lsattr loading modules, changing permissions of device nodes

Michael Biebl biebl at
Tue Mar 16 19:25:43 GMT 2021

Hi Marc

Am 16.03.21 um 19:50 schrieb Marc Haber:

> Now friendly and innocent questions towards the udev maintainers:
> * Do you see similiar behavior on your systems?


> * If yes, is this intended behavior?


> * Why does, for example, the /dev/btrfs-control device node get created
>    with one set of owner/mode and then gets converted to a different one
>    when someone accesses it? btrfs-progs are not installed, btrfs is not
>    in use.

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/*

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?

I don't remember any udev related changes which could cause this.

 From which version to which version did you upgrade?

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