Re: [PATCH] docs: Improve initrd documentation

[Paul Menzel]

Dear Glenn,


Thank you for all your work on GRUB.

Am 28.06.23 um 12:12 schrieb Glenn Washburn:
> Remove reference to "initial ramdisk" and replace with "initrd". This then
> covers the case of ramdisk and ramfs, which is the usual method with kernels
> 2.6 and greater. Add sentence with URL to initrd documentation Linux kernel.
> Also, add a section documenting how to have the initrd command generate a
> new-style initrd via a specially crafted argument and include an example.

(I’d format this as a list.)

> Update initrd16 to refer to the initrd section and make note that initrd16
> is only on the pc platform.
>
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
>   docs/grub.texi | 46 ++++++++++++++++++++++++++++++++++++++++------
>   1 file changed, 40 insertions(+), 6 deletions(-)
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index b39b72230c6f..bea86669191b 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -4076,10 +4076,43 @@ load a defective boot loader, such as SCO UnixWare 7.1.
>   @subsection initrd
>   
>   @deffn Command initrd file [file @dots{}]
> -Load, in order, all initial ramdisks for a Linux kernel image, and set
> -the appropriate parameters in the Linux setup area in memory.  This may only
> -be used after the @command{linux} command (@pxref{linux}) has been run.  See
> -also @ref{GNU/Linux}.
> +Load, in order, all initrds for a Linux kernel image, and set the
> +appropriate parameters in the Linux setup area in memory.  This may only
> +be used after the @command{linux} command (@pxref{linux}) has been run.
> +See @ref{GNU/Linux} for more info on booting GNU/Linux.  For more
> +information on initrds see the GNU/Linux kernel
> +@uref{https://docs.kernel.org/filesystems/ramfs-rootfs-initramfs.html,
> +documentation} on them.

The “on them” at the end sounds like a leftover. But I am no native speaker.

> +
> +A new-style initrd (for kernels greater than 2.6) containing one file
> +with leading path components can also be generated at run time. This
> +can be done by prefixing an argument with @code{newc:} followed by the
> +path of the file in the new initrd, a @code{:}, and then the GRUB file
> +path to the file data to be be included.
> +
> +For example:
> +@example
> +initrd newc:/etc/ssh/config:(hd0,2)/home/user/.ssh/config \
> +       newc:/etc/ssh/ssh_host_rsa_key:/etc/ssh/ssh_host_rsa_key \
> +       /boot/initrd.gz \
> +       newc:/init:/home/user/init.fixed
> +@end example
> +
> +This command will generate two new-style initrds on the fly. The first
> +contains the path @samp{/etc/ssh/config} with the contents of
> +@samp{(hd0,2)/home/user/.ssh/config} and the path
> +@samp{/etc/ssh/ssh_host_rsa_key} with the contents of
> +@samp{/etc/ssh/ssh_host_rsa_key} on the @var{root} device. Parent directory
> +paths will automatically be generated as needed. This first generated initrd
> +will then have @samp{/boot/initrd.gz} concatenated after it. Next, another
> +new-style archive will be generated with the contents of 
> @samp{/home/user/init.fixed}
> +in the path @samp{/init} and appended to the previous concatenation. Finally,
> +the result will be sent to the kernel when booted.
> +
> +Keep in mind that paths that comes later will take precendence. So in the

1.  come later
2.  precedence

> +example above, the generated path @samp{/init} will overwrite any @samp{/init}
> +in @samp{/boot/initrd.gz}. This can be useful when changing the main initrd
> +is undesirable or difficult.
>   @end deffn

(Today I learned something new. Nice feature.)

>   
>   
> @@ -4090,9 +4123,10 @@ also @ref{GNU/Linux}.
>   Load, in order, all initial ramdisks for a Linux kernel image to be booted in
>   16-bit mode, and set the appropriate parameters in the Linux setup area in
>   memory.  This may only be used after the @command{linux16} command
> -(@pxref{linux16}) has been run.  See also @ref{GNU/Linux}.
> +(@pxref{linux16}) has been run.  See also @ref{GNU/Linux} and the 
> @command{initrd}
> +(@pxref{initrd}) for more details.
>   
> -This command is only available on x86 systems.
> +This command is only available on the pc platform for x86 systems.
>   @end deffn

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul