As Wechsler notes, WES and XPe are binary-compatible with Windows XP Professional, for which Microsoft regularly rolls out security and application fixes on "Patch Tuesdays." As a result, he writes, an "overeager administrator could therefore have the idea of installing all of those patches as they come in, just to be on the safe side."
But, he adds, "what is good in the enterprise may not be good for embedded devices." In fact, WES and XPe deliberately omit the Windows Update feature that's found on desktop editions of XP, according to the author.
Reasons it may not be good to update embedded operating systems too frequently include the following, as explained by Wechsler:
- Embedded devices offer only a subset of desktop functionality -- for example, they may not include Media Player and Internet Explorer -- and you cannot patch what is not there
- Storage on embedded devices is limited, and unnecessary patching would increase the image size
- If a system is running well and the patch is adding functionality that is not directly in line with the device's primary use, one should think twice before updating it
In his posting, Wechsler also explains that there are two basic ways to update an embedded operating system.
Partial updates constitute patches to applications, drivers, or other components in an already running OS image.
Complete updates, also known as image refreshes, constitute a complete replacement of an operating system image.
Wechsler says partial updates, often used for security fixes, are bandwidth-friendly and therefore much faster to deploy. However, he adds, they can impose higher development costs, associated with testing and with creating and managing multiple OS versions.
Complete updates, on the other hand, are said to make more sense for delivering larger patches such as service packs, where the size of the patch approaches the size of the whole OS image in any case. However, adds the author, once patches have been applied to the WES database, the problem of getting new images out into the field still exists.
"It is impossible for anybody to foresee all the changes that may be needed to a device after it has been rolled out," Wechsler notes. Therefore, developers and administrators should set up their infrastructure for both partial and complete updates, preparing their WES images and back-end systems accordingly, he says.
Alexander Wechsler was formerly an embedded partner manager for Microsoft, according to his
MVP Profile on the Microsoft website. He later left to found his own company,
Wechsler Consulting, but is a regular participant in Microsoft's online chats and other activities.
Further informationWechlser promises future blog posts on this important topic, looking further at change management scenarios and at the required software tools. To read his first posting on Windows Embedded change management, see the Windows Embedded blog,
here.
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