[systemd-devel] Help needed for optimizing my boot time

[Francis Moreau]

On 06/12/2015 06:26 PM, Andrei Borzenkov wrote:
> В Fri, 12 Jun 2015 16:56:08 +0200
> Francis Moreau <francis.moro at gmail.com> пишет:
> 
>> On 06/11/2015 06:23 PM, Dan Williams wrote:
>>> On Thu, 2015-06-11 at 15:15 +0200, Francis Moreau wrote:
>> [...]
>>>>
>>>> Does ntpd service really need 'After=network.target', not sure.
>>>
>>> The 'network online' targets are really just there for ignorant services
>>> that don't respond to network events themselves, that expect the network
>>> to be up and running before they start.  Of course, those services don't
>>> have any way to say *which* network interface they care about, so if you
>>> have more than one interface in your system they still get it wrong.
>>
>> Do such services exist actually ?
>>
> 
> Until recently ntpd required working name resolution (i.e. often DNS)
> to find its peers. If you mount something over network on boot you want
> to have reasonable confidence that network is up.
> 
>> I can't see how such service can work if they can't handle the offline
>> case properly...
>>
> 
> Please explain how filesystem on iSCSI target is supposed to handle
> offline case properly. 
> 

I was talking about ntpd, I dont know for you specific case.

>> BTW 'network online' target doesn't seem to mean the network is up
>> because if I boot my computer offline, this target is still reached and
>> passed.
>>
> 
> Yes, network-online.target is not there to make boot impossible; it is
> there to delay boot until network is considered to be up. It makes
> little sense in pure dynamic environment; it is quite useful in static
> server environment where network is expected to be always present but
> may take some time to be configured.
>

Then if it's not reliable in some cases how can it be used by some
generic services such as ntpd if ntpd is not prepared to handle the
offline case ?

>>>
>>> But anyway, if ntpd or autofs can respond to network events using
>>> netlink or listening on D-Bus to NetworkManager/connman/etc or getting
>>> triggered by eg NetworkManager dispatcher scripts, then they probably
>>> don't need to block on network-online.  But if they can't, and they
>>> expect the network to be up and running before they start, then yes they
>>> will block startup until some kind of networking is running.
>>
>> Well I must be missing something but I can't see why ntpd or autofs
>> would rely and have any deps on NM whereas they need to deal with the
>> generic case, i.e. the one where NM is not installed and used.
>>
> 
> Where do you see any deps on NM? network-online.target is generic
> target which will be used with any underlying networking implementation.

I was refering to "if ntpd or autofs can respond to network events using
netlink or listening on D-Bus to NetworkManager/connman/etc"

>>
>> IOW, any services having "After: network-online.target" look odd to me.
>>
> 
> Welcome to real world :)
> 

No, real world is not "wait for ntpd, autofs to be activated before I
can login" or at least not in my world ;)

I don't really understand your opinion, are you saying that ntpd should
used "After: network-online.target" ?

Thanks