bird3 package upgrades - graceful restart?

[Christoph]

Hello,

Maria Matejka via Bird-users:
> On Mon, Jan 05, 2026 at 12:36:19AM +0100, Christoph via Bird-users wrote:
> 
>     Therefor we are curious whether a bird3 package update will
>     interrupt packet forwarding on a BIRD3 BGP router?
> 
> The package update does not restart BIRD by itself. One must do it 
> manually or scripted themselves.

We updated bird3 now and bird got restarted automatically in this 
process (which is the usual behavior for debian package updates 
unrelated to bird).

apt install bird3
Upgrading:
   bird3

Summary:
   Upgrading: 1, Installing: 0, Removing: 0, Not Upgrading: 2
   Download size: 1,083 kB

Get:1 https://pkg.labs.nic.cz/bird3 trixie/main amd64 bird3 amd64 
3.2.0-cznic.1~trixie [1,083 kB]
Fetched 1,083 kB in 0s (11.1 MB/s)
Reading changelogs... Done
(Reading database ... 60038 files and directories currently installed.)
Preparing to unpack .../bird3_3.2.0-cznic.1~trixie_amd64.deb ...
Unpacking bird3 (3.2.0-cznic.1~trixie) over (3.1.5-cznic.1~trixie) ...
Setting up bird3 (3.2.0-cznic.1~trixie) ...
Processing triggers for man-db (2.13.1-1) ...

At the same time in the log shows the restart without manually 
triggering it:

Jan 05 11:51:47 Stopping bird.service - BIRD Internet Routing Daemon...
Jan 05 11:51:52 bird.service: Deactivated successfully.
Jan 05 11:51:52 Stopped bird.service - BIRD Internet Routing Daemon.
Jan 05 11:51:52 bird.service: Consumed 49min 40.707s CPU time, 1.3G 
memory peak.
Jan 05 11:51:52 Starting bird.service - BIRD Internet Routing Daemon...
Jan 05 11:51:52 Started bird.service - BIRD Internet Routing Daemon.

> I have no idea whether systemd could execute different variants of 
> restart and shutdown, but if it is possible to do so, we might extend 
> our service file in order to execute the restart/shutdown gracefully, 
> regularly or by killing the daemon.
> 
> Or set the behavior by an env var? What do you think?

Since the package update automatically restarts the bird systemd service 
I guess this is what people are used to already so it might be hard to 
change that?

best regards,
Christoph