[systemd-devel] [PATCH] systemd-udevd.service: restore mount propagation

Lennart Poettering lennart at poettering.net
Tue Jan 27 13:46:05 PST 2015

On Tue, 27.01.15 17:22, Lennart Poettering (lennart at poettering.net) wrote:

> On Tue, 27.01.15 16:24, Martin Pitt (martin.pitt at ubuntu.com) wrote:
> > > Well, again, the right answer then is to handle it with .mount units,
> > 
> > How would that look like, on a very high level? Create .mount units on
> > the fly with udev rules when devices appear, and asking systemd to
> > unmount them via a remove uevent, instead of having cdrom_id do the
> > umount directly?
> The .mount units of device nodes already have a BindsTo= dependency on
> their respective backing .device units. This should have the effect
> that systemd will take the .mount units down if the .device units are
> removed. Are you saying that doesn't work?

So I figure the bit that is missing here is the fact that the .device
units for CD drives and USB card readers don't care for media sense right
now. The .device units for CD drives and USB card readers are
available as long as the CD drive or USB card reader is plugged in, it
doesn't care for any media being in it. That means that automatic
unmounting by systemd due to the device going away will only happen if
you actually unplug the CD driver or the USB card, but not already
when the media is ejected.

However, I think it would make a ton of sense to change that, and set
SYSTEMD_READY=0 on all block devices where the media sensing suggests
that no medium is in it. This would mean that these devices don't show
up as systemd units until you actually put a medium in it. That would
be a change of semantics, but I think a useful one. 

What do you think?


Lennart Poettering, Red Hat

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