Does anybody have experience with both systems enough to compare them?
I’m currently using ifupdown on my Debian server as that’s the default, but it seems that the modern way of managing the local network is via systemd-networkd so I’m contemplating putting the effort in to migrate.
Would those of you who have experience with it, recommend it?
In my short investigation, I have made the following observations:
using networkd means you can use networkctl to manually control the interfaces which is quite convenient
networkd aims to be fully declarative
networkd separates the creation of virtual interfaces (netdev files) from their configuration (network files)
networkd doesn’t support all networking features (e.g. namespaces)
networkd is systemd, but surprisingly I can’t find information on how to create other unit files that depend on the individual network files going up or down, other than networkd-dispatcher. I don’t like dispatcher because just like ifupdown it triggers all the scripts and you need if tests to exclude all interfaces you don’t need to be affected. I’d like to write unit files that can be targeted to activate and deactivate when a particular interface goes up or down.
networkd, other than via dispatcher, does not seem to support adding arbitrary commands to run like ifupdown supports via e.g. pre-down, post-up, etc.
Then I don’t understand why maintainers all keep using network.target.
Because most services are able to dynamically accommodate networking changes and act accordingly and it’s rare to have cases where we really need a working link with addresses and a proper connection when the service starts. For those special cases, as described, you need to enable systemd-networkd-wait-online.service and include After=network-online.target and/or Wants=network-online.target in your service.
Programs should be designed to detect and react to networking changes and both Apache and Nginx are good examples of software that does that. There are simpler cases like stuff that needs to bind to non-existent IPs at boot (before networking) that can be dealt with ipv4.ip_nonlocal_bind and net.ipv6.ip_nonlocal_bind as described here.
I still find it a solution desperately looking for a problem to solve.
Systemd does a LOT more than “you can control loads of dependencies”, it solves tons of painful issues and provides a cohesive ecosystem of tools to manage stuff like:
Start services in parallel (while init was one after the other)
Defer service startup until they are actually needed
Replace a bunch of poorly integrated tools such as dhcpcd, dhcpv6, chrony, NetworkManager, resolvconf, logrotate among others with a cohesive ecosystem of tools that are way easier to work with;
Create full fledged containers both privileged and non-privileged here and here while providing tools such as machinectl to manage them.
Systemd is very useful and most people (including myself) don’t know about half of the things it can do. It isn’t teached because of the current poor state of thing when it comes to software development but if you use it you’ll quickly find how to have systems running very well with less processes than conventionally.
Replace a bunch of poorly integrated tools such as NetworkManager
You got me here… I’m now battling NetworkManager in scripting (alas, still no Ansible in place there, I doubt it’ll be long before I have implemented it), the thing just refuses any configuration via files. Time to dive into the networkd setup. I also hope I can get rid of the very unstable ppoe and wide-dhcpv6-client setup I have here now via ifupdown2 on Debian. The restart I like as well. Time for a deep dive I guess. On Debian NM never caught on, thank $preferredDdiety, but at work it’s a disaster.
I’ll see what I can manage. Thanks for the pointers.
When I can manage simple ipv4 networking via networkd I’m already happy, as it means I can ditch NM again at work, that’s giving me a lot more headaches then a flapping SLAAC that I’m not dependent on. (already switched back to my super stable tunnel) The situation here is a setup with 2 ipv6 tunnels, 1 ipv6 SLAAC, source based routing and no default gateway in main routing table for ipv6. Everything runs via the ipv4 pppoe connection. (and a load of vlans both sides of my router to internet)
Thanks, it was already a mess to figure out without systemd ‘defaults’ barging trough my settings. Maybe I;ll keep my personal setup as it is and only let systemd dat the interface names of the 2 physical interfaces and have the dependencies of services linked to the virtual device states. As long as I can ditch NetworkManager at work I’m totally happy.
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Because most services are able to dynamically accommodate networking changes and act accordingly and it’s rare to have cases where we really need a working link with addresses and a proper connection when the service starts. For those special cases, as described, you need to enable
systemd-networkd-wait-online.serviceand includeAfter=network-online.targetand/orWants=network-online.targetin your service.Programs should be designed to detect and react to networking changes and both Apache and Nginx are good examples of software that does that. There are simpler cases like stuff that needs to bind to non-existent IPs at boot (before networking) that can be dealt with
ipv4.ip_nonlocal_bindandnet.ipv6.ip_nonlocal_bindas described here.This may also interest you as it includes what “up” means a few other details: https://systemd.io/NETWORK_ONLINE/
Systemd does a LOT more than “you can control loads of dependencies”, it solves tons of painful issues and provides a cohesive ecosystem of tools to manage stuff like:
journalctlas a unified interface so you can quickly browse them by specific, filters, timestamps and events.crontabwith something auditable that actually makes sense;machinectlto manage them.Systemd is very useful and most people (including myself) don’t know about half of the things it can do. It isn’t teached because of the current poor state of thing when it comes to software development but if you use it you’ll quickly find how to have systems running very well with less processes than conventionally.
You got me here… I’m now battling NetworkManager in scripting (alas, still no Ansible in place there, I doubt it’ll be long before I have implemented it), the thing just refuses any configuration via files. Time to dive into the networkd setup. I also hope I can get rid of the very unstable ppoe and wide-dhcpv6-client setup I have here now via ifupdown2 on Debian. The restart I like as well. Time for a deep dive I guess. On Debian NM never caught on, thank $preferredDdiety, but at work it’s a disaster.
https://github.com/systemd/systemd/issues/481
wide-dhcpv6-clientis easy, any systemd-networkd IPv6 guide will have what you need.I’ll see what I can manage. Thanks for the pointers.
When I can manage simple ipv4 networking via networkd I’m already happy, as it means I can ditch NM again at work, that’s giving me a lot more headaches then a flapping SLAAC that I’m not dependent on. (already switched back to my super stable tunnel) The situation here is a setup with 2 ipv6 tunnels, 1 ipv6 SLAAC, source based routing and no default gateway in main routing table for ipv6. Everything runs via the ipv4 pppoe connection. (and a load of vlans both sides of my router to internet)
Ahaha that’s gonna take a while to figure out. Good luck.
Btw, policy based routing: https://serverfault.com/questions/682462/how-to-do-policy-routing-with-systemd/877537#877537 and https://www.freedesktop.org/software/systemd/man/systemd.network.html#[RoutingPolicyRule] Section Options
Then I’ll limit myself to the situation at work. ifupdown2 works great and doesn’t need replacing at home.
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Thanks, it was already a mess to figure out without systemd ‘defaults’ barging trough my settings. Maybe I;ll keep my personal setup as it is and only let systemd dat the interface names of the 2 physical interfaces and have the dependencies of services linked to the virtual device states. As long as I can ditch NetworkManager at work I’m totally happy.