lsattr loading modules, changing permissions of device nodes

Michael Biebl biebl at
Tue Mar 16 20:01:52 GMT 2021

Am 16.03.21 um 20:25 schrieb Michael Biebl:
> What you see are the default permissions of the devices. Once the device 
> is marked as ready by the kernel and a uevent is emitted, udev will run 
> its rules and apply the permissions. In this case
> # grep btrfs-control /lib/udev/rules.d/*
> /lib/udev/rules.d/50-udev-default.rules:KERNEL=="btrfs-control", 
> GROUP="disk"
> You can manually trigger a uevent by e.g.
> echo change > /sys/class/misc/btrfs-control/uevent
> Has systemd-udev-trigger.service been run successfully during boot?

For devices which have been initialized by the kernel before udev was 
started, we coldplug them via "udevadm trigger", which sends a change 
uevent and should make sure all udev rules are applied.

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