174 lines
4.4 KiB
XML
174 lines
4.4 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xml:id="ch-configuration">
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<title>Configuring NixOS</title>
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<para>This chapter describes how to configure various aspects of a
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NixOS machine through the configuration file
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<filename>/etc/nixos/configuration.nix</filename>. As described in
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<xref linkend="sec-changing-config" />, changes to that file only take
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effect after you run <command>nixos-rebuild</command>.</para>
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<!--===============================================================-->
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<section><title>Networking</title>
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<section><title>Secure shell access</title>
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<para>Secure shell (SSH) access to your machine can be enabled by
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setting:
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<programlisting>
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services.openssh.enable = true;
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</programlisting>
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By default, root logins using a password are disallowed. They can be
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disabled entirely by setting
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<literal>services.openssh.permitRootLogin</literal> to
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<literal>"no"</literal>.</para>
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<para>You can declaratively specify authorised RSA/DSA public keys for
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a user as follows:
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<!-- FIXME: this might not work if the user is unmanaged. -->
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<programlisting>
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users.extraUsers.alice.openssh.authorizedKeys.keys =
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[ "ssh-dss AAAAB3NzaC1kc3MAAACBAPIkGWVEt4..." ];
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</programlisting>
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</para>
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</section>
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<section><title>IPv4 configuration</title>
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<para>By default, NixOS uses DHCP (specifically,
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(<command>dhcpcd</command>)) to automatically configure network
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interfaces. However, you can configure an interface manually as
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follows:
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<programlisting>
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networking.interfaces.eth0 = { ipAddress = "192.168.1.2"; prefixLength = 24; };
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</programlisting>
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(The network prefix can also be specified using the option
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<literal>subnetMask</literal>,
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e.g. <literal>"255.255.255.0"</literal>, but this is deprecated.)
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Typically you’ll also want to set a default gateway and set of name
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servers:
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<programlisting>
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networking.defaultGateway = "192.168.1.1";
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networking.nameservers = [ "8.8.8.8" ];
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</programlisting>
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</para>
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<note><para>Statically configured interfaces are set up by the systemd
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service
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<replaceable>interface-name</replaceable><literal>-cfg.service</literal>.
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The default gateway and name server configuration is performed by
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<literal>network-setup.service</literal>.</para></note>
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<para>The host name is set using <option>networking.hostName</option>:
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<programlisting>
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networking.hostName = "cartman";
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</programlisting>
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The default host name is <literal>nixos</literal>. Set it to the
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empty string (<literal>""</literal>) to allow the DHCP server to
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provide the host name.</para>
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</section>
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<section><title>IPv6 configuration</title>
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<para>IPv6 is enabled by default. Stateless address autoconfiguration
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is used to automatically assign IPv6 addresses to all interfaces. You
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can disable IPv6 support globally by setting:
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<programlisting>
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networking.enableIPv6 = false;
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</programlisting>
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</para>
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</section>
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<section><title>Firewall</title>
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<para>NixOS has a simple stateful firewall that blocks incoming
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connections and other unexpected packets. The firewall applies to
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both IPv4 and IPv6 traffic. It can be enabled as follows:
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<programlisting>
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networking.firewall.enable = true;
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</programlisting>
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You can open specific TCP ports to the outside world:
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<programlisting>
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networking.firewall.allowedTCPPorts = [ 80 443 ];
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</programlisting>
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Note that TCP port 22 (ssh) is opened automatically if the SSH daemon
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is enabled (<option>services.openssh.enable = true</option>). UDP
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ports can be opened through
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<option>networking.firewall.allowedUDPPorts</option>. Also of
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interest is
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<programlisting>
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networking.firewall.allowPing = true;
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</programlisting>
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to allow the machine to respond to ping requests. (ICMPv6 pings are
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always allowed.)</para>
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</section>
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<section><title>Wireless networks</title>
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<para>TODO</para>
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</section>
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<section><title>Ad-hoc configuration</title>
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<para>You can use <option>networking.localCommands</option> to specify
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shell commands to be run at the end of
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<literal>network-setup.service</literal>. This is useful for doing
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network configuration not covered by the existing NixOS modules. For
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instance, to statically configure an IPv6 address:
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<programlisting>
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networking.localCommands =
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''
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ip -6 addr add 2001:610:685:1::1/64 dev eth0
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'';
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</programlisting>
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</para>
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</section>
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<!-- TODO: OpenVPN, NAT -->
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</section>
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<!-- TODO: declarative package installation; X11; user management;
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Apache; libvirtd virtualisation -->
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</chapter>
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