Zabbix Agent 2 5.0 - all plugin based stuff is inside the config file.

Zabbix Agent 2 6.0 - plugin configuration can be put in separate files in conf.d/ folder using include option

In 6.0 the default parameter for this is set to this relative path:

Include=./zabbix_agent2.d/plugins.d/*.conf

Under Include parameter definition, there are only absolute paths specified as valid ones:

# Include=
# Include=/usr/local/etc/zabbix_agent2.userparams.conf
# Include=/usr/local/etc/zabbix_agent2.conf.d/
# Include=/usr/local/etc/zabbix_agent2.conf.d/*.conf

The problem here is if you use the agent configuration file with Zabbix Sender.

You run sender command from lets say home directory like this:

zabbix_sender --config /etc/zabbix/zabbix_agent2.conf --key testkey --value testvalue

And then you will get this error:

zabbix_sender [1751532]: ./zabbix_agent2.d/plugins.d: [2] No such file or directory

This happens because zabbix_sender does not know this relative path.

I would propose moving the relative directory to an absolute one:

Include=/etc/zabbbix//zabbix_agent2.d/plugins.d/*.conf