Next: Connecting to Wireguard VPN, Previous: Customizing the Kernel, Up: System Configuration [Contents][Index]
Historically, Guix System is centered around an operating-system
structure. This structure contains various fields ranging from the
bootloader and kernel declaration to the services to install.
Depending on the target machine, that can go from a standard
x86_64
machine to a small ARM single board computer such as the
Pine64, the image constraints can vary a lot. The hardware
manufacturers will impose different image formats with various partition
sizes and offsets.
To create images suitable for all those machines, a new abstraction is
necessary: that’s the goal of the image
record. This record
contains all the required information to be transformed into a
standalone image, that can be directly booted on any target machine.
(define-record-type* <image> image make-image image? (name image-name ;symbol (default #f)) (format image-format) ;symbol (target image-target (default #f)) (size image-size ;size in bytes as integer (default 'guess)) (operating-system image-operating-system ;<operating-system> (default #f)) (partitions image-partitions ;list of <partition> (default '())) (compression? image-compression? ;boolean (default #t)) (volatile-root? image-volatile-root? ;boolean (default #t)) (substitutable? image-substitutable? ;boolean (default #t)))
This record contains the operating-system to instantiate. The
format
field defines the image type and can be efi-raw
,
qcow2
or iso9660
for instance. In the future, it could be
extended to docker
or other image types.
A new directory in the Guix sources is dedicated to images definition. For now there are four files:
Let’s have a look to pine64.scm. It contains the
pine64-barebones-os
variable which is a minimal definition of an
operating-system dedicated to the Pine A64 LTS board.
(define pine64-barebones-os (operating-system (host-name "vignemale") (timezone "Europe/Paris") (locale "en_US.utf8") (bootloader (bootloader-configuration (bootloader u-boot-pine64-lts-bootloader) (targets '("/dev/vda")))) (initrd-modules '()) (kernel linux-libre-arm64-generic) (file-systems (cons (file-system (device (file-system-label "my-root")) (mount-point "/") (type "ext4")) %base-file-systems)) (services (cons (service agetty-service-type (agetty-configuration (extra-options '("-L")) ; no carrier detect (baud-rate "115200") (term "vt100") (tty "ttyS0"))) %base-services))))
The kernel
and bootloader
fields are pointing to packages
dedicated to this board.
Right below, the pine64-image-type
variable is also defined.
(define pine64-image-type (image-type (name 'pine64-raw) (constructor (cut image-with-os arm64-disk-image <>))))
It’s using a record we haven’t talked about yet, the image-type
record,
defined this way:
(define-record-type* <image-type> image-type make-image-type image-type? (name image-type-name) ;symbol (constructor image-type-constructor)) ;<operating-system> -> <image>
The main purpose of this record is to associate a name to a procedure
transforming an operating-system
to an image. To understand why
it is necessary, let’s have a look to the command producing an image
from an operating-system
configuration file:
guix system image my-os.scm
This command expects an operating-system
configuration but how
should we indicate that we want an image targeting a Pine64 board? We
need to provide an extra information, the image-type
, by passing
the --image-type
or -t
flag, this way:
guix system image --image-type=pine64-raw my-os.scm
This image-type
parameter points to the pine64-image-type
defined above. Hence, the operating-system
declared in
my-os.scm
will be applied the (cut image-with-os
arm64-disk-image <>)
procedure to turn it into an image.
The resulting image looks like:
(image (format 'disk-image) (target "aarch64-linux-gnu") (operating-system my-os) (partitions (list (partition (inherit root-partition) (offset root-offset)))))
which is the aggregation of the operating-system
defined in
my-os.scm
to the arm64-disk-image
record.
But enough Scheme madness. What does this image API bring to the Guix user?
One can run:
mathieu@cervin:~$ guix system --list-image-types The available image types are: - pinebook-pro-raw - pine64-raw - novena-raw - hurd-raw - hurd-qcow2 - qcow2 - uncompressed-iso9660 - efi-raw - arm64-raw - arm32-raw - iso9660
and by writing an operating-system
file based on
pine64-barebones-os
, you can customize your image to your
preferences in a file (my-pine-os.scm) like this:
(use-modules (gnu services linux) (gnu system images pine64)) (let ((base-os pine64-barebones-os)) (operating-system (inherit base-os) (timezone "America/Indiana/Indianapolis") (services (cons (service earlyoom-service-type (earlyoom-configuration (prefer-regexp "icecat|chromium"))) (operating-system-user-services base-os)))))
run:
guix system image --image-type=pine64-raw my-pine-os.scm
or,
guix system image --image-type=hurd-raw my-hurd-os.scm
to get an image that can be written directly to a hard drive and booted from.
Without changing anything to my-hurd-os.scm
, calling:
guix system image --image-type=hurd-qcow2 my-hurd-os.scm
will instead produce a Hurd QEMU image.
Next: Connecting to Wireguard VPN, Previous: Customizing the Kernel, Up: System Configuration [Contents][Index]