[systemd-devel] How to delete device units presented in systemd-analyze plot.

[Lennart Poettering]

On Mon, 12.08.13 01:44, Tony Seo (tonyseo7 at gmail.com) wrote:

> I sincerely ask you a relationship between device unit and boot time if I
> remove unnecessary device unit.
> 
> And also, can I ask you detail process of  making device unit by systemd?
> (I alread read the manual page related with device unit)

the kernel creates a directory in /sys for each device popping up. udev
then maintains some additional metadata for all those devices. One part
of that metadata is a "tag" that might be on select devices called
"systemd". If a a device is tagged like that it will also show up as
.device unit systemd. By default block devices, ttys and a few others
are tagged like that. Some services need to wait for some block devices
before they can be run (for example, fsck instances need to wait for
their respective block devices to show up before they can be started),
and this is implemented via dependencies to these device units.

Device units hence are not really something active in themselves, they
just reflect as units state of another component of the OS (which is
udev/kernel).

Lennart

-- 
Lennart Poettering - Red Hat, Inc.