Patent Application
20050044548
1. Field of the Invention
The present invention is directed to the field of cloning operating systems, and more specifically, to the field of imaging or replicating embedded operating systems that include an overlay or write filter partition.
2. Description of the Related Art
An operating system manages and makes available the resources of a computer. Some operating systems, such as Windows XP, have an embedded version with special features to improve reliability, mass deployment, ease of administration, etc. For example, because an embedded operating system may be intended to run on a minimal hardware platform, one feature is that unnecessary operating system components may be omitted to reduce its production size. Also, because embedded operating systems are sometimes used on computers that require reliable low-maintenance operation, the embedded system may be protected or kept in its originally configured state by storing it on a read-only partition or storage medium.
For flexibility, an overlay is sometimes provided or configured to keep changes to the embedded system separate from the original installation of the system; the original installation stays constant. This makes it possible to easily restore or reset the system if it becomes corrupt. Any corruption will be on the overlay, and the overlay can be deleted or flushed to reset the system to its original state.
More detailed discussion of an embedded operating system and an overlay for the same may be found in “Windows XP Embedded Step by Step”, by, James Beau Cseri, published by RTC Books in March 2003 (ISBN 0929392736), which is incorporated herein by reference.
System imaging is a known process for reproducing, often en masse, a master computer system such as a production-configured embedded operating system. An image of a preconfigured master system is created. The image is then used as a source to clone the master system. Clones of the master system are created and initially mirror the master system. It is often necessary or desirable to create a master image of an embedded system that includes an overlay, or where an overlay is desired in the clones created with the image. However this has not been previously possible using standard imaging tools. What is needed is a method of efficiently imaging a system with an overlay, which typically comprises a write filter and an overlay partition.
It is an aspect of the present invention to provide a method of imaging an embedded system that does not require manual creation of a writable overlay.
It is another aspect of the present invention to provide a method of automatically creating an image of a master embedded system where a clone of the image automatically creates its own overlay partition.
It is yet another aspect of the present invention to provide a method or system that may be used to clone a master system using imaging tools, where clones of the master system self-create overlays when booted.
It is still another aspect of the present invention to provide a method for imaging a system with a write filter that does not require bit-by-bit copying of a complete hard disk found in the system being imaged
It is another aspect of the present invention to provide a compressed system image that is decompressed with an imaging tool and that is enabled to self-create a write filter and overlay partition when booted.
It is a further aspect of the present invention to produce system images enabled for overlays that are not limited to being installed on a given disk size or configuration.
The above aspects can be attained by a system or process for cloning a master embedded system configured with a non-writable volume or partition that stores an embedded operating system, where the master system is configured to provide an overlay to store updates directed to the non-writable volume or partition. A flag in the master system is configured with a setting, where the configured flag is for indicating that the overlay is needed and has not been provided. After configuring the flag, a master image of the master system is created, preferably with a compressing imaging tool, where the master image includes the configured flag. A clone of the master system is created on a storage of another system based on the master image. Storage units may store images created with the process. Storage units may also store cloned systems produced with the images. A clone of the master system may be provided with an overlay based on the setting of the flag in the clone of the master system, where the overlay provides file-system level write functionality to the non-writable volume or partition of the clone system.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.
As mentioned in the Background, when manufacturing computer systems (e.g. duplicating an embedded system), it is known to create a single image of the operating system and replicate it onto the hard drives or storage units of multiple and often identical computers. System imaging saves time and prevents errors that would occur with multiple individual installations. Two previous approaches to system imaging were to exactly copy, bit-for-bit, the master system, or to use an imaging tool to create a compressed or condensed image. However, with the first approach, the created image can only be installed onto a hard drive with the same size and configuration of the master's hard drive. Furthermore, images created with the bit-by-bit imaging approach are large and take a long time to create. Their size can make them impractical for network-based image installs.
The second approach of using an imaging tool is preferable to the bit-by-bit approach because imaging tools create a compressed or condensed image, which may be installed in much less time than a bit-for-bit mirror image and which may be installed on any size or configuration of hard drive. For example, an imaging tool might ignore free disk space in a master partition. When installing from the image, the imaging tool explodes the condensed image to the destination clone system. PowerQuest DriveImage and Paragon Drive Backup are examples of tools that may be used to clone or image a master or source system. Imaging tools have not been feasible when an overlay is needed in the clone systems. These kinds of tools typically scan the disk drive of the master system to look for partitions of standard types, such as the NT File System (NTFS) partition type or the File Allocation Table (FAT) partition type. These imaging tools typically compress those partitions into a small image package, for example a ZIP file. There may also be logical compression that identifies and omits unnecessary components. Such compressed images are usually conveniently stored on a network where clones based on the image are being produced. Such an image may then be used to produce clones of the master system.
There is a problem with image cloning tools. Cloning tools are not able to recognize non-standard types of partitions. Cloning tools tend to ignore non-standard types of partitions and do not include them in the produced compressed image. Windows XP Embedded (XPE), for example, uses a non-standard partition type for the overlay partition that stores filtered data. Thus, when the write filter is included as part of the operating system it cannot be accurately replicated to multiple hard drives using software imaging tools. Only the bit-by-bit copy has been able to duplicate an overlay partition, but has the limitations discussed above.
It is noted that there has been a need in the field of high volume system production to create a condensed image of Windows XPE having an overlay by using standard imaging tools. Many system administrators have been frustrated in their attempts, and despite significant effort, no satisfactory workarounds have been previously discovered. Other attempts, usually manual, have fallen short in the result and have not achieved mass duplication. Even a concerted effort on the part of the Microsoft Corporation failed to find any solution and recommended the unacceptable approach of using bit-by-bit copying. An aspect of the present invention allows existing standard imaging tools (or future imaging tools) to be used to replicate an operating system such as Windows XPE when it has a write filter and overlay partition while preserving all of the advantages of tool-based system replication. The technique discussed below, although simple in practice, is highly reliable and efficient, and does not significantly increase the size of the produced image.
After these steps, any additional configuration or software that is to be part of the embedded system is installed 80. Then, a flag used for indicating whether the write filter has been initialized is set 82 to zero (e.g. false). Setting 82 the flag essentially tells or indicates to the system: “the write filter partition for this system has not been created”. For example, in Windows XPE, the flag or registry subkey has typically been “HKEY_Local_Machine\System\CurrentControlSet\Control\WindowsEmbedded\FBA\42939191 XX”, where XX varies (FBA stands for First Boot Agent). This subkey contains an “FBAWasHere” flag or value. Although the registry is subject to change with new operating system releases, the correct registry entry can be recognized by its Parameters key, which references “ewfdll.dll”. After setting 82 the “FBAWasHere” flag to zero, the system is resealed 84, for example by running “fbreseal.exe”. At this point, the master image is enabled to self-create the write filter and partition. Because that flag has been set 82 to zero, the operating system will, on the first boot after resealing 84, consider the flag and understand that the write filter and its overlay partition require initialization and creation. Standard tools may be used 84 to replicate and deploy the image. Finally, the master system may be imaged and/or deployed 86 using standard imaging tools.
Resealing 84 is a process by which a system is logically reset, at least partially, to a state of not having been booted. Resealing sets a reseal flag in the system that indicates that the system has been resealed and causes the system when booted to go through several first-boot items, discussed below. Resealing 84 the master system naturally causes the clones or copies of the master system to also be in a resealed state. The resealing 84 allows a clone of a master image to initialize some system parameters with settings different than the master image. Typically, registry entries are set. Resealing 84 typically is used to cause the clone system to set its own unique System ID (SID), network parameters, etc. when the clone machine is first-booted. More specifically, with Windows XPE, when the master image (and therefore its unbooted clone copy) has been resealed, the operating system is enabled to recognize that it needs to run a small abbreviated First Boot Agent (FBA) when the system first boots after the resealing 84. Among other things, the abbreviated FBA checks the “FBAWasHere” flag. When it sees that the flag or registry entry is zero, it causes the write filter to become active and it causes the overlay partition to be formatted. Thus, it may be said that the master image (or clones thereof), produced as discussed above, and before having been first-booted (or before having been booted after being resealed), is enabled to or configured to self-create the overlay.
The present invention has been described with respect to a system or process for cloning a master embedded system configured with a non-writable volume or partition that stores an embedded operating system, where the master system is configured to provide an overlay to store updates directed to the non-writable volume or partition. A flag in the master system is configured with a setting, where the configured flag is for indicating that the overlay is needed and has not been provided. After configuring the flag, a master image of the master system is created, preferably with a compressing imaging tool, where the master image includes the configured flag. A clone of the master system is created on a storage of another system based on the master image. Storage units may store images created with the process. Storage units may also store cloned systems produced with the images. A clone of the master system may be provided with an overlay based on the setting of the flag in the clone of the master system, where the overlay provides file-system level write functionality to the non-writable volume or partition of the clone system.
In the embodiment discussed above, the code or software that creates the overlay partition is provided as a part of the embedded operating system. The overlay code creates the overlay partition based on the write filter registry flag during the first boot. However, it is also possible that the operating system code may be supplanted by custom written code included with the master image. The custom code can be written to format or create the overlay. In this case, the creation of the overlay could be flagged or driven by its non-existence during booting.
The many features and advantages of the invention are apparent from the detailed specification and, thus, it is intended by the appended claims to cover all such features and advantages of the invention that fall within the true spirit and scope of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.
