# Error switching from Knots pre-RDTS to Knots Blake2b

**URL:** <https://community.start9.com/t/error-switching-from-knots-pre-rdts-to-knots-blake2b/5717>\
**Category:** DIY Community\
**Created:** [September 8, 2026, 1:37pm UTC](https://community.start9.com/t/error-switching-from-knots-pre-rdts-to-knots-blake2b/5717 "2026-09-08T13:37:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![matt996](https://community.start9.com/letter_avatar_proxy/v4/letter/m/7ab992/32.png) [@matt996](https://community.start9.com/u/matt996)\
**Post date:** [September 8, 2026, 1:37pm UTC](https://community.start9.com/t/error-switching-from-knots-pre-rdts-to-knots-blake2b/5717/1 "2026-09-08T13:37:24Z")

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Running StartOS 0.4.0.1. I’m attempting to switch to Knots 29.4.1:7 (custom registry start9.mempool.guide), from currently installed and working Knots pre-RDTS 29.3:26 (community registry). After downloading the update the OS gives the following error message, and the service remains at pre-RDTS 29.3:26.

> Unknown Error: Error: uninit target range `!` is unsatisfiable - no version can satisfy it (host contract violation)

Appreciate any guidance.

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<div class="post-metadata">

**Author:** ![matt996](https://community.start9.com/letter_avatar_proxy/v4/letter/m/7ab992/32.png) [@matt996](https://community.start9.com/u/matt996)\
**Post date:** [September 8, 2026, 2:27pm UTC](https://community.start9.com/t/error-switching-from-knots-pre-rdts-to-knots-blake2b/5717/2 "2026-09-08T14:27:32Z")

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Update - attempted selecting the previous version, Knots 29.4.1:6 and it went ahead and installed without issue. Now it is going through the chain rewind and re-sync to the blake2b chain, but crucially without doing a full IBD. I will let it sync up and then attempt the update to Knots 29.4.1:7.