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uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

Browse source 
https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>
This commit is contained in:
Anton Arapov 2021-04-03 12:58:10 +02:00 • committed by Alan Daniels
commit 56de2bcd43
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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-building-image">
<title>Building a NixOS (Live) ISO</title>
<para>
Default live installer configurations are available inside
<literal>nixos/modules/installer/cd-dvd</literal>. For building
other system images,
<link xlink:href="https://github.com/nix-community/nixos-generators">nixos-generators</link>
is a good place to start looking at.
</para>
<para>
You have two options:
</para>
<itemizedlist spacing="compact">
<listitem>
<para>
Use any of those default configurations as is
</para>
</listitem>
<listitem>
<para>
Combine them with (any of) your host config(s)
</para>
</listitem>
</itemizedlist>
<para>
System images, such as the live installer ones, know how to enforce
configuration settings on wich they immediately depend in order to
work correctly.
</para>
<para>
However, if you are confident, you can opt to override those
enforced values with <literal>mkForce</literal>.
</para>
<section xml:id="sec-building-image-instructions">
<title>Practical Instructions</title>
<programlisting>
$ git clone https://github.com/NixOS/nixpkgs.git
$ cd nixpkgs/nixos
$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-minimal.nix default.nix
</programlisting>
<para>
To check the content of an ISO image, mount it like so:
</para>
<programlisting>
# mount -o loop -t iso9660 ./result/iso/cd.iso /mnt/iso
</programlisting>
</section>
<section xml:id="sec-building-image-drivers">
<title>Additional drivers or firmware</title>
<para>
If you need additional (non-distributable) drivers or firmware in
the installer, you might want to extend these configurations.
</para>
<para>
For example, to build the GNOME graphical installer ISO, but with
support for certain WiFi adapters present in some MacBooks, you
can create the following file at
<literal>modules/installer/cd-dvd/installation-cd-graphical-gnome-macbook.nix</literal>:
</para>
<programlisting language="bash">
{ config, ... }:
{
imports = [ ./installation-cd-graphical-gnome.nix ];
boot.initrd.kernelModules = [ &quot;wl&quot; ];
boot.kernelModules = [ &quot;kvm-intel&quot; &quot;wl&quot; ];
boot.extraModulePackages = [ config.boot.kernelPackages.broadcom_sta ];
}
</programlisting>
<para>
Then build it like in the example above:
</para>
<programlisting>
$ git clone https://github.com/NixOS/nixpkgs.git
$ cd nixpkgs/nixos
$ export NIXPKGS_ALLOW_UNFREE=1
$ nix-build -A config.system.build.isoImage -I nixos-config=modules/installer/cd-dvd/installation-cd-graphical-gnome-macbook.nix default.nix
</programlisting>
</section>
<section xml:id="sec-building-image-tech-notes">
<title>Technical Notes</title>
<para>
The config value enforcement is implemented via
<literal>mkImageMediaOverride = mkOverride 60;</literal> and
therefore primes over simple value assignments, but also yields to
<literal>mkForce</literal>.
</para>
<para>
This property allows image designers to implement in semantically
correct ways those configuration values upon which the correct
functioning of the image depends.
</para>
<para>
For example, the iso base image overrides those file systems which
it needs at a minimum for correct functioning, while the installer
base image overrides the entire file system layout because there
can’t be any other guarantees on a live medium than those given by
the live medium itself. The latter is especially true befor
formatting the target block device(s). On the other hand, the
netboot iso only overrides its minimum dependencies since netboot
images are always made-to-target.
</para>
</section>
</chapter>

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-changing-config">
<title>Changing the Configuration</title>
<para>
The file <literal>/etc/nixos/configuration.nix</literal> contains
the current configuration of your machine. Whenever you’ve
<link linkend="ch-configuration">changed something</link> in that
file, you should do
</para>
<programlisting>
# nixos-rebuild switch
</programlisting>
<para>
to build the new configuration, make it the default configuration
for booting, and try to realise the configuration in the running
system (e.g., by restarting system services).
</para>
<warning>
<para>
This command doesn't start/stop
<link linkend="opt-systemd.user.services">user services</link>
automatically. <literal>nixos-rebuild</literal> only runs a
<literal>daemon-reload</literal> for each user with running user
services.
</para>
</warning>
<warning>
<para>
These commands must be executed as root, so you should either run
them from a root shell or by prefixing them with
<literal>sudo -i</literal>.
</para>
</warning>
<para>
You can also do
</para>
<programlisting>
# nixos-rebuild test
</programlisting>
<para>
to build the configuration and switch the running system to it, but
without making it the boot default. So if (say) the configuration
locks up your machine, you can just reboot to get back to a working
configuration.
</para>
<para>
There is also
</para>
<programlisting>
# nixos-rebuild boot
</programlisting>
<para>
to build the configuration and make it the boot default, but not
switch to it now (so it will only take effect after the next
reboot).
</para>
<para>
You can make your configuration show up in a different submenu of
the GRUB 2 boot screen by giving it a different <emphasis>profile
name</emphasis>, e.g.
</para>
<programlisting>
# nixos-rebuild switch -p test
</programlisting>
<para>
which causes the new configuration (and previous ones created using
<literal>-p test</literal>) to show up in the GRUB submenu
<quote>NixOS - Profile 'test'</quote>. This can be useful to
separate test configurations from <quote>stable</quote>
configurations.
</para>
<para>
Finally, you can do
</para>
<programlisting>
$ nixos-rebuild build
</programlisting>
<para>
to build the configuration but nothing more. This is useful to see
whether everything compiles cleanly.
</para>
<para>
If you have a machine that supports hardware virtualisation, you can
also test the new configuration in a sandbox by building and running
a QEMU <emphasis>virtual machine</emphasis> that contains the
desired configuration. Just do
</para>
<programlisting>
$ nixos-rebuild build-vm
$ ./result/bin/run-*-vm
</programlisting>
<para>
The VM does not have any data from your host system, so your
existing user accounts and home directories will not be available
unless you have set <literal>mutableUsers = false</literal>. Another
way is to temporarily add the following to your configuration:
</para>
<programlisting language="bash">
users.users.your-user.initialHashedPassword = &quot;test&quot;;
</programlisting>
<para>
<emphasis>Important:</emphasis> delete the $hostname.qcow2 file if
you have started the virtual machine at least once without the right
users, otherwise the changes will not get picked up. You can forward
ports on the host to the guest. For instance, the following will
forward host port 2222 to guest port 22 (SSH):
</para>
<programlisting>
$ QEMU_NET_OPTS=&quot;hostfwd=tcp::2222-:22&quot; ./result/bin/run-*-vm
</programlisting>
<para>
allowing you to log in via SSH (assuming you have set the
appropriate passwords or SSH authorized keys):
</para>
<programlisting>
$ ssh -p 2222 localhost
</programlisting>
</chapter>

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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-installing-behind-proxy">
<title>Installing behind a proxy</title>
<para>
To install NixOS behind a proxy, do the following before running
<literal>nixos-install</literal>.
</para>
<orderedlist numeration="arabic">
<listitem>
<para>
Update proxy configuration in
<literal>/mnt/etc/nixos/configuration.nix</literal> to keep the
internet accessible after reboot.
</para>
<programlisting language="bash">
networking.proxy.default = &quot;http://user:password@proxy:port/&quot;;
networking.proxy.noProxy = &quot;127.0.0.1,localhost,internal.domain&quot;;
</programlisting>
</listitem>
<listitem>
<para>
Setup the proxy environment variables in the shell where you are
running <literal>nixos-install</literal>.
</para>
<programlisting>
# proxy_url=&quot;http://user:password@proxy:port/&quot;
# export http_proxy=&quot;$proxy_url&quot;
# export HTTP_PROXY=&quot;$proxy_url&quot;
# export https_proxy=&quot;$proxy_url&quot;
# export HTTPS_PROXY=&quot;$proxy_url&quot;
</programlisting>
</listitem>
</orderedlist>
<note>
<para>
If you are switching networks with different proxy configurations,
use the <literal>specialisation</literal> option in
<literal>configuration.nix</literal> to switch proxies at runtime.
Refer to <xref linkend="ch-options" /> for more information.
</para>
</note>
</section>

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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-installing-from-other-distro">
<title>Installing from another Linux distribution</title>
<para>
Because Nix (the package manager) &amp; Nixpkgs (the Nix packages
collection) can both be installed on any (most?) Linux
distributions, they can be used to install NixOS in various creative
ways. You can, for instance:
</para>
<orderedlist numeration="arabic">
<listitem>
<para>
Install NixOS on another partition, from your existing Linux
distribution (without the use of a USB or optical device!)
</para>
</listitem>
<listitem>
<para>
Install NixOS on the same partition (in place!), from your
existing non-NixOS Linux distribution using
<literal>NIXOS_LUSTRATE</literal>.
</para>
</listitem>
<listitem>
<para>
Install NixOS on your hard drive from the Live CD of any Linux
distribution.
</para>
</listitem>
</orderedlist>
<para>
The first steps to all these are the same:
</para>
<orderedlist numeration="arabic">
<listitem>
<para>
Install the Nix package manager:
</para>
<para>
Short version:
</para>
<programlisting>
$ curl -L https://nixos.org/nix/install | sh
$ . $HOME/.nix-profile/etc/profile.d/nix.sh # …or open a fresh shell
</programlisting>
<para>
More details in the
<link xlink:href="https://nixos.org/nix/manual/#chap-quick-start">
Nix manual</link>
</para>
</listitem>
<listitem>
<para>
Switch to the NixOS channel:
</para>
<para>
If you've just installed Nix on a non-NixOS distribution, you
will be on the <literal>nixpkgs</literal> channel by default.
</para>
<programlisting>
$ nix-channel --list
nixpkgs https://nixos.org/channels/nixpkgs-unstable
</programlisting>
<para>
As that channel gets released without running the NixOS tests,
it will be safer to use the <literal>nixos-*</literal> channels
instead:
</para>
<programlisting>
$ nix-channel --add https://nixos.org/channels/nixos-version nixpkgs
</programlisting>
<para>
You may want to throw in a
<literal>nix-channel --update</literal> for good measure.
</para>
</listitem>
<listitem>
<para>
Install the NixOS installation tools:
</para>
<para>
You'll need <literal>nixos-generate-config</literal> and
<literal>nixos-install</literal>, but this also makes some man
pages and <literal>nixos-enter</literal> available, just in case
you want to chroot into your NixOS partition. NixOS installs
these by default, but you don't have NixOS yet..
</para>
<programlisting>
$ nix-env -f '&lt;nixpkgs&gt;' -iA nixos-install-tools
</programlisting>
</listitem>
<listitem>
<note>
<para>
The following 5 steps are only for installing NixOS to another
partition. For installing NixOS in place using
<literal>NIXOS_LUSTRATE</literal>, skip ahead.
</para>
</note>
<para>
Prepare your target partition:
</para>
<para>
At this point it is time to prepare your target partition.
Please refer to the partitioning, file-system creation, and
mounting steps of <xref linkend="sec-installation" />
</para>
<para>
If you're about to install NixOS in place using
<literal>NIXOS_LUSTRATE</literal> there is nothing to do for
this step.
</para>
</listitem>
<listitem>
<para>
Generate your NixOS configuration:
</para>
<programlisting>
$ sudo `which nixos-generate-config` --root /mnt
</programlisting>
<para>
You'll probably want to edit the configuration files. Refer to
the <literal>nixos-generate-config</literal> step in
<xref linkend="sec-installation" /> for more information.
</para>
<para>
Consider setting up the NixOS bootloader to give you the ability
to boot on your existing Linux partition. For instance, if
you're using GRUB and your existing distribution is running
Ubuntu, you may want to add something like this to your
<literal>configuration.nix</literal>:
</para>
<programlisting language="bash">
boot.loader.grub.extraEntries = ''
menuentry &quot;Ubuntu&quot; {
search --set=ubuntu --fs-uuid 3cc3e652-0c1f-4800-8451-033754f68e6e
configfile &quot;($ubuntu)/boot/grub/grub.cfg&quot;
}
'';
</programlisting>
<para>
(You can find the appropriate UUID for your partition in
<literal>/dev/disk/by-uuid</literal>)
</para>
</listitem>
<listitem>
<para>
Create the <literal>nixbld</literal> group and user on your
original distribution:
</para>
<programlisting>
$ sudo groupadd -g 30000 nixbld
$ sudo useradd -u 30000 -g nixbld -G nixbld nixbld
</programlisting>
</listitem>
<listitem>
<para>
Download/build/install NixOS:
</para>
<warning>
<para>
Once you complete this step, you might no longer be able to
boot on existing systems without the help of a rescue USB
drive or similar.
</para>
</warning>
<note>
<para>
On some distributions there are separate PATHS for programs
intended only for root. In order for the installation to
succeed, you might have to use
<literal>PATH=&quot;$PATH:/usr/sbin:/sbin&quot;</literal> in
the following command.
</para>
</note>
<programlisting>
$ sudo PATH=&quot;$PATH&quot; NIX_PATH=&quot;$NIX_PATH&quot; `which nixos-install` --root /mnt
</programlisting>
<para>
Again, please refer to the <literal>nixos-install</literal> step
in <xref linkend="sec-installation" /> for more information.
</para>
<para>
That should be it for installation to another partition!
</para>
</listitem>
<listitem>
<para>
Optionally, you may want to clean up your non-NixOS
distribution:
</para>
<programlisting>
$ sudo userdel nixbld
$ sudo groupdel nixbld
</programlisting>
<para>
If you do not wish to keep the Nix package manager installed
either, run something like
<literal>sudo rm -rv ~/.nix-* /nix</literal> and remove the line
that the Nix installer added to your
<literal>~/.profile</literal>.
</para>
</listitem>
<listitem>
<note>
<para>
The following steps are only for installing NixOS in place
using <literal>NIXOS_LUSTRATE</literal>:
</para>
</note>
<para>
Generate your NixOS configuration:
</para>
<programlisting>
$ sudo `which nixos-generate-config` --root /
</programlisting>
<para>
Note that this will place the generated configuration files in
<literal>/etc/nixos</literal>. You'll probably want to edit the
configuration files. Refer to the
<literal>nixos-generate-config</literal> step in
<xref linkend="sec-installation" /> for more information.
</para>
<para>
You'll likely want to set a root password for your first boot
using the configuration files because you won't have a chance to
enter a password until after you reboot. You can initalize the
root password to an empty one with this line: (and of course
don't forget to set one once you've rebooted or to lock the
account with <literal>sudo passwd -l root</literal> if you use
<literal>sudo</literal>)
</para>
<programlisting language="bash">
users.users.root.initialHashedPassword = &quot;&quot;;
</programlisting>
</listitem>
<listitem>
<para>
Build the NixOS closure and install it in the
<literal>system</literal> profile:
</para>
<programlisting>
$ nix-env -p /nix/var/nix/profiles/system -f '&lt;nixpkgs/nixos&gt;' -I nixos-config=/etc/nixos/configuration.nix -iA system
</programlisting>
</listitem>
<listitem>
<para>
Change ownership of the <literal>/nix</literal> tree to root
(since your Nix install was probably single user):
</para>
<programlisting>
$ sudo chown -R 0:0 /nix
</programlisting>
</listitem>
<listitem>
<para>
Set up the <literal>/etc/NIXOS</literal> and
<literal>/etc/NIXOS_LUSTRATE</literal> files:
</para>
<para>
<literal>/etc/NIXOS</literal> officializes that this is now a
NixOS partition (the bootup scripts require its presence).
</para>
<para>
<literal>/etc/NIXOS_LUSTRATE</literal> tells the NixOS bootup
scripts to move <emphasis>everything</emphasis> that's in the
root partition to <literal>/old-root</literal>. This will move
your existing distribution out of the way in the very early
stages of the NixOS bootup. There are exceptions (we do need to
keep NixOS there after all), so the NixOS lustrate process will
not touch:
</para>
<itemizedlist>
<listitem>
<para>
The <literal>/nix</literal> directory
</para>
</listitem>
<listitem>
<para>
The <literal>/boot</literal> directory
</para>
</listitem>
<listitem>
<para>
Any file or directory listed in
<literal>/etc/NIXOS_LUSTRATE</literal> (one per line)
</para>
</listitem>
</itemizedlist>
<note>
<para>
Support for <literal>NIXOS_LUSTRATE</literal> was added in
NixOS 16.09. The act of &quot;lustrating&quot; refers to the
wiping of the existing distribution. Creating
<literal>/etc/NIXOS_LUSTRATE</literal> can also be used on
NixOS to remove all mutable files from your root partition
(anything that's not in <literal>/nix</literal> or
<literal>/boot</literal> gets &quot;lustrated&quot; on the
next boot.
</para>
<para>
lustrate /ˈlʌstreɪt/ verb.
</para>
<para>
purify by expiatory sacrifice, ceremonial washing, or some
other ritual action.
</para>
</note>
<para>
Let's create the files:
</para>
<programlisting>
$ sudo touch /etc/NIXOS
$ sudo touch /etc/NIXOS_LUSTRATE
</programlisting>
<para>
Let's also make sure the NixOS configuration files are kept once
we reboot on NixOS:
</para>
<programlisting>
$ echo etc/nixos | sudo tee -a /etc/NIXOS_LUSTRATE
</programlisting>
</listitem>
<listitem>
<para>
Finally, move the <literal>/boot</literal> directory of your
current distribution out of the way (the lustrate process will
take care of the rest once you reboot, but this one must be
moved out now because NixOS needs to install its own boot files:
</para>
<warning>
<para>
Once you complete this step, your current distribution will no
longer be bootable! If you didn't get all the NixOS
configuration right, especially those settings pertaining to
boot loading and root partition, NixOS may not be bootable
either. Have a USB rescue device ready in case this happens.
</para>
</warning>
<programlisting>
$ sudo mv -v /boot /boot.bak &amp;&amp;
sudo /nix/var/nix/profiles/system/bin/switch-to-configuration boot
</programlisting>
<para>
Cross your fingers, reboot, hopefully you should get a NixOS
prompt!
</para>
</listitem>
<listitem>
<para>
If for some reason you want to revert to the old distribution,
you'll need to boot on a USB rescue disk and do something along
these lines:
</para>
<programlisting>
# mkdir root
# mount /dev/sdaX root
# mkdir root/nixos-root
# mv -v root/* root/nixos-root/
# mv -v root/nixos-root/old-root/* root/
# mv -v root/boot.bak root/boot # We had renamed this by hand earlier
# umount root
# reboot
</programlisting>
<para>
This may work as is or you might also need to reinstall the boot
loader.
</para>
<para>
And of course, if you're happy with NixOS and no longer need the
old distribution:
</para>
<programlisting>
sudo rm -rf /old-root
</programlisting>
</listitem>
<listitem>
<para>
It's also worth noting that this whole process can be automated.
This is especially useful for Cloud VMs, where provider do not
provide NixOS. For instance,
<link xlink:href="https://github.com/elitak/nixos-infect">nixos-infect</link>
uses the lustrate process to convert Digital Ocean droplets to
NixOS from other distributions automatically.
</para>
</listitem>
</orderedlist>
</section>

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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-booting-from-pxe">
<title>Booting from the <quote>netboot</quote> media (PXE)</title>
<para>
Advanced users may wish to install NixOS using an existing PXE or
iPXE setup.
</para>
<para>
These instructions assume that you have an existing PXE or iPXE
infrastructure and simply want to add the NixOS installer as another
option. To build the necessary files from your current version of
nixpkgs, you can run:
</para>
<programlisting>
nix-build -A netboot.x86_64-linux '&lt;nixpkgs/nixos/release.nix&gt;'
</programlisting>
<para>
This will create a <literal>result</literal> directory containing: *
<literal>bzImage</literal> – the Linux kernel *
<literal>initrd</literal> – the initrd file *
<literal>netboot.ipxe</literal> – an example ipxe script
demonstrating the appropriate kernel command line arguments for this
image
</para>
<para>
If you’re using plain PXE, configure your boot loader to use the
<literal>bzImage</literal> and <literal>initrd</literal> files and
have it provide the same kernel command line arguments found in
<literal>netboot.ipxe</literal>.
</para>
<para>
If you’re using iPXE, depending on how your HTTP/FTP/etc. server is
configured you may be able to use <literal>netboot.ipxe</literal>
unmodified, or you may need to update the paths to the files to
match your server’s directory layout.
</para>
<para>
In the future we may begin making these files available as build
products from hydra at which point we will update this documentation
with instructions on how to obtain them either for placing on a
dedicated TFTP server or to boot them directly over the internet.
</para>
</section>

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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-booting-from-usb">
<title>Booting from a USB Drive</title>
<para>
For systems without CD drive, the NixOS live CD can be booted from a
USB stick. You can use the <literal>dd</literal> utility to write
the image: <literal>dd if=path-to-image of=/dev/sdX</literal>. Be
careful about specifying the correct drive; you can use the
<literal>lsblk</literal> command to get a list of block devices.
</para>
<note>
<title>On macOS</title>
<programlisting>
$ diskutil list
[..]
/dev/diskN (external, physical):
#: TYPE NAME SIZE IDENTIFIER
[..]
$ diskutil unmountDisk diskN
Unmount of all volumes on diskN was successful
$ sudo dd if=nix.iso of=/dev/rdiskN bs=1M
</programlisting>
<para>
Using the 'raw' <literal>rdiskN</literal> device instead of
<literal>diskN</literal> completes in minutes instead of hours.
After <literal>dd</literal> completes, a GUI dialog &quot;The disk
you inserted was not readable by this computer&quot; will pop up,
which can be ignored.
</para>
</note>
<para>
The <literal>dd</literal> utility will write the image verbatim to
the drive, making it the recommended option for both UEFI and
non-UEFI installations.
</para>
</section>

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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-instaling-virtualbox-guest">
<title>Installing in a VirtualBox guest</title>
<para>
Installing NixOS into a VirtualBox guest is convenient for users who
want to try NixOS without installing it on bare metal. If you want
to use a pre-made VirtualBox appliance, it is available at
<link xlink:href="https://nixos.org/nixos/download.html">the
downloads page</link>. If you want to set up a VirtualBox guest
manually, follow these instructions:
</para>
<orderedlist numeration="arabic">
<listitem>
<para>
Add a New Machine in VirtualBox with OS Type &quot;Linux / Other
Linux&quot;
</para>
</listitem>
<listitem>
<para>
Base Memory Size: 768 MB or higher.
</para>
</listitem>
<listitem>
<para>
New Hard Disk of 8 GB or higher.
</para>
</listitem>
<listitem>
<para>
Mount the CD-ROM with the NixOS ISO (by clicking on CD/DVD-ROM)
</para>
</listitem>
<listitem>
<para>
Click on Settings / System / Processor and enable PAE/NX
</para>
</listitem>
<listitem>
<para>
Click on Settings / System / Acceleration and enable
&quot;VT-x/AMD-V&quot; acceleration
</para>
</listitem>
<listitem>
<para>
Click on Settings / Display / Screen and select VMSVGA as
Graphics Controller
</para>
</listitem>
<listitem>
<para>
Save the settings, start the virtual machine, and continue
installation like normal
</para>
</listitem>
</orderedlist>
<para>
There are a few modifications you should make in configuration.nix.
Enable booting:
</para>
<programlisting language="bash">
boot.loader.grub.device = &quot;/dev/sda&quot;;
</programlisting>
<para>
Also remove the fsck that runs at startup. It will always fail to
run, stopping your boot until you press <literal>*</literal>.
</para>
<programlisting language="bash">
boot.initrd.checkJournalingFS = false;
</programlisting>
<para>
Shared folders can be given a name and a path in the host system in
the VirtualBox settings (Machine / Settings / Shared Folders, then
click on the &quot;Add&quot; icon). Add the following to the
<literal>/etc/nixos/configuration.nix</literal> to auto-mount them.
If you do not add <literal>&quot;nofail&quot;</literal>, the system
will not boot properly.
</para>
<programlisting language="bash">
{ config, pkgs, ...} :
{
fileSystems.&quot;/virtualboxshare&quot; = {
fsType = &quot;vboxsf&quot;;
device = &quot;nameofthesharedfolder&quot;;
options = [ &quot;rw&quot; &quot;nofail&quot; ];
};
}
</programlisting>
<para>
The folder will be available directly under the root directory.
</para>
</section>

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-installation">
<title>Installing NixOS</title>
<section xml:id="sec-installation-booting">
<title>Booting the system</title>
<para>
NixOS can be installed on BIOS or UEFI systems. The procedure for
a UEFI installation is by and large the same as a BIOS
installation. The differences are mentioned in the steps that
follow.
</para>
<para>
The installation media can be burned to a CD, or now more
commonly, <quote>burned</quote> to a USB drive (see
<xref linkend="sec-booting-from-usb" />).
</para>
<para>
The installation media contains a basic NixOS installation. When
it’s finished booting, it should have detected most of your
hardware.
</para>
<para>
The NixOS manual is available by running
<literal>nixos-help</literal>.
</para>
<para>
You are logged-in automatically as <literal>nixos</literal>. The
<literal>nixos</literal> user account has an empty password so you
can use <literal>sudo</literal> without a password:
</para>
<programlisting>
$ sudo -i
</programlisting>
<para>
If you downloaded the graphical ISO image, you can run
<literal>systemctl start display-manager</literal> to start the
desktop environment. If you want to continue on the terminal, you
can use <literal>loadkeys</literal> to switch to your preferred
keyboard layout. (We even provide neo2 via
<literal>loadkeys de neo</literal>!)
</para>
<para>
If the text is too small to be legible, try
<literal>setfont ter-v32n</literal> to increase the font size.
</para>
<para>
To install over a serial port connect with
<literal>115200n8</literal> (e.g.
<literal>picocom -b 115200 /dev/ttyUSB0</literal>). When the
bootloader lists boot entries, select the serial console boot
entry.
</para>
<section xml:id="sec-installation-booting-networking">
<title>Networking in the installer</title>
<para>
The boot process should have brought up networking (check
<literal>ip a</literal>). Networking is necessary for the
installer, since it will download lots of stuff (such as source
tarballs or Nixpkgs channel binaries). It’s best if you have a
DHCP server on your network. Otherwise configure networking
manually using <literal>ifconfig</literal>.
</para>
<para>
On the graphical installer, you can configure the network, wifi
included, through NetworkManager. Using the
<literal>nmtui</literal> program, you can do so even in a
non-graphical session. If you prefer to configure the network
manually, disable NetworkManager with
<literal>systemctl stop NetworkManager</literal>.
</para>
<para>
On the minimal installer, NetworkManager is not available, so
configuration must be perfomed manually. To configure the wifi,
first start wpa_supplicant with
<literal>sudo systemctl start wpa_supplicant</literal>, then run
<literal>wpa_cli</literal>. For most home networks, you need to
type in the following commands:
</para>
<programlisting>
&gt; add_network
0
&gt; set_network 0 ssid &quot;myhomenetwork&quot;
OK
&gt; set_network 0 psk &quot;mypassword&quot;
OK
&gt; set_network 0 key_mgmt WPA-PSK
OK
&gt; enable_network 0
OK
</programlisting>
<para>
For enterprise networks, for example
<emphasis>eduroam</emphasis>, instead do:
</para>
<programlisting>
&gt; add_network
0
&gt; set_network 0 ssid &quot;eduroam&quot;
OK
&gt; set_network 0 identity &quot;myname@example.com&quot;
OK
&gt; set_network 0 password &quot;mypassword&quot;
OK
&gt; set_network 0 key_mgmt WPA-EAP
OK
&gt; enable_network 0
OK
</programlisting>
<para>
When successfully connected, you should see a line such as this
one
</para>
<programlisting>
&lt;3&gt;CTRL-EVENT-CONNECTED - Connection to 32:85:ab:ef:24:5c completed [id=0 id_str=]
</programlisting>
<para>
you can now leave <literal>wpa_cli</literal> by typing
<literal>quit</literal>.
</para>
<para>
If you would like to continue the installation from a different
machine you can use activated SSH daemon. You need to copy your
ssh key to either
<literal>/home/nixos/.ssh/authorized_keys</literal> or
<literal>/root/.ssh/authorized_keys</literal> (Tip: For
installers with a modifiable filesystem such as the sd-card
installer image a key can be manually placed by mounting the
image on a different machine). Alternatively you must set a
password for either <literal>root</literal> or
<literal>nixos</literal> with <literal>passwd</literal> to be
able to login.
</para>
</section>
</section>
<section xml:id="sec-installation-partitioning">
<title>Partitioning and formatting</title>
<para>
The NixOS installer doesn’t do any partitioning or formatting, so
you need to do that yourself.
</para>
<para>
The NixOS installer ships with multiple partitioning tools. The
examples below use <literal>parted</literal>, but also provides
<literal>fdisk</literal>, <literal>gdisk</literal>,
<literal>cfdisk</literal>, and <literal>cgdisk</literal>.
</para>
<para>
The recommended partition scheme differs depending if the computer
uses <emphasis>Legacy Boot</emphasis> or
<emphasis>UEFI</emphasis>.
</para>
<section xml:id="sec-installation-partitioning-UEFI">
<title>UEFI (GPT)</title>
<para>
Here's an example partition scheme for UEFI, using
<literal>/dev/sda</literal> as the device.
</para>
<note>
<para>
You can safely ignore <literal>parted</literal>'s
informational message about needing to update /etc/fstab.
</para>
</note>
<orderedlist numeration="arabic">
<listitem>
<para>
Create a <emphasis>GPT</emphasis> partition table.
</para>
<programlisting>
# parted /dev/sda -- mklabel gpt
</programlisting>
</listitem>
<listitem>
<para>
Add the <emphasis>root</emphasis> partition. This will fill
the disk except for the end part, where the swap will live,
and the space left in front (512MiB) which will be used by
the boot partition.
</para>
<programlisting>
# parted /dev/sda -- mkpart primary 512MiB -8GiB
</programlisting>
</listitem>
<listitem>
<para>
Next, add a <emphasis>swap</emphasis> partition. The size
required will vary according to needs, here a 8GiB one is
created.
</para>
<programlisting>
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
<note>
<para>
The swap partition size rules are no different than for
other Linux distributions.
</para>
</note>
</listitem>
<listitem>
<para>
Finally, the <emphasis>boot</emphasis> partition. NixOS by
default uses the ESP (EFI system partition) as its
<emphasis>/boot</emphasis> partition. It uses the initially
reserved 512MiB at the start of the disk.
</para>
<programlisting>
# parted /dev/sda -- mkpart ESP fat32 1MiB 512MiB
# parted /dev/sda -- set 3 esp on
</programlisting>
</listitem>
</orderedlist>
<para>
Once complete, you can follow with
<xref linkend="sec-installation-partitioning-formatting" />.
</para>
</section>
<section xml:id="sec-installation-partitioning-MBR">
<title>Legacy Boot (MBR)</title>
<para>
Here's an example partition scheme for Legacy Boot, using
<literal>/dev/sda</literal> as the device.
</para>
<note>
<para>
You can safely ignore <literal>parted</literal>'s
informational message about needing to update /etc/fstab.
</para>
</note>
<orderedlist numeration="arabic">
<listitem>
<para>
Create a <emphasis>MBR</emphasis> partition table.
</para>
<programlisting>
# parted /dev/sda -- mklabel msdos
</programlisting>
</listitem>
<listitem>
<para>
Add the <emphasis>root</emphasis> partition. This will fill
the the disk except for the end part, where the swap will
live.
</para>
<programlisting>
# parted /dev/sda -- mkpart primary 1MiB -8GiB
</programlisting>
</listitem>
<listitem>
<para>
Finally, add a <emphasis>swap</emphasis> partition. The size
required will vary according to needs, here a 8GiB one is
created.
</para>
<programlisting>
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
<note>
<para>
The swap partition size rules are no different than for
other Linux distributions.
</para>
</note>
</listitem>
</orderedlist>
<para>
Once complete, you can follow with
<xref linkend="sec-installation-partitioning-formatting" />.
</para>
</section>
<section xml:id="sec-installation-partitioning-formatting">
<title>Formatting</title>
<para>
Use the following commands:
</para>
<itemizedlist>
<listitem>
<para>
For initialising Ext4 partitions:
<literal>mkfs.ext4</literal>. It is recommended that you
assign a unique symbolic label to the file system using the
option <literal>-L label</literal>, since this makes the
file system configuration independent from device changes.
For example:
</para>
<programlisting>
# mkfs.ext4 -L nixos /dev/sda1
</programlisting>
</listitem>
<listitem>
<para>
For creating swap partitions: <literal>mkswap</literal>.
Again it’s recommended to assign a label to the swap
partition: <literal>-L label</literal>. For example:
</para>
<programlisting>
# mkswap -L swap /dev/sda2
</programlisting>
</listitem>
<listitem>
<para>
<emphasis role="strong">UEFI systems</emphasis>
</para>
<para>
For creating boot partitions: <literal>mkfs.fat</literal>.
Again it’s recommended to assign a label to the boot
partition: <literal>-n label</literal>. For example:
</para>
<programlisting>
# mkfs.fat -F 32 -n boot /dev/sda3
</programlisting>
</listitem>
<listitem>
<para>
For creating LVM volumes, the LVM commands, e.g.,
<literal>pvcreate</literal>, <literal>vgcreate</literal>,
and <literal>lvcreate</literal>.
</para>
</listitem>
<listitem>
<para>
For creating software RAID devices, use
<literal>mdadm</literal>.
</para>
</listitem>
</itemizedlist>
</section>
</section>
<section xml:id="sec-installation-installing">
<title>Installing</title>
<orderedlist numeration="arabic">
<listitem>
<para>
Mount the target file system on which NixOS should be
installed on <literal>/mnt</literal>, e.g.
</para>
<programlisting>
# mount /dev/disk/by-label/nixos /mnt
</programlisting>
</listitem>
<listitem>
<para>
<emphasis role="strong">UEFI systems</emphasis>
</para>
<para>
Mount the boot file system on <literal>/mnt/boot</literal>,
e.g.
</para>
<programlisting>
# mkdir -p /mnt/boot
# mount /dev/disk/by-label/boot /mnt/boot
</programlisting>
</listitem>
<listitem>
<para>
If your machine has a limited amount of memory, you may want
to activate swap devices now
(<literal>swapon device</literal>). The installer (or rather,
the build actions that it may spawn) may need quite a bit of
RAM, depending on your configuration.
</para>
<programlisting>
# swapon /dev/sda2
</programlisting>
</listitem>
<listitem>
<para>
You now need to create a file
<literal>/mnt/etc/nixos/configuration.nix</literal> that
specifies the intended configuration of the system. This is
because NixOS has a <emphasis>declarative</emphasis>
configuration model: you create or edit a description of the
desired configuration of your system, and then NixOS takes
care of making it happen. The syntax of the NixOS
configuration file is described in
<xref linkend="sec-configuration-syntax" />, while a list of
available configuration options appears in
<xref linkend="ch-options" />. A minimal example is shown in
<link linkend="ex-config">Example: NixOS Configuration</link>.
</para>
<para>
The command <literal>nixos-generate-config</literal> can
generate an initial configuration file for you:
</para>
<programlisting>
# nixos-generate-config --root /mnt
</programlisting>
<para>
You should then edit
<literal>/mnt/etc/nixos/configuration.nix</literal> to suit
your needs:
</para>
<programlisting>
# nano /mnt/etc/nixos/configuration.nix
</programlisting>
<para>
If you’re using the graphical ISO image, other editors may be
available (such as <literal>vim</literal>). If you have
network access, you can also install other editors – for
instance, you can install Emacs by running
<literal>nix-env -f '&lt;nixpkgs&gt;' -iA emacs</literal>.
</para>
<variablelist>
<varlistentry>
<term>
BIOS systems
</term>
<listitem>
<para>
You <emphasis>must</emphasis> set the option
<xref linkend="opt-boot.loader.grub.device" /> to
specify on which disk the GRUB boot loader is to be
installed. Without it, NixOS cannot boot.
</para>
<para>
If there are other operating systems running on the
machine before installing NixOS, the
<xref linkend="opt-boot.loader.grub.useOSProber" />
option can be set to <literal>true</literal> to
automatically add them to the grub menu.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
UEFI systems
</term>
<listitem>
<para>
You <emphasis>must</emphasis> set the option
<xref linkend="opt-boot.loader.systemd-boot.enable" />
to <literal>true</literal>.
<literal>nixos-generate-config</literal> should do this
automatically for new configurations when booted in UEFI
mode.
</para>
<para>
You may want to look at the options starting with
<link linkend="opt-boot.loader.efi.canTouchEfiVariables"><literal>boot.loader.efi</literal></link>
and
<link linkend="opt-boot.loader.systemd-boot.enable"><literal>boot.loader.systemd-boot</literal></link>
as well.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
If you need to configure networking for your machine the
configuration options are described in
<xref linkend="sec-networking" />. In particular, while wifi
is supported on the installation image, it is not enabled by
default in the configuration generated by
<literal>nixos-generate-config</literal>.
</para>
<para>
Another critical option is <literal>fileSystems</literal>,
specifying the file systems that need to be mounted by NixOS.
However, you typically don’t need to set it yourself, because
<literal>nixos-generate-config</literal> sets it automatically
in
<literal>/mnt/etc/nixos/hardware-configuration.nix</literal>
from your currently mounted file systems. (The configuration
file <literal>hardware-configuration.nix</literal> is included
from <literal>configuration.nix</literal> and will be
overwritten by future invocations of
<literal>nixos-generate-config</literal>; thus, you generally
should not modify it.) Additionally, you may want to look at
<link xlink:href="https://github.com/NixOS/nixos-hardware">Hardware
configuration for known-hardware</link> at this point or after
installation.
</para>
<note>
<para>
Depending on your hardware configuration or type of file
system, you may need to set the option
<literal>boot.initrd.kernelModules</literal> to include the
kernel modules that are necessary for mounting the root file
system, otherwise the installed system will not be able to
boot. (If this happens, boot from the installation media
again, mount the target file system on
<literal>/mnt</literal>, fix
<literal>/mnt/etc/nixos/configuration.nix</literal> and
rerun <literal>nixos-install</literal>.) In most cases,
<literal>nixos-generate-config</literal> will figure out the
required modules.
</para>
</note>
</listitem>
<listitem>
<para>
Do the installation:
</para>
<programlisting>
# nixos-install
</programlisting>
<para>
This will install your system based on the configuration you
provided. If anything fails due to a configuration problem or
any other issue (such as a network outage while downloading
binaries from the NixOS binary cache), you can re-run
<literal>nixos-install</literal> after fixing your
<literal>configuration.nix</literal>.
</para>
<para>
As the last step, <literal>nixos-install</literal> will ask
you to set the password for the <literal>root</literal> user,
e.g.
</para>
<programlisting>
setting root password...
New password: ***
Retype new password: ***
</programlisting>
<note>
<para>
For unattended installations, it is possible to use
<literal>nixos-install --no-root-passwd</literal> in order
to disable the password prompt entirely.
</para>
</note>
</listitem>
<listitem>
<para>
If everything went well:
</para>
<programlisting>
# reboot
</programlisting>
</listitem>
<listitem>
<para>
You should now be able to boot into the installed NixOS. The
GRUB boot menu shows a list of <emphasis>available
configurations</emphasis> (initially just one). Every time you
change the NixOS configuration (see
<link linkend="sec-changing-config">Changing
Configuration</link>), a new item is added to the menu. This
allows you to easily roll back to a previous configuration if
something goes wrong.
</para>
<para>
You should log in and change the <literal>root</literal>
password with <literal>passwd</literal>.
</para>
<para>
You’ll probably want to create some user accounts as well,
which can be done with <literal>useradd</literal>:
</para>
<programlisting>
$ useradd -c 'Eelco Dolstra' -m eelco
$ passwd eelco
</programlisting>
<para>
You may also want to install some software. This will be
covered in <xref linkend="sec-package-management" />.
</para>
</listitem>
</orderedlist>
</section>
<section xml:id="sec-installation-summary">
<title>Installation summary</title>
<para>
To summarise, <link linkend="ex-install-sequence">Example:
Commands for Installing NixOS on
<literal>/dev/sda</literal></link> shows a typical sequence of
commands for installing NixOS on an empty hard drive (here
<literal>/dev/sda</literal>). <link linkend="ex-config">Example:
NixOS Configuration</link> shows a corresponding configuration Nix
expression.
</para>
<anchor xml:id="ex-partition-scheme-MBR" />
<para>
<emphasis role="strong">Example: Example partition schemes for
NixOS on <literal>/dev/sda</literal> (MBR)</emphasis>
</para>
<programlisting>
# parted /dev/sda -- mklabel msdos
# parted /dev/sda -- mkpart primary 1MiB -8GiB
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
</programlisting>
<anchor xml:id="ex-partition-scheme-UEFI" />
<para>
<emphasis role="strong">Example: Example partition schemes for
NixOS on <literal>/dev/sda</literal> (UEFI)</emphasis>
</para>
<programlisting>
# parted /dev/sda -- mklabel gpt
# parted /dev/sda -- mkpart primary 512MiB -8GiB
# parted /dev/sda -- mkpart primary linux-swap -8GiB 100%
# parted /dev/sda -- mkpart ESP fat32 1MiB 512MiB
# parted /dev/sda -- set 3 esp on
</programlisting>
<anchor xml:id="ex-install-sequence" />
<para>
<emphasis role="strong">Example: Commands for Installing NixOS on
<literal>/dev/sda</literal></emphasis>
</para>
<para>
With a partitioned disk.
</para>
<programlisting>
# mkfs.ext4 -L nixos /dev/sda1
# mkswap -L swap /dev/sda2
# swapon /dev/sda2
# mkfs.fat -F 32 -n boot /dev/sda3 # (for UEFI systems only)
# mount /dev/disk/by-label/nixos /mnt
# mkdir -p /mnt/boot # (for UEFI systems only)
# mount /dev/disk/by-label/boot /mnt/boot # (for UEFI systems only)
# nixos-generate-config --root /mnt
# nano /mnt/etc/nixos/configuration.nix
# nixos-install
# reboot
</programlisting>
<anchor xml:id="ex-config" />
<para>
<emphasis role="strong">Example: NixOS Configuration</emphasis>
</para>
<programlisting>
{ config, pkgs, ... }: {
imports = [
# Include the results of the hardware scan.
./hardware-configuration.nix
];
boot.loader.grub.device = &quot;/dev/sda&quot;; # (for BIOS systems only)
boot.loader.systemd-boot.enable = true; # (for UEFI systems only)
# Note: setting fileSystems is generally not
# necessary, since nixos-generate-config figures them out
# automatically in hardware-configuration.nix.
#fileSystems.&quot;/&quot;.device = &quot;/dev/disk/by-label/nixos&quot;;
# Enable the OpenSSH server.
services.sshd.enable = true;
}
</programlisting>
</section>
<section xml:id="sec-installation-additional-notes">
<title>Additional installation notes</title>
<xi:include href="installing-usb.section.xml" />
<xi:include href="installing-pxe.section.xml" />
<xi:include href="installing-virtualbox-guest.section.xml" />
<xi:include href="installing-from-other-distro.section.xml" />
<xi:include href="installing-behind-a-proxy.section.xml" />
</section>
</chapter>

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-obtaining">
<title>Obtaining NixOS</title>
<para>
NixOS ISO images can be downloaded from the
<link xlink:href="https://nixos.org/nixos/download.html">NixOS
download page</link>. There are a number of installation options. If
you happen to have an optical drive and a spare CD, burning the
image to CD and booting from that is probably the easiest option.
Most people will need to prepare a USB stick to boot from.
<xref linkend="sec-booting-from-usb" /> describes the preferred
method to prepare a USB stick. A number of alternative methods are
presented in the
<link xlink:href="https://nixos.wiki/wiki/NixOS_Installation_Guide#Making_the_installation_media">NixOS
Wiki</link>.
</para>
<para>
As an alternative to installing NixOS yourself, you can get a
running NixOS system through several other means:
</para>
<itemizedlist>
<listitem>
<para>
Using virtual appliances in Open Virtualization Format (OVF)
that can be imported into VirtualBox. These are available from
the
<link xlink:href="https://nixos.org/nixos/download.html">NixOS
download page</link>.
</para>
</listitem>
<listitem>
<para>
Using AMIs for Amazon’s EC2. To find one for your region and
instance type, please refer to the
<link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/virtualisation/ec2-amis.nix">list
of most recent AMIs</link>.
</para>
</listitem>
<listitem>
<para>
Using NixOps, the NixOS-based cloud deployment tool, which
allows you to provision VirtualBox and EC2 NixOS instances from
declarative specifications. Check out the
<link xlink:href="https://nixos.org/nixops">NixOps
homepage</link> for details.
</para>
</listitem>
</itemizedlist>
</chapter>

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-upgrading">
<title>Upgrading NixOS</title>
<para>
The best way to keep your NixOS installation up to date is to use
one of the NixOS <emphasis>channels</emphasis>. A channel is a Nix
mechanism for distributing Nix expressions and associated binaries.
The NixOS channels are updated automatically from NixOS’s Git
repository after certain tests have passed and all packages have
been built. These channels are:
</para>
<itemizedlist>
<listitem>
<para>
<emphasis>Stable channels</emphasis>, such as
<link xlink:href="https://nixos.org/channels/nixos-22.05"><literal>nixos-22.05</literal></link>.
These only get conservative bug fixes and package upgrades. For
instance, a channel update may cause the Linux kernel on your
system to be upgraded from 4.19.34 to 4.19.38 (a minor bug fix),
but not from 4.19.x to 4.20.x (a major change that has the
potential to break things). Stable channels are generally
maintained until the next stable branch is created.
</para>
</listitem>
<listitem>
<para>
The <emphasis>unstable channel</emphasis>,
<link xlink:href="https://nixos.org/channels/nixos-unstable"><literal>nixos-unstable</literal></link>.
This corresponds to NixOS’s main development branch, and may
thus see radical changes between channel updates. It’s not
recommended for production systems.
</para>
</listitem>
<listitem>
<para>
<emphasis>Small channels</emphasis>, such as
<link xlink:href="https://nixos.org/channels/nixos-22.05-small"><literal>nixos-22.05-small</literal></link>
or
<link xlink:href="https://nixos.org/channels/nixos-unstable-small"><literal>nixos-unstable-small</literal></link>.
These are identical to the stable and unstable channels
described above, except that they contain fewer binary packages.
This means they get updated faster than the regular channels
(for instance, when a critical security patch is committed to
NixOS’s source tree), but may require more packages to be built
from source than usual. They’re mostly intended for server
environments and as such contain few GUI applications.
</para>
</listitem>
</itemizedlist>
<para>
To see what channels are available, go to
<link xlink:href="https://nixos.org/channels">https://nixos.org/channels</link>.
(Note that the URIs of the various channels redirect to a directory
that contains the channel’s latest version and includes ISO images
and VirtualBox appliances.) Please note that during the release
process, channels that are not yet released will be present here as
well. See the Getting NixOS page
<link xlink:href="https://nixos.org/nixos/download.html">https://nixos.org/nixos/download.html</link>
to find the newest supported stable release.
</para>
<para>
When you first install NixOS, you’re automatically subscribed to the
NixOS channel that corresponds to your installation source. For
instance, if you installed from a 22.05 ISO, you will be subscribed
to the <literal>nixos-22.05</literal> channel. To see which NixOS
channel you’re subscribed to, run the following as root:
</para>
<programlisting>
# nix-channel --list | grep nixos
nixos https://nixos.org/channels/nixos-unstable
</programlisting>
<para>
To switch to a different NixOS channel, do
</para>
<programlisting>
# nix-channel --add https://nixos.org/channels/channel-name nixos
</programlisting>
<para>
(Be sure to include the <literal>nixos</literal> parameter at the
end.) For instance, to use the NixOS 22.05 stable channel:
</para>
<programlisting>
# nix-channel --add https://nixos.org/channels/nixos-22.05 nixos
</programlisting>
<para>
If you have a server, you may want to use the <quote>small</quote>
channel instead:
</para>
<programlisting>
# nix-channel --add https://nixos.org/channels/nixos-22.05-small nixos
</programlisting>
<para>
And if you want to live on the bleeding edge:
</para>
<programlisting>
# nix-channel --add https://nixos.org/channels/nixos-unstable nixos
</programlisting>
<para>
You can then upgrade NixOS to the latest version in your chosen
channel by running
</para>
<programlisting>
# nixos-rebuild switch --upgrade
</programlisting>
<para>
which is equivalent to the more verbose
<literal>nix-channel --update nixos; nixos-rebuild switch</literal>.
</para>
<note>
<para>
Channels are set per user. This means that running
<literal>nix-channel --add</literal> as a non root user (or
without sudo) will not affect configuration in
<literal>/etc/nixos/configuration.nix</literal>
</para>
</note>
<warning>
<para>
It is generally safe to switch back and forth between channels.
The only exception is that a newer NixOS may also have a newer Nix
version, which may involve an upgrade of Nix’s database schema.
This cannot be undone easily, so in that case you will not be able
to go back to your original channel.
</para>
</warning>
<section xml:id="sec-upgrading-automatic">
<title>Automatic Upgrades</title>
<para>
You can keep a NixOS system up-to-date automatically by adding the
following to <literal>configuration.nix</literal>:
</para>
<programlisting language="bash">
system.autoUpgrade.enable = true;
system.autoUpgrade.allowReboot = true;
</programlisting>
<para>
This enables a periodically executed systemd service named
<literal>nixos-upgrade.service</literal>. If the
<literal>allowReboot</literal> option is <literal>false</literal>,
it runs <literal>nixos-rebuild switch --upgrade</literal> to
upgrade NixOS to the latest version in the current channel. (To
see when the service runs, see
<literal>systemctl list-timers</literal>.) If
<literal>allowReboot</literal> is <literal>true</literal>, then
the system will automatically reboot if the new generation
contains a different kernel, initrd or kernel modules. You can
also specify a channel explicitly, e.g.
</para>
<programlisting language="bash">
system.autoUpgrade.channel = https://nixos.org/channels/nixos-22.05;
</programlisting>
</section>
</chapter>