Frequently Asked Questions - Supersedence
Learn the answers to frequently asked questions about Supersedence in Ubuntu patching with BigFix.
What is Supersedence?
Supersedence is all about replacing an outdated Fixlet with the latest Fixlet.
Supersedence helps you update BigFix application Fixlets to their latest version by using newly released Fixlets. The superseded Fixlet replaces the outdated Fixlet containing the following details for backtracking.
x-Fixlet-Superseded field in the Fixlet states the newer
version number.
The superseded by version (newer version) is displayed in the Description tab as shown in the sample Ubuntu Fixlet screenshot.
What is a superseder?
Superseder is the latest Fixlet that is replaces or updates the outdated version.
What is a supersedee?
Supersedee is the outdated Fixlet that is replaced by the latest Fixlet.
Can I use the superseded Fixlet to deploy an application even if a latest version is available for the same application?
Yes. You can update the application to the latest version. You can also still use the superseded Fixlet to deploy the application. The Fixlet description mentions that there is an update available for the application.
Applications like Google Chrome allows you to download only the latest version available.
- Downloadable version: In such applications, the superseded Fixlets would deploy only the latest available version.
- Reason: The download link remains constant in all the Fixlets regardless of being a regular Fixlet or a superseded Fixlet.
Does the architecture of the package play a role in supersedence?
Yes. For example, the amd64 architecture Fixlet can be superseded only by another amd64 architecture Fixlet and not by any other architecture Fixlet.
How does supersedence work in Ubuntu?
Superseding Fixlets in Ubuntu work based on the package name and version number.
What are Kernel Fixlet and how does supersedence work in Ubuntu Kernel Fixlets?
Kernel Fixlets are the fixlets that have the package names preceeded by Linux-image, for example - linux-image-<version>-<flavour>.
- In a Kernel Fixlet with version X.Y.Z-W, X.Y is called as the minor
version. It is a prerequisite that the minor versions match for
the supersedence to work. That is, the minor version of superseder should match
the supersedee packages since HWE (Hardware Enablement) scenario is required for
Ubuntu kernel Fixlets.
For example, linux-image-4.4.x can only supersede another linux-image-4.4.x, linux-image-4.8.x can only supersede another linux-image-4.8.x, and so on.
- Supersedence occurs only if it is part of the same type, that is
linux-image-<version>-generic can only supersede another
linux-image-<version>-generic. This applies to those that have the extra
flavour type in its name.
For example, linux-image-extra-4.4.0-101-generic will be superseded by linux-image-extra-4.4.0-103-generic, but cannot be superseded by linux-image-4.4.0-103-generic.
All the Fixlets without any USN ID are grouped as Unspecified Fixlets in Ubuntu.
- If the superseder and supersedee package versions of an USN Fixlet and Unspecified Fixlet are similar, then the USN Fixlet has the priority. That is the USNFfixlet supersedes the Unspecified Fixlet.
- The Unspecified Fixlet never supersedes the USN Fixlet when the package version is similar in both the Fixlets.
Can an unspecified Fixlet supersede a USN Fixlet in Ubuntu?
Yes. Unspecified Fixlet can supersede a USN Fixlet in Ubuntu only when the unspecified Fixlet’s package version is higher than the USN Fixlet’s package version.
Will the same Fixlet be superseded two or more times?
No, when a Fixlet is superseded by the latest version, the Fixlet is marked as superseded:True in the seenfile of the corresponding OS code to avoid superseding the Fixlet again.
Are there any relevance changes for the superseded Fixlets?
Yes, additional relevance checks are equired for superseded Fixlet as shown below.<Relevance>(value of setting "_BESClient_Ubuntu_EnableSupersededEval" of client as integer = 1) | false</Relevance>