virtual entries of the two or more of the plurality of immutable file system images functionally recreates the software distribution.

15. A virtual file system tree for dynamic composition of a plurality of read-only file system images containing software in pre-installed form operable in a machine capable of executing instructions embodied as software, the system comprising:

an operating system having an initial root file system tree; and

a plurality of software portions, wherein

one of said software portions is configured to mount each of the plurality of read-only file system images under an independent directory of the initial root file system;

one of said software portions is configured to create a virtual file system tree separate from the initial root file system tree;

one of said software portions is configured to form as part of the virtual file system tree a mutual directory wherein the mutual directory includes a virtual file having a path to each of the plurality of read-only file system images; and

one of said software portions configured to replace at least one of the virtual files while the operating system is running.

16. The system of claim 15 wherein, responsive to replacing the initial root file system with the virtual file system tree, mounting additional read-write file system trees to the virtual file system tree.

17. The system of claim 15 wherein one of said software portions is configured to form a read-only file system image by combining a plurality of virtual files.