systemd-networkd-june-ilugc-meet.chatlog

gistfile1.txt

2021-06-12 15:06:43	mohan43u-we	systemd-networkd is part of systemd framework
2021-06-12 15:07:01	mohan43u-we	systemd is the init system in modern linux
2021-06-12 15:07:30	mohan43u-we	apart from init functionality, systemd is capable of doing lot of other things in order to make a linux os usable
2021-06-12 15:07:46	mohan43u-we	one of that functionality is to configure network interface
2021-06-12 15:08:16	mohan43u-we	you can configure a network interface through many ways
2021-06-12 15:08:55	mohan43u-we	as you see in the presenter terminal (in https://meet.ilugc.in), the command 'ip link' will show all the currently available network interfaces
2021-06-12 15:09:16	mohan43u-we	there are physical interfaces as well as virtual network interfaces
2021-06-12 15:09:37	mohan43u-we	you can configure a network interface either static or dynamic
2021-06-12 15:10:29	mohan43u-we	as you see in the presenter terminal, I'm currently showing details about one physical network interface called eth0
2021-06-12 15:10:49	mohan43u-we	the ip address is shown in line 3 as 95.217.160.106
2021-06-12 15:11:04	mohan43u-we	but how does this address got configured
2021-06-12 15:11:15	mohan43u-we	there are many way to configure this ip address
2021-06-12 15:12:03	mohan43u-we	in past, people used ifcfg.up ifcfg.down inside /etc to configure these ip addresses
2021-06-12 15:12:18	mohan43u-we	for dynamic ip configureation, it is done through dhcp
2021-06-12 15:12:48	mohan43u-we	dhcp requires a dhcp server (usually if you have a wireless router in your home, most propbably it will run a dhcp server)
2021-06-12 15:13:20	mohan43u-we	so to dynamically configure a network address for a interface, we used dhcp clients like 'dhcpcd' or 'dhclient'
2021-06-12 15:14:04	mohan43u-we	dhclient is basically a dhcp protocol client which communicates with dhcp server and fetch dynamically assigned ip address for an interface
2021-06-12 15:14:53	mohan43u-we	after dhcpcd/dhclient, NetworkManager was introduced
2021-06-12 15:15:28	mohan43u-we	NetworkManager is also a daemon which manages all the network interfaces in your linux system
2021-06-12 15:15:53	mohan43u-we	it internally uses dhclient for dynamic ip address assigning
2021-06-12 15:16:31	mohan43u-we	if you are using any desktop environment like gnome/kde, you probably use NetworkManager to configure your network interface
2021-06-12 15:16:56	mohan43u-we	but systemd provides much better and faster way to configure network interfaces
2021-06-12 15:17:01	mohan43u-we	it is called systemd-networkd
2021-06-12 15:17:45	mohan43u-we	as you see, my system is also using systemd-networkd to configure network interfaces
2021-06-12 15:18:19	mohan43u-we	infact most of the cloud vm's or containers uses systemd-networkd to configure network interfaces
2021-06-12 15:18:46	mohan43u-we	systemd-networkd uses configuration files to for network interface configuration
2021-06-12 15:19:33	mohan43u-we	if you see the above output, you can see that to configure eth0, systemd-networkd uses a network file called /run/systemd/network/10-netplan-eth0.network
2021-06-12 15:20:20	mohan43u-we	if you look at this file, you can see it contains '[Match]' '[Network]' and '[DHCP]' sections
2021-06-12 15:20:46	mohan43u-we	[Match] section tells which interface this configuration file should be applicable
2021-06-12 15:20:56	mohan43u-we	here it says 'Name=eth0'
2021-06-12 15:21:07	mohan43u-we	that means this configuration file is only for eth0 interface
2021-06-12 15:21:18	mohan43u-we	next [Network] section
2021-06-12 15:21:39	mohan43u-we	in this section, we instruct systemd-networkd to use DHCP (ipv4 address only)
2021-06-12 15:22:29	mohan43u-we	the other variables which configured under [Netowrk] section defines other parameters, we can  ignore them now for context
2021-06-12 15:22:34	mohan43u-we	now, the next section
2021-06-12 15:22:38	mohan43u-we	[DHCP]
2021-06-12 15:23:02	mohan43u-we	this section tells systemd-networkd to use 100 as metric for the routing entry
2021-06-12 15:23:15	mohan43u-we	also it instructs systemd-networkd to use MTU
2021-06-12 15:23:24	mohan43u-we	so thats all, the configuration
2021-06-12 15:24:00	mohan43u-we	using this configuration, at boot, systemd-networkd will try to configure this eth0 interface through dhcp and will fetch only ipv4 address
2021-06-12 15:24:36	mohan43u-we	usually when dhcp server responds, it will tell the ipaddress,netmask, gateway and dns records
2021-06-12 15:24:57	mohan43u-we	systemd-networkd gets these information from dhcp-server and configure them locally
2021-06-12 15:25:25	mohan43u-we	this /etc/resolv.conf file is where dns entries will be configured
2021-06-12 15:25:40	mohan43u-we	normally you see two lines that contains 'nameserver' entries
2021-06-12 15:25:50	mohan43u-we	in my machine also, you can see one 'nameserver' line
2021-06-12 15:26:45	mohan43u-we	in my machine nameserver line tells that dns is done through another daemon running at port 53 (bounded to 127.0.0.53)
2021-06-12 15:27:16	mohan43u-we	as you see, my machine is running a daemon called systemd-resolved at port 53 bounded to 127.0.0.53
2021-06-12 15:27:28	mohan43u-we	it is indicated through 127.0.0.53%lo:53
2021-06-12 15:27:40	mohan43u-we	this systemd-resolved is a dns resolver
2021-06-12 15:28:09	mohan43u-we	when systemd-networkd fetches dns nameserver records from dhcp-server, it will not directly configure it in /etc/resolv.conf
2021-06-12 15:28:29	mohan43u-we	but it passes that information to systemd-resolved, so that systemd-resolved can be used properly
2021-06-12 15:28:52	saikumaran	hi everybody joining late sorry for that
2021-06-12 15:29:17	mohan43u-we	systemd-netoworkd then configure the eth0 interface with the proper dynamically allocated ip address
2021-06-12 15:29:44	mohan43u-we	so, this is how we can use systemd-networkd to configure network interfaces
2021-06-12 15:30:08	mohan43u-we	no need for NetworkManager or any other mechanism to configure dhcp addressing
2021-06-12 15:31:05	mohan43u-we	apart from configuring physical network interfaces
2021-06-12 15:31:17	mohan43u-we	systemd-networkd can also create virtual interfaces dynamically
2021-06-12 15:31:46	mohan43u-we	before I move onto this section of my talk, let me know if you have any questions
2021-06-12 15:32:26	mohan43u-we	ok, lets continue
2021-06-12 15:32:40	mohan43u-we	now, we will create one simple bridge interface through systemd-networkd
2021-06-12 15:33:35	mohan43u-we	I'm going to create one file with .netdev extension
2021-06-12 15:34:01	mohan43u-we	systemd-networkd understand .netdev files and create virtual network interfaces as per the configuration
2021-06-12 15:34:35	mohan43u-we	you can see all the variables to use in .netdev through 'man systemd.netdev' manual page
2021-06-12 15:35:06	mohan43u-we	systemd-networkd can create all the virtual networks available in linux
2021-06-12 15:35:23	mohan43u-we	you can see the types of virtual networks it ca create in the manual page
2021-06-12 15:35:37	mohan43u-we	one such interface is bridge
2021-06-12 15:35:49	mohan43u-we	bridge is nothing but a simple multiplexer
2021-06-12 15:36:26	mohan43u-we	you can attach physical interfaces to a bridge interface and make two physical network communicate with each other
2021-06-12 15:39:46	mohan43u-we	as you see
2021-06-12 15:39:56	mohan43u-we	I just created one bridge interface called sbr0
2021-06-12 15:40:14	mohan43u-we	you can also see that interface through ip link
2021-06-12 15:41:01	mohan43u-we	as you see, the sbr0 is created by systemd-networkd
2021-06-12 15:41:46	mohan43u-we	you can now, create or delete a virtual network interface as you want through networkctl
2021-06-12 15:42:32	mohan43u-we	networkctl reload means, we instruct the currently running systemd-networkd to re read all the configuration files again
2021-06-12 15:42:54	mohan43u-we	you can create configuration files for systemd-networkd in /etc/systemd/network directory
2021-06-12 15:43:03	mohan43u-we	/run/systemd/network directory
2021-06-12 15:43:11	mohan43u-we	/usr/lib/systemd/network directory
2021-06-12 15:44:19	mohan43u-we	/etc/systemd/network directory is the top most, means, the files in this directory overrides all other directories
2021-06-12 15:45:09	mohan43u-we	so, this is how we use sysetmd-netowrkd
2021-06-12 15:45:26	mohan43u-we	to configure/create network in modern linux
2021-06-12 15:45:44	mohan43u-we	man systemd.network
2021-06-12 15:45:58	mohan43u-we	this manual page provides all the details you need to create .network files
2021-06-12 15:46:10	mohan43u-we	man systemd.netdev
2021-06-12 15:46:28	mohan43u-we	this manual page provides all the details you need to create virtual network interfaces using .netdev files
2021-06-12 15:46:42	mohan43u-we	man systemd.link
2021-06-12 15:47:16	mohan43u-we	this manual page provides all the details to configure layer2 for a network interface (including assigning a name to network interface)
2021-06-12 15:47:33	mohan43u-we	thats all from my talk
2021-06-12 15:47:44	mohan43u-we	if you have any questions, ask
2021-06-12 15:49:07	mohan43u-we	I hope this talk will be useful to you. use systemd-networkd to configure your network interfaces. it is very simple and straight forward
2021-06-12 15:49:28	mohan43u-we	no more NetworkManager crap
2021-06-12 15:49:47	mohan43u-we	just straight forward configuration files
2021-06-12 15:49:57	mohan43u-we	and it is damn faster
2021-06-12 15:50:12	mohan43u-we	integrates better with other systemd components
2021-06-12 15:50:25	mohan43u-we	like systemd-resolved
2021-06-12 15:50:37	mohan43u-we	thanks
2021-06-12 15:50:55	mohan43u-we	over to nihaal for his presentation