[systemd-devel] why does nofail imply no After= in /etc/fstab

[Kay Sievers]

On Thu, Jan 16, 2014 at 4:19 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Thu, 16.01.14 16:14, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
>
>>
>> On Thu, Jan 16, 2014 at 03:51:02PM +0100, Lennart Poettering wrote:
>> > On Wed, 15.01.14 20:20, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
>> >
>> > > I was a bit surprised that for mount points the dependency
>> > > Before=local-fs.target is only added when nofail is not used.
>> > > This seems to be a concious decision (added by Lennart in
>> > > 155da457, and then survived all the refactorings by Tom
>> > > and Thomas...). Do we still want this behaviour?
>> >
>> > Well, "nofail" means that we shouldn't bother if the device doesn't show
>> > up at boot. Now, if we add "After=" for it there, then we will time-out
>> > on it (though not fail) if something else pulls it in.
>> >
>> > I figure this is a question what nofail really should mean: "never wait
>> > for it, never fail for it" (which is the status quo), or just "usually
>> > don't wait, never fail for it" (which would be the change if we added
>> > After= in). I am tempted to say that the status quo is more likely what
>> > people would expect, no?
>>
>> The problem is that with current boot speeds, "usually don't wait" means
>> that it shows up at some "upredictable" time. With a bit of luck, users
>> might be able to log in before such mount points which are declared in
>> /etc/fstab are mounted. I think that's unexpected, because it goes againt
>> the general rule that things declared in /etc/fstab (w/o automount or noauto)
>> are mounted at boot.
>
> I'd argue that "nofail" is precisely what the admin can use to *enable*
> this race. If it should be avoided to allow the user to log in before
> the device has shown up and is hooked in the admin should not have used
> "nofail"...
>
>> I'd prefer to keep things orthogonal. This feels like an "optimization"
>> that it user visible. We should rather encourage people to use automounts
>> if the don't want to wait for the mountpoint to come up.
>
> I am pretty sure people would be annoyed by this change of behaviour,
> simply because every boot would still delay for 90s if the device is not
> plugged in. I have the suspicion that people would really assume that
> using "nofail" would make their system boot-up cleanly, without delays
> if the file system cannot be found -- and that expection is something
> we'd not fulfill?

man mount 8:
nofail -- Do not report errors for this device if it does not exist.

Right, we cannot really re-define this. It's use is established since years.
Used for things like isci, which is often not available at bootup.

Kay