63 lines
3.0 KiB
Markdown
63 lines
3.0 KiB
Markdown
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title = "Local Name Resolution in Arch"
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date = 2020-09-26
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tags = ["admin"]
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It's quite handy to be able to access clients connected at the same Access Point
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as you using their hostname. There are a few technologies to do that : mostly,
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Apple's Bonjour translates as mDNS in the Linux world, then there is Microsoft's
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NetBIOS protocol, that is provided by samba under Linux but not running as a
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default. And Microsoft also created the LLMNR resolution protocol, that ships
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with Windows starting at Vista (and with 7, 8 and 10).
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To have local name resolution, your best option is probably `systemd-resolved`,
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since it does both mDNS and LLMNR. On the other side, avahi does mDNS and lets
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you advertise specific services on the network. If you're interested in this you
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might want to go for it ; check [Archwiki's page on network
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configuration][aw-net-conf]. Here we will deal with `systemd-resolved`.
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The first thing to do is to disable avahi services, since they interfere with
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`systemd-networkd`. Go on and
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```
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# systemctl disable avahi-daemon
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```
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Now we need to check how you do domain resolution on your computer. Under Linux
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this is dependent on who manages `/etc/resolv.conf`. If it's a symlink to some
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NetworkManager folder, it's NetworkManager. If it's linked to some Systemd
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folder, then it's `systemd-resolved`. If it is NetworkManager and you want to
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switch to `systemd-resolved` and keep NetworkManager to manage connections, just
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do :
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```
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# ln -sf /run/systemd/resolve/stub-resolve.conf /etc/resolv.conf
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```
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It may also be a real file, meaning your computer uses static IP addresses for
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DNS servers. In this case you can do the same (back it up if you will).
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Edit `/etc/systemd/resolved.conf` so that inside of the `[Resolve]` section, you
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have `MulticastDNS=yes` and `LLMNR=yes`. After that, you will have to
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```
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# systemctl enable systemd-resolved
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```
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And reboot.
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Now run `resolvectl` to see how it goes. If your network interface doesn't
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specifically allow MulticastDNS, you will have to tell the network manager to do
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it. If it's `systemd-networkd`, you will need to add the very same option in the
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relevant `.network` files in `/etc/systemd/network/`. If it's NetworkManager, no
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luck, you will have to update each and every connection by adding `mdns=2` to
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the `[connection]` section of the connection definition in
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`/etc/NetworkManager/system-connections`.
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If you changed anything, you might want to reboot again. Then try
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```
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$ resolvectl query SOMEHOSTNAME.local
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```
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SOMEHOSTNAME being the name of a device you know is connected. It should answer
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through mDNS. You may also try `resolvectl query SOMEHOSTNAME`, skipping the
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`.local` extension ; it should answer with LLMNR. Do note that Android devices
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don't seem to show up on the local network. But they do see declared neighbours
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; I suspect they ship with LLMNR since they're only able to `ping` names without
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the `.local` extension.
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[aw-net-conf]: https://wiki.archlinux.org/index.php/Network_configuration#Local_network_hostname_resolution
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