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systemd: how to start a service (kea DHCP4) after all network interfaces are up?

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  systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2019-03-16 12:50 +0100
    Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? john doe <johndoe65534@mail.com> - 2019-03-16 14:40 +0100
      Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2019-03-16 19:40 +0100
        Re: systemd: how to start a service (kea DHCP4) after all network interfaces are up? Sven Joachim <svenjoac@gmx.de> - 2019-03-16 21:30 +0100
          Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2019-03-17 17:20 +0100
    Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Greg Wooledge <wooledg@eeg.ccf.org> - 2019-03-18 13:50 +0100
      Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2019-03-18 14:30 +0100
        Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Curt <curty@free.fr> - 2019-03-18 18:50 +0100
    Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Henning Follmann <hfollmann@itcfollmann.com> - 2019-03-18 20:30 +0100
      Re: systemd: how to start a service (kea DHCP4) after all network  interfaces are up? Markus Schönhaber <debian-user@list-post.mks-mail.de> - 2019-03-18 21:00 +0100

#206274 — systemd: how to start a service (kea DHCP4) after all network interfaces are up?

Hi,

I have installed the kea DHCP4 server on a machine running recent
stretch and two ethernet interfaces. kea is configured to answer DHCP
requests on one of the interfaces.
On boot, the kea-dhcp4-server.service is started but doesn't work. It
logs this:
> DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: the interface enp3s0 is down or has no usable IPv4 addresses configured
After manually restarting the service it works fine.

It seems that the DHCP server is started while the interface it is
configured to listen on is not yet up and therefore refuses to work.
How can I make sure that the kea-dhcp4-server.service is started no
sooner than after all network interfaces are up?

What I've tried:
1 Copied /lib/systemd/system/kea-dhcp4-server.service to
  /etc/systemd/system and added
  Wants=networking.service
  After=networking.service
  to the [Unit] section of the copy.
  The problem remained.
2 Created a shell script that does a
  sleep 5
  before exec'ing the original
  /usr/sbin/kea-dhcp4 -c /etc/kea/kea-dhcp4.conf
  and replaced the unit's ExexStart line with the path to this script.

2 does indeed help: the dhcp server works as it should after a reboot.
Well, this is a workaround at best, a terrible mess at worst, but it's
definitely not a solution. So I hope someone can answer my question above.

-- 
Regards
  mks

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#206275

On 3/16/2019 12:31 PM, Markus Schönhaber wrote:
> Hi,
>
> I have installed the kea DHCP4 server on a machine running recent
> stretch and two ethernet interfaces. kea is configured to answer DHCP
> requests on one of the interfaces.
> On boot, the kea-dhcp4-server.service is started but doesn't work. It
> logs this:
>> DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: the interface enp3s0 is down or has no usable IPv4 addresses configured
> After manually restarting the service it works fine.
>
> It seems that the DHCP server is started while the interface it is
> configured to listen on is not yet up and therefore refuses to work.
> How can I make sure that the kea-dhcp4-server.service is started no
> sooner than after all network interfaces are up?
>
> What I've tried:
> 1 Copied /lib/systemd/system/kea-dhcp4-server.service to
>   /etc/systemd/system and added
>   Wants=networking.service
>   After=networking.service
>   to the [Unit] section of the copy.
>   The problem remained.
> 2 Created a shell script that does a
>   sleep 5
>   before exec'ing the original
>   /usr/sbin/kea-dhcp4 -c /etc/kea/kea-dhcp4.conf
>   and replaced the unit's ExexStart line with the path to this script.
>
> 2 does indeed help: the dhcp server works as it should after a reboot.
> Well, this is a workaround at best, a terrible mess at worst, but it's
> definitely not a solution. So I hope someone can answer my question above.
>

If your interface is configured by 'systemd', you could try:

$ systemctl enable systemd-networkd-wait-online

--
John Doe

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#206276

John Doe, 16.3.2019 14:18 +0100:

> If your interface is configured by 'systemd', you could try:
> 
> $ systemctl enable systemd-networkd-wait-online

Thanks, but no, my network configuration is done through
/etc/network/interfaces. Therefore this won't help.

-- 
Regards
  mks

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#206277 — Re: systemd: how to start a service (kea DHCP4) after all network interfaces are up?

On 2019-03-16 19:20 +0100, Markus Schönhaber wrote:

> John Doe, 16.3.2019 14:18 +0100:
>
>> If your interface is configured by 'systemd', you could try:
>> 
>> $ systemctl enable systemd-networkd-wait-online
>
> Thanks, but no, my network configuration is done through
> /etc/network/interfaces. Therefore this won't help.

Try "systemctl enable ifupdown-wait-online.service" then.
See bug #912112[1].

Cheers,
       Sven


1. https://bugs.debian.org/912112

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#206286

Sven Joachim, 16.3.2019 21:11 +0100:

> On 2019-03-16 19:20 +0100, Markus Schönhaber wrote:
> 
>> John Doe, 16.3.2019 14:18 +0100:
>>
>>> If your interface is configured by 'systemd', you could try:
>>>
>>> $ systemctl enable systemd-networkd-wait-online
>>
>> Thanks, but no, my network configuration is done through
>> /etc/network/interfaces. Therefore this won't help.
> 
> Try "systemctl enable ifupdown-wait-online.service" then.
> See bug #912112[1].

Thanks for the info! But alas, since I'm on stretch, it isn't that
easy, since the ifupdown package there provides neither the
ifupdown-wait-online.service file nor the wait-online.sh script.
I've downloaded the .deb for buster and tried to extract the relevant
files from there and install them on my system, but I didn't manage to
get that working in a way that the DHCP server was kept from starting
too early.
Due to the lack of time I'll refrain from trying to find out what I may
have done wrong. And since there seems to be no out-of-the-box solution
for this problem on stretch anyway, I'll stick to my ugly workaround for
now and hope this will be sorted out in buster.

That said, thanks again for pointing me in the right direction!

-- 
Regards
  mks

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#206302

On Sat, Mar 16, 2019 at 12:31:50PM +0100, Markus Schönhaber wrote:
> It seems that the DHCP server is started while the interface it is
> configured to listen on is not yet up and therefore refuses to work.
> How can I make sure that the kea-dhcp4-server.service is started no
> sooner than after all network interfaces are up?

1) Make sure the interface is marked "auto" and NOT "allow-hotplug"
   in /etc/network/interfaces.

   Interfaces that are marked "auto" are required to be up before systemd
   will consider network-online.target to be satisfied.  Interfaces that
   are marked "allow-hotplug" are NOT required to be up.

   Note that the Debian installer marks all interfaces except loopback
   as "allow-hotplug" because it assumes you're using a laptop with a
   Wifi or removable USB network interface, even if the interface is
   actually PCI and internal, or even soldered to the motherboard, even
   if the machine you're installing on is a desktop PC or a rack-mounted
   server.

2) Make sure your service has

[Unit]
Wants= network-online.target
After= network-online.target

   either in the native unit file, or in a local drop-in directory.

   Services with these options will wait for all network interfaces that
   are marked "auto" to be brought up, before these services can be
   started.

Don't forget the daemon-reload.

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#206306

Greg Wooledge, 18.3.2019 13:30 +0100:

> On Sat, Mar 16, 2019 at 12:31:50PM +0100, Markus Schönhaber wrote:
>> It seems that the DHCP server is started while the interface it is
>> configured to listen on is not yet up and therefore refuses to work.
>> How can I make sure that the kea-dhcp4-server.service is started no
>> sooner than after all network interfaces are up?
> 
> 1) Make sure the interface is marked "auto" and NOT "allow-hotplug"
>    in /etc/network/interfaces.
> 
>    Interfaces that are marked "auto" are required to be up before systemd
>    will consider network-online.target to be satisfied.  Interfaces that
>    are marked "allow-hotplug" are NOT required to be up.
> 
>    Note that the Debian installer marks all interfaces except loopback
>    as "allow-hotplug" because it assumes you're using a laptop with a
>    Wifi or removable USB network interface, even if the interface is
>    actually PCI and internal, or even soldered to the motherboard, even
>    if the machine you're installing on is a desktop PC or a rack-mounted
>    server.
> 
> 2) Make sure your service has
> 
> [Unit]
> Wants= network-online.target
> After= network-online.target
> 
>    either in the native unit file, or in a local drop-in directory.
> 
>    Services with these options will wait for all network interfaces that
>    are marked "auto" to be brought up, before these services can be
>    started.

1) and 2) was already the case on my machine. Nevertheless the service
was started before the needed interface was up.
That's why I asked in the first place.

Judging from the info in the other answers I got, it's obviously known
that 1) and 2) are *not* enough to make sure the start of such a service
is delayed until the required interfaces are up.

-- 
Regards
  mks

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#206326

On 2019-03-18, Markus Schönhaber <debian-user@list-post.mks-mail.de> wrote:
> Greg Wooledge, 18.3.2019 13:30 +0100:
>
>> On Sat, Mar 16, 2019 at 12:31:50PM +0100, Markus Schönhaber wrote:
>>> It seems that the DHCP server is started while the interface it is
>>> configured to listen on is not yet up and therefore refuses to work.
>>> How can I make sure that the kea-dhcp4-server.service is started no
>>> sooner than after all network interfaces are up?
>> 
>> 1) Make sure the interface is marked "auto" and NOT "allow-hotplug"
>>    in /etc/network/interfaces.
>> 
>>    Interfaces that are marked "auto" are required to be up before systemd
>>    will consider network-online.target to be satisfied.  Interfaces that
>>    are marked "allow-hotplug" are NOT required to be up.
>> 
>>    Note that the Debian installer marks all interfaces except loopback
>>    as "allow-hotplug" because it assumes you're using a laptop with a
>>    Wifi or removable USB network interface, even if the interface is
>>    actually PCI and internal, or even soldered to the motherboard, even
>>    if the machine you're installing on is a desktop PC or a rack-mounted
>>    server.
>> 
>> 2) Make sure your service has
>> 
>> [Unit]
>> Wants= network-online.target
>> After= network-online.target
>> 
>>    either in the native unit file, or in a local drop-in directory.
>> 
>>    Services with these options will wait for all network interfaces that
>>    are marked "auto" to be brought up, before these services can be
>>    started.
>
> 1) and 2) was already the case on my machine. Nevertheless the service
> was started before the needed interface was up.
> That's why I asked in the first place.
>
> Judging from the info in the other answers I got, it's obviously known
> that 1) and 2) are *not* enough to make sure the start of such a service
> is delayed until the required interfaces are up.
>

Workaround help perhaps in this thread:

https://unix.stackexchange.com/questions/209832/debian-systemd-network-online-target-not-working/217768

-- 
“Let us again pretend that life is a solid substance, shaped like a globe,
which we turn about in our fingers. Let us pretend that we can make out a plain
and logical story, so that when one matter is despatched--love for instance--
we go on, in an orderly manner, to the next.” - Virginia Woolf, The Waves

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#206331

On Sat, Mar 16, 2019 at 12:31:50PM +0100, Markus Schönhaber wrote:
> Hi,
> 
> I have installed the kea DHCP4 server on a machine running recent
> stretch and two ethernet interfaces. kea is configured to answer DHCP
> requests on one of the interfaces.
> On boot, the kea-dhcp4-server.service is started but doesn't work. It
> logs this:
> > DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: the interface enp3s0 is down or has no usable IPv4 addresses configured
> After manually restarting the service it works fine.
> 
> It seems that the DHCP server is started while the interface it is
> configured to listen on is not yet up and therefore refuses to work.
> How can I make sure that the kea-dhcp4-server.service is started no
> sooner than after all network interfaces are up?
> 
> What I've tried:
> 1 Copied /lib/systemd/system/kea-dhcp4-server.service to
>   /etc/systemd/system and added
>   Wants=networking.service
>   After=networking.service
>   to the [Unit] section of the copy.
>   The problem remained.
> 2 Created a shell script that does a
>   sleep 5
>   before exec'ing the original
>   /usr/sbin/kea-dhcp4 -c /etc/kea/kea-dhcp4.conf
>   and replaced the unit's ExexStart line with the path to this script.
> 
> 2 does indeed help: the dhcp server works as it should after a reboot.
> Well, this is a workaround at best, a terrible mess at worst, but it's
> definitely not a solution. So I hope someone can answer my question above.
> 
> -- 
> Regards
>   mks
> 


I am coming late to this thread. 
Have you considered to switch from /e/n/i to systemd-networkd?
I think that would solve the problem.

-H

-- 
Henning Follmann           | hfollmann@itcfollmann.com

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#206334

Henning Follmann, 18.3.2019 20:07 +0100:

> Have you considered to switch from /e/n/i to systemd-networkd?
> I think that would solve the problem.

No, I'm not considering to switch the entire way of configuring the
network just to (maybe) get something working which I'd call a pretty
basic feature. I don't even know what else might be affected by such a
switch (scripts in if-up.d, whatever...).

-- 
Regards
  mks

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