you can use dmesg -u to see log from userspace. In my case, I have log from systemd and lvm. Why is this happening, why userspace program can print to kernel buffer ring?

2 Answers 2


A root process can write to /dev/kmsg. This is used for logging that occurs very early, before regular logging systems are ready to do any logging.


Some userspace processes can write to the dmesg because they execute actions which used to belong to kernel-space processes, but which have been moved to user-space to allow easier control by users.

A classic example is udev, which, according to Wikipedia:

it handles ... all user space actions when adding/removing devices, including firmware load.

Another well-know example is FUSE, which is:

Filesystem in Userspace (FUSE) is an operating system mechanism for Unix-like computer operating systems that lets non-privileged users create their own file systems without editing kernel code.

Together with LVM, init, and so on, these tools perform kernel operations in user space; for this reason, and possibly also for continuity with the instruments they replaced (devfs, hotplug, ...), their output clearly belongs in the kernel ring buffer.

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