The operating system is configured by providing an
operating-system declaration in a file that can then be passed to
guix system command (see Invoking guix system). A
simple setup, with the default system services, the default Linux-Libre
kernel, initial RAM disk, and boot loader looks like this:
;; This is an operating system configuration template ;; for a "bare bones" setup, with no X11 display server. (use-modules (gnu)) (use-service-modules networking ssh) (use-package-modules admin) (operating-system (host-name "komputilo") (timezone "Europe/Berlin") (locale "en_US.UTF-8") ;; Assuming /dev/sdX is the target hard disk, and "root" is ;; the label of the target root file system. (bootloader (grub-configuration (device "/dev/sdX"))) (file-systems (cons (file-system (device "root") (title 'label) (mount-point "/") (type "ext4")) %base-file-systems)) ;; This is where user accounts are specified. The "root" ;; account is implicit, and is initially created with the ;; empty password. (users (cons (user-account (name "alice") (comment "Bob's sister") (group "users") ;; Adding the account to the "wheel" group ;; makes it a sudoer. Adding it to "audio" ;; and "video" allows the user to play sound ;; and access the webcam. (supplementary-groups '("wheel" "audio" "video")) (home-directory "/home/alice")) %base-user-accounts)) ;; Globally-installed packages. (packages (cons tcpdump %base-packages)) ;; Add services to the baseline: a DHCP client and ;; an SSH server. (services (cons* (dhcp-client-service) (lsh-service #:port-number 2222) %base-services)))
This example should be self-describing. Some of the fields defined
above, such as
bootloader, are mandatory.
Others, such as
services, can be omitted, in
which case they get a default value.
packages field lists
packages that will be globally visible on the system, for all user
accounts—i.e., in every user’s
PATH environment variable—in
addition to the per-user profiles (see Invoking guix package). The
%base-packages variable provides all the tools one would expect
for basic user and administrator tasks—including the GNU Core
Utilities, the GNU Networking Utilities, the GNU Zile lightweight text
grep, etc. The example above adds
tcpdump to those, taken from the
(gnu packages admin) module
(see Package Modules).
services field lists system services to be made
available when the system starts (see Services).
operating-system declaration above specifies that, in
addition to the basic services, we want the
lshd secure shell
daemon listening on port 2222 (see
lsh-service). Under the hood,
lsh-service arranges so that
lshd is started with the
right command-line options, possibly with supporting configuration files
generated as needed (see Defining Services).
Occasionally, instead of using the base services as is, you will want to
customize them. For instance, to change the configuration of
guix-daemon and Mingetty (the console log-in), you may write the
following instead of %base-services:
(modify-services %base-services (guix-service-type config => (guix-configuration (inherit config) (use-substitutes? #f) (extra-options '("--gc-keep-outputs")))) (mingetty-service-type config => (mingetty-configuration (inherit config) (motd (plain-file "motd" "Hi there!")))))
The effect here is to change the options passed to
when it is started, as well as the “message of the day” that appears
when logging in at the console. See
modify-services, for more on that.
The configuration for a typical “desktop” usage, with the X11 display server, a desktop environment, network management, power management, and more, would look like this:
;; This is an operating system configuration template ;; for a "desktop" setup with X11. (use-modules (gnu) (gnu system nss)) (use-service-modules desktop) (use-package-modules xfce ratpoison certs) (operating-system (host-name "antelope") (timezone "Europe/Paris") (locale "en_US.UTF-8") ;; Assuming /dev/sdX is the target hard disk, and "root" is ;; the label of the target root file system. (bootloader (grub-configuration (device "/dev/sdX"))) (file-systems (cons (file-system (device "root") (title 'label) (mount-point "/") (type "ext4")) %base-file-systems)) (users (cons (user-account (name "bob") (comment "Alice's brother") (group "users") (supplementary-groups '("wheel" "netdev" "audio" "video")) (home-directory "/home/bob")) %base-user-accounts)) ;; Add Xfce and Ratpoison; that allows us to choose ;; sessions using either of these at the log-in screen. (packages (cons* xfce ratpoison ;desktop environments nss-certs ;for HTTPS access %base-packages)) ;; Use the "desktop" services, which include the X11 ;; log-in service, networking with Wicd, and more. (services %desktop-services) ;; Allow resolution of '.local' host names with mDNS. (name-service-switch %mdns-host-lookup-nss))
See Desktop Services, for the exact list of services provided by
%desktop-services. See X.509 Certificates, for background
information about the
nss-certs package that is used here.
See operating-system Reference, for details about all the available
Assuming the above snippet is stored in the my-system-config.scm
guix system reconfigure my-system-config.scm command
instantiates that configuration, and makes it the default GRUB boot
entry (see Invoking guix system).
The normal way to change the system’s configuration is by updating this
file and re-running
guix system reconfigure. One should never
have to touch files in
/etc or to run commands that modify the
system state such as
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.
Speaking of roll-back, each time you run
reconfigure, a new generation of the system is created—without
modifying or deleting previous generations. Old system generations get
an entry in the GRUB boot menu, allowing you to boot them in case
something went wrong with the latest generation. Reassuring, no? The
guix system list-generations command lists the system
generations available on disk.
At the Scheme level, the bulk of an
is instantiated with the following monadic procedure (see The Store Monad):
Return a derivation that builds os, an
object (see Derivations).
The output of the derivation is a single directory that refers to all the packages, configuration files, and other supporting files needed to instantiate os.