[systemd-devel] Again, why this strange behavior implied by "auto" in fstab ?

[Andrei Borzenkov]

24.01.2018 22:54, Lennart Poettering пишет:
> On Mi, 24.01.18 22:12, Andrei Borzenkov (arvidjaar at gmail.com) wrote:
> 
>> 24.01.2018 22:08, Lennart Poettering пишет:
>>> On Mi, 24.01.18 22:01, Andrei Borzenkov (arvidjaar at gmail.com) wrote:
>>> 1;5002;0c
>>>> 24.01.2018 17:13, Lennart Poettering пишет:
>>>>> On Mi, 24.01.18 14:51, Thomas Blume (Thomas.Blume at suse.com) wrote:
>>>>>
>>>>>> Would this be an acceptable approach?
>>>>>
>>>>> Since a long time there has been a proper API for this: just take a
>>>>> BSD file lock on the device node and udev won't bother with the
>>>>> device anymore. As soon as you close the device fully (and thus also
>>>>> lost all locks), udev will notice and then reprobe it again.
>>>>>
>>>>
>>>> How exactly is udev relevant here? This discussion has nothing to do
>>>> with udev.
>>>
>>> systemd acts on udev's notifications. Other daemons do too. If you
>>> don't want that all those apps and services act on it for your block
>>> device, then the right approach is to block udev from doing so,
>>> i.e. go to the source, not to the symptom.
>>
>> You cannot lock device that does not exist. And as soon as it appears it
>> is mounted.
> 
> hu? Thomas' proposed approach of "systemctl lock $DEVICE" also requires there
> to be a known path for a device, hence it must already be plugged in
> already?
> 
> Also, it's not that systemd takes possession of arbitrary devices just
> like that. It does that because the device was listed explicitly in
> /etc/fstab as "auto" already, and your system wouldn't even have booted if
> the device didn't show up during boot. 
> 

a) If device has "nofail" systemd *will* boot without this device.
b) User is free to unmount and unplug this device even if it was present
in /etc/fstab. And when device is plugged again user may want to change
its content - repartition, reformat, whatever.

> I think you have a different usecase though? Not sure I grok it
> though? you want to turn off all hotplug handling for all future
> devices entirely? what's the usecase?
> 
> Lennart
>