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doc: Add “Getting Started with the System” section.

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* doc/guix.texi (Getting Started with the System): New node.
(After System Installation): Refer to it.  Move note about ‘sudo guix
pull’ to the “Getting Started with the System”.
(Getting Started): Refer to it.  Move note about ‘guix system roll-back’
to “Getting Started with the System”.
(Features): Refer to it.
(Using the Configuration System): Adjust intro.  Add “Troubleshooting”
note that mentions ‘guix style -f’ for misplaced parens.
(Instantiating the System): Simplify and cross-reference “Getting
Started with the System”.

Change-Id: Ie74f598450e8059a4579a016e2aeca2edd7696a7
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Ludovic Courtès 2024-02-21 15:45:15 +01:00
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@ -358,6 +358,7 @@ Foreign Architectures
System Configuration
* Getting Started with the System:: Your first steps.
* Using the Configuration System:: Customizing your GNU system.
* operating-system Reference:: Detail of operating-system declarations.
* File Systems:: Configuring file system mounts.
@ -2879,8 +2880,8 @@ unless your configuration specifies otherwise
@node After System Installation
@section After System Installation
Success, you've now booted into Guix System! From then on, you can update the
system whenever you want by running, say:
Success, you've now booted into Guix System! You can upgrade the system
whenever you want by running:
@example
guix pull
@ -2888,24 +2889,10 @@ sudo guix system reconfigure /etc/config.scm
@end example
@noindent
This builds a new system generation with the latest packages and services
(@pxref{Invoking guix system}). We recommend doing that regularly so that
your system includes the latest security updates (@pxref{Security Updates}).
This builds a new system @dfn{generation} with the latest packages and
services.
@c See <https://lists.gnu.org/archive/html/guix-devel/2019-01/msg00268.html>.
@quotation Note
@cindex sudo vs. @command{guix pull}
Note that @command{sudo guix} runs your user's @command{guix} command and
@emph{not} root's, because @command{sudo} leaves @env{PATH} unchanged. To
explicitly run root's @command{guix}, type @command{sudo -i guix @dots{}}.
The difference matters here, because @command{guix pull} updates
the @command{guix} command and package definitions only for the user it is run
as. This means that if you choose to use @command{guix system reconfigure} in
root's login shell, you'll need to @command{guix pull} separately.
@end quotation
Now, @pxref{Getting Started}, and
Now, @pxref{Getting Started with the System}, and
join us on @code{#guix} on the Libera Chat IRC network or on
@email{guix-devel@@gnu.org} to share your experience!
@ -3159,22 +3146,9 @@ sudo guix system reconfigure /etc/config.scm
@end example
Upon completion, the system runs the latest versions of its software
packages. When you eventually reboot, you'll notice a sub-menu in the
bootloader that reads ``Old system generations'': it's what allows you
to boot @emph{an older generation of your system}, should the latest
generation be ``broken'' or otherwise unsatisfying. Just like for
packages, you can always @emph{roll back} to a previous generation
@emph{of the whole system}:
@example
sudo guix system roll-back
@end example
There are many things you'll probably want to tweak on your system:
adding new user accounts, adding new system services, fiddling with the
configuration of those services, etc. The system configuration is
@emph{entirely} described in the @file{/etc/config.scm} file.
@xref{Using the Configuration System}, to learn how to change it.
packages. Just like for packages, you can always @emph{roll back} to a
previous generation @emph{of the whole system}. @xref{Getting Started
with the System}, to learn how to manage your system.
Now you know enough to get started!
@ -3283,7 +3257,7 @@ out to have a serious bug, users may roll back to the previous instance
of their profile, which was known to work well. Similarly, the global
system configuration on Guix is subject to
transactional upgrades and roll-back
(@pxref{Using the Configuration System}).
(@pxref{Getting Started with the System}).
All packages in the package store may be @emph{garbage-collected}.
Guix can determine which packages are still referenced by user
@ -17101,6 +17075,7 @@ instantiated. Then we show how this mechanism can be extended, for
instance to support new system services.
@menu
* Getting Started with the System:: Your first steps.
* Using the Configuration System:: Customizing your GNU system.
* operating-system Reference:: Detail of operating-system declarations.
* File Systems:: Configuring file system mounts.
@ -17121,14 +17096,222 @@ instance to support new system services.
* Defining Services:: Adding new service definitions.
@end menu
@node Getting Started with the System
@section Getting Started
@cindex system configuration file
@cindex configuration file, of the system
You're reading this section probably because you have just installed
Guix System (@pxref{System Installation}) and would like to know where
to go from here. If you're already familiar with GNU/Linux system
administration, the way Guix System is configured is very different from
what you're used to: you won't install a system service by running
@command{guix install}, you won't configure services by modifying files
under @file{/etc}, and you won't create user accounts by invoking
@command{useradd}; instead, all these aspects are spelled out in a
@dfn{system configuration file}.
The first step with Guix System is thus to write the @dfn{system
configuration file}; luckily, system installation already generated one
for you and stored it under @file{/etc/config.scm}.
@quotation Note
You can store your system configuration file anywhere you like---it
doesn't have to be at @file{/etc/config.scm}. It's a good idea to keep
it under version control, for instance in a
@uref{https://git-scm.com/book/en/, Git repository}.
@end quotation
The @emph{entire} configuration of the system---user accounts, system
services, timezone, locale settings---is declared in this file, which
follows this template:
@lisp
(use-modules (gnu))
(use-package-modules @dots{})
(use-service-modules @dots{})
(operating-system
(host-name @dots{})
(timezone @dots{})
(locale @dots{})
(bootloader @dots{})
(file-systems @dots{})
(users @dots{})
(packages @dots{})
(services @dots{}))
@end lisp
This configuration file is in fact a Scheme program; the first lines
pull in modules providing variables you might need in the rest of the
file---e.g., packages, services, etc. The @code{operating-system} form
declares the system configuration as a @dfn{record} with a number of
@dfn{fields}. @xref{Using the Configuration System}, to view complete
examples and learn what to put in there.
The second step, once you have this configuration file, is to test it.
Of course, you can skip this step if you're feeling lucky---you choose!
To do that, pass your configuration file to @command{guix system vm} (no
need to be root, you can do that as a regular user):
@example
guix system vm /etc/config.scm
@end example
@noindent
This command returns the name of a shell script that starts a virtual
machine (VM) running the system @emph{as described in the configuration
file}:
@example
/gnu/store/@dots{}-run-vm.sh
@end example
@noindent
In this VM, you can log in as @code{root} with no password. That's a
good way to check that your configuration file is correct and that it
gives the expected result, without touching your system. @xref{Invoking
guix system}, for more information.
@quotation Note
When using @command{guix system vm}, aspects tied to your hardware such
as file systems and mapped devices are overridden because they cannot be
meaningfully tested in the VM@. Other aspects such as static network
configuration (@pxref{Networking Setup,
@code{static-networking-service-type}}) are @emph{not} overridden but
they may not work inside the VM@.
@end quotation
@cindex system instantiation
@cindex reconfiguring the system
The third step, once you're happy with your configuration, is to
@dfn{instantiate} it---make this configuration effective on your system.
To do that, run:
@example
sudo guix system reconfigure /etc/config.scm
@end example
@cindex upgrading system services
@cindex system services, upgrading
@noindent
This operation is @dfn{transactional}: either it succeeds and you end up
with an upgraded system, or it fails and nothing has changed. Note that
it does @emph{not} restart system services that were already running.
Thus, to upgrade those services, you have to reboot or to explicitly
restart them; for example, to restart the secure shell (SSH) daemon, you
would run:
@example
sudo herd restart sshd
@end example
@quotation Note
System services are managed by the Shepherd (@pxref{Jump Start,,,
shepherd, The GNU Shepherd Manual}). The @code{herd} command lets you
inspect, start, and stop services. To view the status of services, run:
@example
sudo herd status
@end example
To view detailed information about a given service, add its name to the
command:
@example
sudo herd status sshd
@end example
@xref{Services}, for more information.
@end quotation
@cindex provenance, of the system
The system records its @dfn{provenance}---the configuration file and
channels that were used to deploy it. You can view it like so:
@example
guix system describe
@end example
Additionally, @command{guix system reconfigure} preserves previous
system generations, which you can list:
@example
guix system list-generations
@end example
@noindent
@cindex roll back, for the system
Crucially, that means that you can always @emph{roll back} to an earlier
generation should something go wrong! When you eventually reboot,
you'll notice a sub-menu in the bootloader that reads ``Old system
generations'': it's what allows you to boot @emph{an older generation of
your system}, should the latest generation be ``broken'' or otherwise
unsatisfying. You can also ``permanently'' roll back, like so:
@example
sudo guix system roll-back
@end example
@noindent
Alternatively, you can use @command{guix system switch-generation} to
switch to a specific generation.
Once in a while, you'll want to delete old generations that you do not
need anymore to allow @dfn{garbage collection} to free space
(@pxref{Invoking guix gc}). For example, to remove generations older
than 4 months, run:
@example
sudo guix system delete-generations 4m
@end example
From there on, anytime you want to change something in the system
configuration, be it adding a user account or changing parameters of a
service, you will first update your configuration file and then run
@command{guix system reconfigure} as shown above.
@cindex upgrade, of the system
Likewise, to @emph{upgrade} system software, you first fetch an
up-to-date Guix and then reconfigure your system with that new Guix:
@example
guix pull
sudo guix system reconfigure /etc/config.scm
@end example
@noindent
We recommend doing that regularly so that your system includes the
latest security updates (@pxref{Security Updates}).
@c See <https://lists.gnu.org/archive/html/guix-devel/2019-01/msg00268.html>.
@quotation Note
@cindex sudo vs. @command{guix pull}
@command{sudo guix} runs your user's @command{guix} command and
@emph{not} root's, because @command{sudo} leaves @env{PATH} unchanged.
The difference matters here, because @command{guix pull} updates
the @command{guix} command and package definitions only for the user it is run
as. This means that if you choose to use @command{guix system reconfigure} in
root's login shell, you'll need to @command{guix pull} separately.
@end quotation
That's it! If you're getting starting with Guix entirely,
@pxref{Getting Started}. The next sections dive in more detail into the
crux of the matter: system configuration.
@node Using the Configuration System
@section Using the Configuration System
The previous section showed the overall workflow you would follow when
administering a Guix System machine (@pxref{Getting Started with the
System}). Let's now see in more detail what goes into the system
configuration file.
The operating system is configured by providing an
@code{operating-system} declaration in a file that can then be passed to
the @command{guix system} command (@pxref{Invoking guix system}). A
simple setup, with the default Linux-Libre
kernel, initial RAM disk, and a couple of system services added to those
the @command{guix system} command (@pxref{Invoking guix system}), as
we've seen before. A simple setup, with the default Linux-Libre kernel,
initial RAM disk, and a couple of system services added to those
provided by default looks like this:
@findex operating-system
@ -17136,8 +17319,8 @@ provided by default looks like this:
@include os-config-bare-bones.texi
@end lisp
The configuration is declarative and hopefully mostly self-describing.
It is actually code in the Scheme programming language; the whole
The configuration is declarative.
It is code in the Scheme programming language; the whole
@code{(operating-system @dots{})} expression produces a @dfn{record}
with a number of @dfn{fields}.
Some of the fields defined
@ -17146,16 +17329,21 @@ Others, such as @code{packages} and @code{services}, can be omitted, in
which case they get a default value. @xref{operating-system Reference},
for details about all the available fields.
Below we discuss the effect of some of the most important fields,
and how to @dfn{instantiate} the operating system using
@command{guix system}.
Below we discuss the meaning of some of the most important fields.
@quotation Do not panic
@cindex Scheme programming language, getting started
Intimidated by the Scheme language or curious about it? The Cookbook
has a short section to get started that explains the fundamentals, which
you will find helpful when hacking your configuration. @xref{A Scheme
Crash Course,,, guix-cookbook, GNU Guix Cookbook}.
@quotation Troubleshooting
The configuration file is a Scheme program and you might get the syntax
or semantics wrong as you get started. Syntactic issues such as
misplaced parentheses can often be identified by reformatting your file:
@example
guix style -f config.scm
@end example
The Cookbook has a short section to get started with the Scheme
programming language that explains the fundamentals, which you will find
helpful when hacking your configuration. @xref{A Scheme Crash Course,,,
guix-cookbook, GNU Guix Cookbook}.
@end quotation
@unnumberedsubsec Bootloader
@ -17350,16 +17538,13 @@ Alternatively, the @code{modify-services} macro can be used:
@unnumberedsubsec Instantiating the System
@cindex system instantiation
@cindex reconfiguring the system
Assuming the @code{operating-system} declaration
is stored in the @file{my-system-config.scm}
file, the @command{guix system reconfigure my-system-config.scm} command
instantiates that configuration, and makes it the default GRUB boot
entry (@pxref{Invoking guix system}).
@quotation Note
We recommend that you keep this @file{my-system-config.scm} file safe
and under version control to easily track changes to your configuration.
@end quotation
is stored in the @file{config.scm}
file, the @command{sudo guix system reconfigure config.scm} command
instantiates that configuration, and makes it the default boot
entry. @xref{Getting Started with the System}, for an overview.
The normal way to change the system configuration is by updating this
file and re-running @command{guix system reconfigure}. One should never
@ -17369,23 +17554,6 @@ fact, you must avoid that since that would not only void your warranty
but also prevent you from rolling back to previous versions of your
system, should you ever need to.
@cindex roll-back, of the operating system
Speaking of roll-back, each time you run @command{guix system
reconfigure}, a new @dfn{generation} of the system is created---without
modifying or deleting previous generations. Old system generations get
an entry in the bootloader boot menu, allowing you to boot them in case
something went wrong with the latest generation. Reassuring, no? The
@command{guix system list-generations} command lists the system
generations available on disk. It is also possible to roll back the
system via the commands @command{guix system roll-back} and
@command{guix system switch-generation}.
Although the @command{guix system reconfigure} command will not modify
previous generations, you must take care when the current generation is not
the latest (e.g., after invoking @command{guix system roll-back}), since
the operation might overwrite a later generation (@pxref{Invoking guix
system}).
@unnumberedsubsec The Programming Interface
At the Scheme level, the bulk of an @code{operating-system} declaration