[PATCH] docs: Improve initrd documentation

[PATCH] docs: Improve initrd documentation

[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.

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.
+
+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
+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
 
 
@@ -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
 
 
-- 
2.34.1

Re: [PATCH] docs: Improve initrd documentation

[Daniel Kiper]

On Wed, Jun 28, 2023 at 05:12:04AM -0500, Glenn Washburn wrote:
> 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.
>
> 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>

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

Re: [PATCH] docs: Improve initrd documentation

[Oskari Pirhonen]

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On Wed, Jun 28, 2023 at 05:12:04 -0500, Glenn Washburn wrote:
> 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.
> 
> 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.
> +
> +A new-style initrd (for kernels greater than 2.6) containing one file

I'd personally say "newer than 2.6", but "greater than 2.6" is still
easy enough to understand.

> +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
> +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
>  
>  
> @@ -4090,9 +4123,10 @@ also @ref{GNU/Linux}.
>  Load, in order, all initial ramdisks for a Linux kernel image to be booted in

Your commit message mentions replacing references to "initial ramdisk"
with "initrd" which you did above. Did you mean to do that here too?

>  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.
>  

I would add "command" after the "@command{initrd}" bit.

This is cool stuff. I was not aware of this feature in GRUB.

- Oskari

> -This command is only available on x86 systems.
> +This command is only available on the pc platform for x86 systems.
>  @end deffn
>  
>  
> -- 
> 2.34.1
> 

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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

Re: [PATCH] docs: Improve initrd documentation

[Oskari Pirhonen]

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On Sat, Jul 29, 2023 at 07:28:40 +0200, Paul Menzel wrote:
> 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.
> 

The "on them" is fine IMO because it clarifies what part of the
documentation is being referred to. In info(1), the sentence gets
rendered as:

    For more information on initrds see the GNU/Linux kernel
    documentation ($URL) on them.

But, according to the texinfo docs, for HTML it gets rendered without
the inline URL.

It's just a matter of personal preference I guess. I have no strong
opinion in either direction.

> > +
> > +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
> 

Good catch.

> > +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>
> 

A v2 was posted July 3 [1], could you re-comment on there?

- Oskari

[1]: https://lists.gnu.org/archive/html/grub-devel/2023-07/msg00007.html

> 
> Kind regards,
> 
> Paul

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