Flushing Caches Best Practices

[cmeyer]

Hello,

I have a topic regarding Casper maintenance options and could use the community’s assistance.

Recently at Extensis we’ve encountered customers who have chosen to run the “Flush (User and System) Caches” on their machines at startup but are not forcing the systems to restart after the process. This Casper maintenance task is clearly causing instability in the OS and causing all sorts of font related issues.

Not having a Casper installation at Extensis we had to play detective and rely on our review of Universal Type Client logs against the customer’s Casper logs to realize the cache flushing was causing their system instability.

Normally (as a best practice) I would expect that the OS would be restarted after this type of maintenance task but I’m not really sure what the best practice should be since Casper allows cache flushing without a system reboot.

So my questions are as follows:
- Does anyone run the Flushing Caches option in their environment?
- If so should caches be flushed on a regular basis and how often?
- Is employing a scripted OS restart the best practice or should the Casper product enforce this automatically when system caches are deleted during startup?

Thanks in advance for your feedback.

Cheers,

Chris Meyer
Sr. Product Manager, Font Management Solutions
2012 Celartem, Inc. dba Extensis. All rights reserved.

[donmontalvo]

We really wouldn't recommend flushing font caches without an immediate reboot. While kickstarting the daemon is possible, you lose your font registration state. See man atsutil:

https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man8/atsutil.8.ht...

server queries the status of fontd or shutdowns the fontd. Shutting down the fontd will spawn a new fontd. Shutting down the server is NOT recommended and will likely lead to misrendered text or application crashes.

...and...

server [-ping | -shutdown] -ping query running fontd. -shutdown shutdown fontd and spawn a new fontd. NOTE: this action is not recommended. See above.

...and the thread below.

https://www.jamf.com/jamf-nation/discussions/5677/jnuc-maintain-your-sanity-with-self-service

We provide font cache clearing through Self Service for groups that request it, but the user is warned to close all applications and expect an immediate reboot. Flushing font caches isn't something that's done often, but when it is...bounce the box. ;)

Don

[cmeyer]

Thanks Don, it has been our experience that customers who do not restart their systems after flushing OS caches saw system instability until they performed a system reboot. Your validation is appreciated.

[mike_paul]

Hello All, I just wanted to check in here to see if you are still leveraging the use of Flushing User and/or System Caches on more modern operating systems? We're currently evaluating the usefulness of these functionalities and your feedback would help up us.

Thanks
Mike Paul
Jamf Pro Product Manager

[donmontalvo]

@mike.paul wow didn't notice your post until just now, when I was searching for something unrelated.

We still see cases where a user's font caches can get corrupt, flushing and rebooting user and computer domains fixes the problem.

Whether the computer domain is needed anymore, not sure, since we combined both into a single policy.

Might be a question for Apple.

[gabester]

@mike.paul Likewise, Mike echoing @donmontalvo we do use this rarely, but when we need it it's certainly nice to have. It would be great if the featureset could be updated for 2020-era relevance, although I cannot succinctly state what I think that might be (collecting logs for analysis, "reset user to clean profile", that sort of thing which we currently end up doing as bespoke scripts.)