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Diffstat (limited to 'doc/guix.texi')
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diff --git a/doc/guix.texi b/doc/guix.texi index 8da9ad639c..9f08bc1a7e 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -2847,6 +2847,7 @@ instance to support new system services. * File Systems:: Configuring file system mounts. * User Accounts:: Specifying user accounts. * Services:: Specifying system services. +* Initial RAM Disk:: Linux-Libre bootstrapping. * Invoking guix system:: Instantiating a system configuration. * Defining Services:: Adding new service definitions. @end menu @@ -3259,6 +3260,76 @@ password. When @var{auto-login?} is true, log in automatically as @end deffn +@node Initial RAM Disk +@subsection Initial RAM Disk + +@cindex initial RAM disk (initrd) +@cindex initrd (initial RAM disk) +For bootstrapping purposes, the Linux-Libre kernel is passed an +@dfn{initial RAM disk}, or @dfn{initrd}. An initrd contains a temporary +root file system, as well as an initialization script. The latter is +responsible for mounting the real root file system, and for loading any +kernel modules that may be needed to achieve that. + +The @code{initrd} field of an @code{operating-system} declaration allows +you to specify which initrd you would like to use. The @code{(gnu +system linux-initrd)} module provides two ways to build an initrd: the +high-level @code{base-initrd} procedure, and the low-level +@code{expression->initrd} procedure. + +The @code{base-initrd} procedure is intended to cover most common uses. +For example, if you want to add a bunch of kernel modules to be loaded +at boot time, you can define the @code{initrd} field of the operating +system declaration like this: + +@example +(initrd (cut base-init <> + #:extra-modules '("my.ko" "modules.ko"))) +@end example + +It also handles common use cases that involves using the system as a +QEMU guest, or as a ``live'' system whose root file system is volatile. + +@deffn {Monadic Procedure} base-initrd @var{file-systems} @ + [#:qemu-networking? #f] [#:virtio? #f] [#:volatile-root? #f] @ + [#:extra-modules '()] +Return a monadic derivation that builds a generic initrd. @var{file-systems} is +a list of file-systems to be mounted by the initrd, possibly in addition to +the root file system specified on the kernel command line via @code{--root}. + +When @var{qemu-networking?} is true, set up networking with the standard QEMU +parameters. When @var{virtio?} is true, load additional modules so the initrd can +be used as a QEMU guest with para-virtualized I/O drivers. + +When @var{volatile-root?} is true, the root file system is writable but any changes +to it are lost. + +The initrd is automatically populated with all the kernel modules necessary +for @var{file-systems} and for the given options. However, additional kernel +modules can be listed in @var{extra-modules}. They will be added to the initrd, and +loaded at boot time in the order in which they appear. +@end deffn + +Needless to say, the initrds we produce and use embed a +statically-linked Guile, and the initialization program is a Guile +program. That gives a lot of flexibility. The +@code{expression->initrd} procedure builds such an initrd, given the +program to run in that initrd. + +@deffn {Monadic Procedure} expression->initrd @var{exp} @ + [#:guile %guile-static-stripped] [#:name "guile-initrd"] @ + [#:modules '()] [#:to-copy '()] [#:linux #f] @ + [#:linux-modules '()] +Return a derivation that builds a Linux initrd (a gzipped cpio archive) +containing @var{guile} and that evaluates @var{exp}, a G-expression, +upon booting. + +@var{linux-modules} is a list of @file{.ko} file names to be copied from +@var{linux} into the initrd. @var{to-copy} is a list of additional +derivations or packages to copy to the initrd. @var{modules} is a list +of Guile module names to be embedded in the initrd. +@end deffn + @node Invoking guix system @subsection Invoking @code{guix system} |