Using systemd-networkd vs ifupdown on Debian (kbin.social)

submitted 1 year ago by dr_robot@kbin.social to c/selfhosted@lemmy.world

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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.

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[-] TCB13@lemmy.world 6 points 1 year ago* (last edited 9 months ago)

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[-] dr_robot@kbin.social 0 points 1 year ago

Thanks for your reply! One thing I'm struggling with networkd is hysteresis. That is, toggling the interface down and then back up does not do what I expect it to. That is, setting the interface down does not clear up the configuration, and setting the interface up does not reconfigure the interface. I have to run reconfigure for that. I was hoping that the declarative approach of networkd would make it easy to predict interface state and configuration.

This does make sense because configuration is not the same as operational state. However, what would the equivalent of ifdown (set interface down and remove configuration) and ifup (set interface up and reconfigure) be using networkd and networkctl? This kind of feature would be useful for me to test config changes, debug networking issues, disconnect part of the network while I'm making some changes, etc.

[-] TheInsane42@lemmy.world 3 points 1 year ago* (last edited 1 year ago)

I'm using ifupdown2 and have services depending on the state of virtual network devices (BindsTo=sys-devices-virtual-net-.device).

I hate systemd with a passion, as the refuses to wait for networking when you haven some service specified to be started After networking, but it start when the start of networking actions has sbeen tarted (not after networking is finished bringing up everything)

The only think I let systemd do is monitor the state of the devices and set the interface name, as udev seems to mess these names up in combination with systemd (and there is to much depending on systemd now in Debian to get rid of the junk)

[-] TCB13@lemmy.world 1 points 1 year ago* (last edited 9 months ago)

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[-] TheInsane42@lemmy.world 1 points 1 year ago

If you apply what is written at https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/#cutthecraphowdoimakesurethatmyservicestartsafterthenetworkisreallyonline it will work.

Then I'll need to do a global rewrite of all distrubution delivered service files and replace network.target with network-online.target. Then I don't understand why maintainers all keep using network.target. For every service that needs some kund of netwirj active I alkready have iverrides to link then to the virtual or physical interfaces they actually use.

Systemd-networkd has a learning curve, once you learn it you’ll find it superior and more flexible than anything else.

I still find it a solution desperately looking for a problem to solve. Yes, you can control loads of dependencies, but you could already do that with the init scripts. The main selling point on introduction was 'it is faster'. Why would you want something faster when you use it once every kernel update? When you design your solutions correctly (redundant), you won't even notice a reboot of 1 system in the setup.

[-] TCB13@lemmy.world 2 points 1 year ago* (last edited 9 months ago)

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[-] TheInsane42@lemmy.world 1 points 1 year ago

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.

[-] TCB13@lemmy.world 1 points 1 year ago* (last edited 9 months ago)

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[-] TheInsane42@lemmy.world 1 points 1 year ago

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)

[-] mystik@lemmy.world 3 points 1 year ago

Personally, I will use both: On servers with fixed network connections I will tend to use ifupdown; but on my linux laptops I'll use networkmanager or networkd which tend to have nice UI's for joining various forms of wifi networks. On my laptops for some VPN's i"ll use the ifupdown configuration, which lets me setup all sorts of exotic configurations (bridges, vlans, vxlan,, vpns, namespaces, etc.) The linux command line tooling has a litany of functions to check/test/diagnose/tweak networking settings, and they work across all the distros, AND they can reveal the full details of the network, as the kernel sees it. NetworkManager, networkd, connmann, etc, often omit details in the name of simplifying for the most common scenarios.

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this post was submitted on 05 Aug 2023

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