[SOLVED] Component-Based Servicing (cbs.log) causes all drive space to be consumed

Question

Because I've seen this question asked in many places and not answered, I thought I'd post my issue and resolution here.  I regard this as a Bug, but I'm not invested enough to deal with the support incident process.

I've had repeated instances where a Windows 7 x64 client runs out of hard drive space, and found that C:\Windows\TEMP is being consumed with hundreds of files with names following the pattern "cab_XXXX_X", generally 100 MB each, and these files are constantly generated until the system runs out of space.  Upon removing the files & rebooting, the files start being generated again.

I've found that this is caused by large Component-Based Servicing logs.  These are stored at C:\Windows\Logs\CBS.  The current log file is named "cbs.log".  When "cbs.log" reaches a certain size, a cleanup process renames the log to "CbsPersist_YYYYMMDDHHMMSS.log" and then attempts to compress it into a .cab file.

However, when the cbs.log reaches a size of 2 GB before that cleanup process compresses it, the file is to large to be handled by the makecab.exe utility.  The log file is renamed to CbsPersist_date_time.log, but when the makecab process attempts to compress it the process fails (but only after consuming some 100 MB under \Windows\Temp).  After this, the cleanup process runs repeatedly (approx every 20 minutes in my experience).  The process fails every time, and also consumes a new ~ 100 MB in \Windows\Temp before dying.  This is repeated until the system runs out of drive space.

This can be reproduced by trying to manually create the cab file -

 Directory of C:\CBS-BAK

08/26/2015  02:28 PM    <DIR>          .

08/26/2015  02:28 PM    <DIR>          ..

08/22/2015  09:12 PM     2,491,665,966 CbsPersist_20150823021618.log

C:\CBS-BAK>makecab CbsPersist_20150823021618.log

Cabinet Maker - Lossless Data Compression Tool

 86.19% - CbsPersist_20150823021618.log (1 of 1)

ERROR: (FCIAddFile)Data-size or file-count exceeded CAB format limits

C:\CBS-BAK>dir %TEMP%\cab*

 Volume in drive C is OSDisk

 Volume Serial Number is 44DE-0CDD

 Directory of C:\Users\USERNAME\AppData\Local\Temp

08/26/2015  02:31 PM       102,786,654 cab_4556_2

08/26/2015  02:28 PM                 0 cab_4556_3

08/26/2015  02:28 PM                 0 cab_4556_4

08/26/2015  02:28 PM                 0 cab_4556_5

08/26/2015  02:28 PM                 0 cab_4556_6

08/26/2015  02:28 PM        12,978,919 cab_5860_2

08/26/2015  02:27 PM                 0 cab_5860_3

08/26/2015  02:27 PM                 0 cab_5860_4

08/26/2015  02:27 PM                 0 cab_5860_5

08/26/2015  02:27 PM                 0 cab_5860_6

To resolve this -

Stop the Windows Modules Installer (TrustedInstaller) service

Delete or move the large Cbspersist_XX.log file out of \Windows\Logs\CBS.

Start the Windows Modules Installer (TrustedInstaller) service

Answer 1

It is most likely the failed 1709 update issue. Check out my earlier post on December 19th with the link to the instructions to get the update to complete. The cbs.log will then be reset and start working correctly again.

Answer 2

If you open up Services.mcs, it's listed under Windows Modules Installer(unless you've already done that). Right click it, click properties, then set 'Startup type' to Manual or Disabled. Disabled should end it immediately, whereas, with manual it should stay running and other services like updates and installing apps *seems* to start it up without the user doing so. I set it to disabled because it takes up 50% of my CPU usage. I have the same issue with the log files taking up space but it only happens when I shutdown or startup Windows, which leaves Windows on the 'Getting Windows Ready' screen for an hour or so and leaves me 100 - 200 GB worth of logs. I don't know if you would want to leave it disabled, though, in case some process like updates might need it.

Answer 3

I took delivery of a new Windows 10 computer to run our CT scanner with a 1TB SSD less that a week ago.  Today, we got an alert that we were out of disk space (0 bytes free).  I was stunned by this, as there was only a handful of executables on the computer.

I cleared off some disk space, then watched the free space drop by gigabytes at a time while doing literally nothing.

I thought it might be a virus, so I did  a scan...nothing.

Then I did a search for large files:

There are five cbspersist.log files, the smallest was 50GB, and the largest was 335GB.

I am astonished at the level of destruction, and how long this problem has been known, and that there is no warning, and that could bring a critical piece of equipment to a standstill.

https://www.computerworld.com/article/3112358/microsoft-windows/windows-7-log-file-compression-bug-can-fill-up-your-hard-drive.html

It just consumed hard disk space to the point of failure with absolutely no warning.

Check your C:\Windows\Logs\CBS for CBSPerist.log(s).

Answer 4

It is most likely the failed 1709 update issue. The huge cbs.log and cbspersist.log is just a symptom of the failed Windows update. You can remove the logs, but they will return once you try to update again. I found the answer to get the Win 10 1709 update completed and the CBS.log to return to normal use here:

https://answers.microsoft.com/en-us/windows/forum/windows\_10-update/dec-2017-update-fail-windows-10-stuck-for-hours/a7220564-562e-4a83-98fe-2b1bdf4f08f2

Answer 5

I just wanted to put my info out there. Noticed all my disk space was gone and used Treesizefree to locate the CBS.log devouring my space.... my precious... limited SSD space...... 

Experienced the same issue as many here. CBS log file well over 200 gigs, shut downs taking hours or more - all after this last updated. I did want to mention I have a Samsung Evo 850 and 840. I noticed another reply mentioned this but not sure if its related in any way. 

For now I have stopped the Windows Module Installer service from running. I have had to clear the CBS.log file three times in the last week as it keeps growing and eating all the precious space I had left.