# Recalculate Checksum after safety setting change without Teach Pendant installed

**URL:** <https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430>\
**Category:** Technical Questions\
**Tags:** teach-pendant, safety-system, checksum\
**Created:** [December 18, 2017, 7:40pm UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430 "2017-12-18T19:40:19Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![anon30558613](https://avatars.discourse-cdn.com/v4/letter/a/858c86/32.png) [@anon30558613](https://forum.universal-robots.com/u/anon30558613)\
**Post date:** [December 18, 2017, 7:40pm UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430/1 "2017-12-18T19:40:19Z")

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My company is trying to run a UR robot headless (i.e. without a Teach Pendant). One of the impediments we are facing is changing the safety parameters on the robot without the Teach Pendant.

Does anyone know how the safety checksum is generated for both the safety.conf and urcontrol.conf files? It mentions in the header at the top of the file that there is a supplied tool; however, I have not been able to find this tool anywhere on UR’s website.

Would it be possible to share this tool?

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**Author:** ![mmi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/mmi/32/691_2.png) [@mmi](https://forum.universal-robots.com/u/mmi)\
**Post date:** [January 12, 2018, 2:35pm UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430/2 "2018-01-12T14:35:11Z")

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Hi Josh,  
Tool is actually built into polyscope. It’s not super easy to use, but basic steps are as following (assuming you’re trying this on virtual machine with simulator 3.5.x):

- Create base installation with polyscope, save as default.installation
- Open terminal
- Go to programs directory
- Change installation name to default.installation.gz, and use gunzip to extract raw ascii installation file
- Change values in installation file (no need to compress it afterwards)
- run  
`java -classpath $(echo ~/ursim-current/GUI/bundle/*.jar | tr ' ' ':') -Djava.library.path=/root/GUI/lib com.ur.safety.SafetyCRCUpdater default.installation`  
to recalculate checksum, and update installation file

At this point you can load installation through polyscope dashboard server.

> NOTE: keep in mind that this interface is for development and testing purposes, and UR does not guarantee that it will stay in the same place, or even be available for future releases.

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**Author:** ![anon61872178](https://avatars.discourse-cdn.com/v4/letter/a/a87d85/32.png) [@anon61872178](https://forum.universal-robots.com/u/anon61872178)\
**Post date:** [April 26, 2018, 9:55pm UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430/3 "2018-04-26T21:55:59Z")

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Hi mmi@,

I followed your instructions and edited `min|maxJointPosition` and `min|maxJointRevolutions`. For some reason when I run the java command `java -classpath $(echo /opt/ursim/GUI/bundle/*.jar | tr ' ' ':') com.ur.safety.SafetyCRCUpdater /opt/ursim/programs.UR10/default.installation"` all my changes got “reverted”, i.e. joint limits where back to defaults. Any idea why this is happening?

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**Author:** ![liyunbao123](https://avatars.discourse-cdn.com/v4/letter/l/2bfe46/32.png) [@liyunbao123](https://forum.universal-robots.com/u/liyunbao123)\
**Post date:** [January 4, 2021, 3:51am UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430/4 "2021-01-04T03:51:46Z")

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Hi mmi,

when i run the command, the result said that could not find or load main class com.ur.safety.SafetyCRCUpdater. And I test all the file in the GUI, but also not found the class.

Could you tell me how to resolve the question ？

Thank you very much!

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**Author:** ![mmi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.universal-robots.com/mmi/32/691_2.png) [@mmi](https://forum.universal-robots.com/u/mmi)\
**Post date:** [January 13, 2021, 2:06pm UTC](https://forum.universal-robots.com/t/recalculate-checksum-after-safety-setting-change-without-teach-pendant-installed/1430/5 "2021-01-13T14:06:59Z")

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I had troubles running that tool - polyscope got much complicated over last years.  
I’ll try to find a way to run this tool.