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Versions Affected : All versions prior to TrueNAS 12.0-U3


An interaction between the code which frees the unused portions of the microcode file and the rest of the system can cause boot hangs.

The kernel may hang during boot if boot-time microcode updates are configured.


Systems not configured to load microcode at boot-time are unaffected. Boot-time microcode loading is currently only supported with Intel CPUs. On systems that are configured to load microcode at boot-time, setting the “debug.ucode.release” loader tunable to 0 will prevent the microcode update file from being freed, working around the problem.


  • Upgrade to TrueNAS 12.0-U3 or later.


Further information