A working Ceilometer installation will have several processes running, some of which are as follows:

When troubleshooting Ceilometer, an effective place to start is ensuring that each of the preceding processes run. As we've seen before, we can verify this by running either ps -aux or pgrep on Ceilometer. Take the following command, for example:

Alternatively, you can use the pgrep command to retrieve similar information. An example is included in the following screenshot:

If any of these processes are not running as expected, you can search the log files for possible clues. The log files for Ceilometer are typically stored at /var/log/ceilometer, but you can confirm the log file location by checking the Ceilometer configuration file for the value of the log_dir variable. If the log files are empty or do not provide any clues, you can attempt to start the services manually, which will cause the output to be printed to the console as the process starts up. For example, to start ceilometer-api manually, you would use a command similar to the following:

sudo -u ceilometer ceilometer-api --config-file=/etc/ceilometer/ceilometer.conf --log-file=/var/log/ceilometer/ceilometer-api.log

If there are errors during startup, examine the output carefully for clues pointing to the root cause.