inputs.diskio (via gopsutil) reads /run/udev/data/b<major>:<minor> to
get per-device tags. Without the mount it falls back to the legacy
/dev/.udev/db/block:<name> path which doesn't exist on systemd hosts,
producing one "stat /dev/.udev/db/block:..." warning per device per
collection cycle.
`inputs.diskio` enumerates devices from /proc/diskstats and then opens
/dev/<name> for udev/uevent lookups. The container's /dev only has
docker's minimal set, so telegraf logs an "error reading /dev/<name>"
warning per device per collection cycle. Mount the host's /dev
read-only so device lookups succeed.
Prathamesh Musale