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Whilst auditing disk space on our Windows 2008R2 farm we noticed that some servers had quite large C:\Windows\Logs\CBS\CBS.log files (~1.5GB).

I was under the impression that this particular log file would be periodically compressed into CbsPersist_yyyymmddtttttt.cab (where y,m,d,t are year, month day and time respectively) files to reduce space used.

Can I safely delete these large CBS.log files?

If my understanding about CBS.log being periodically compressed is correct, why isn't this happening on my servers?

Kev
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2 Answers2

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By stopping the "windows module installer" you can safely delete the file, and yes the cab files should be being created, this can happen on Windows 2008R2 when the CBS.log file grows too fast for the compressor to notice (yes, not the greatest way of doing things) or if there is a error during compression. Check the event logs for why this might not be happening.

mubix
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  • That service is not stoppable for me (Windows 7). – Jannes Sep 18 '15 at 13:56
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    I manually killed the TrustedInstaller.exe process and then deleted all files in the CBS directory. Seems to have worked. – Jannes Sep 18 '15 at 14:02
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    One particular error during compression is file size. If the log gets above 2 GB, the tool to compress to CAB will throw an error (since apparently CAB doesn't support greater than 2 GB). Wish they would drop CAB and go for zip (or even better, 7z). – jpmc26 Feb 13 '16 at 05:14
  • see also http://felixyon.blogspot.be/2013/03/mysterious-cab-files-fill-up-temp-folder.html – juFo Nov 10 '16 at 08:22
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Be sure you have the latest Windows update agent:

https://support.microsoft.com/en-us/kb/949104

Delete everything in the C:\Windows\Temp folder; you may not be able to delete a few files, that's ok. I've also deleted all but the current month of CbsPersist_.log and CbsPersist_.cab files in the C:\Windows\Logs\CBS folder without issue.

E-Man
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