Problem
You may be impacted by a Cannot Create Graph error.
To visualize a graph, Checkmk uses RRD. The RRD needs, by nature, two files:
-rw-rw---- 1 mysite mysite 93 Jun 2 07:21 CPU_Utilization_Packet_CPU_2.info -rw-r--r-- 1 mysite mysite 384952 Jun 2 11:22 CPU_Utilization_Packet_CPU_2.rrd
The .rrd file stores all the data, and the .info file defines the service metrics. If one of the files is missing, you will face the message above. This message will also be displayed in the cmc.log:
OMD[mysite]:~$ tail -f var/log/cmc.log 2022-06-02 12:09:41 [4] [main] [rrd] [rrdcached at /omd/sites/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_1.rrd 2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Mgmt_CPU.rrd 2022-06-02 12:10:41 [4] [main] [rrd] [rrdcached at /omd/sites/mysite/tmp/run/rrdcached.sock] >> -1 No such file: /opt/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_0.rrd
Solution
Unfortunately, for some reason, one of the files is missing. In that case, it is the .rrd file. So to make the graphs work again, you need to stop the site, find all the .info files with a missing .rrd file, and to delete them manually:
OMD[mysite]:~$ for i in $(find ~/var/check_mk/rrd -name *.info); do test -e ${i%info}rrd || echo $i; done
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/PING.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Mgmt_CPU.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_1.info
/omd/sites/mysite/var/check_mk/rrd/<HOSTNAME>/CPU_Utilization_Packet_CPU_0.info
Now you have a list of files to delete. Please replace echo $i with rm $i in order to delete those files.
After you delete the affected files, you need to start the site so the new files are created.
Checkmk does not delete any .rrd file. So it could be deleted by a custom cleaning job!
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