zabbix_agentd.conf has default include:

Include=/etc/zabbix/zabbix_agentd.conf.d/*.conf

I have file vfs.fs.ro.conf in zabbix_agentd.conf.d with one line:

UserParameter=vfs.fs.ro[*],if [ -z `touch $1/zabbix_filesystem_check 2>&1 | grep "Read-only"` ]; then echo 0; else echo 1; fi && [ -e $1/zabbix_filesystem_check ] && rm $1/zabbix_filesystem_check;

Zabbix agent fails to start with:

"ERROR: cannot add user parameter"

When I rename vfs.fs.ro.conf to vfs.fs.ro or vfs.fs.ro.conf.bak or any other name, zabbix agent starts and correctly reads this file, I check this with:

zabbix_get -s server -k vfs.fs.ro