Skip to content

General FAQs - Linux

Multiple kernel partition messages appearing in syslog from the Udev sub-system

By default, the Udev daemon (systemd-udevd) communicates with the kernel and receives device uevents directly from it each time a device is removed or added, or a device changes its state.

Because of the way RSF-1 writes its heartbeats using the ZFS label, the udev sub-system sees this as a state change and erroneously updates syslog each time a heartbeat is transmitted. This can result in multiple messages appearing in syslog of the form:

Aug 10 17:22:24 nodea kernel: [2422456.906302]  sdf: sdf1 sdf9
Aug 10 17:22:24 nodea kernel: [2422456.013538]  sdg: sdg1 sdg9
Aug 10 17:22:25 nodea kernel: [2422458.418906]  sdf: sdf1 sdf9
Aug 10 17:22:25 nodea kernel: [2422458.473936]  sdg: sdg1 sdg9
Aug 10 17:22:25 nodea kernel: [2422459.427251]  sdf: sdf1 sdf9
Aug 10 17:22:25 nodea kernel: [2422459.487747]  sdg: sdg1 sdg9

The underlying reason for this is because Udev watches block devices by binding to the IN_CLOSE_WRITE event from inotify and each time it receives this event a rescan of the device is triggered.

Furthermore newer versions of the ZFS Event Daemon listen to udev events (to manage disk insertion/removal etc.) and catches the udev events generated due to the disk heartbeats, and then attempts to find to which pool (if any) the disk belongs to, resulting in unnecessary I/O.

The solution to this is to add a udev rule that overrides this default behaviour and disables monitoring of the sd* block devices. Add the following to the udev rules file /etc/udev/rules.d/50-rsf.rules1:

ACTION!="remove", KERNEL=="sd*", OPTIONS:="nowatch"

Finally, reload the udev rules to activate the fix.

Thanks to Hervé BRY of Geneanet for this submission.

  1. Udev rules are defined into files with the .rules extension. There are two main locations in which those files can be placed: /usr/lib/udev/rules.d is the directory used for system-installed rules, /etc/udev/rules.d/ is reserved for custom made rules. In this example we've used the name 50-rsf.rules, but any suitable file name can be use. ↩