Subject: Re: [bug#41011] [PATCH] gnu: grub: Support for network boot via TFTP.

From: Efraim Flashner <[email-masked]>
Date: Mon, 14 Sep 2020 09:59:11 +0300

On Sun, Sep 13, 2020 at 07:46:01PM +0200, Stefan wrote:
> * gnu/bootloader/grub.scm (grub-efi-netboot-bootloader): New bootloader for
> network booting.
> (install-grub-efi-netboot): New bootloader installer for network booting.
> (grub-root-search): Set the root to "(tftp)" if the searched file is not stored
> on a local devices, i.e. an NFS share.
> ---
>  gnu/bootloader/grub.scm | 97 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 96 insertions(+), 1 deletion(-)
> 
> diff --git a/gnu/bootloader/grub.scm b/gnu/bootloader/grub.scm
> index e3febeefd0..552bc34f5a 100644
> --- a/gnu/bootloader/grub.scm
> +++ b/gnu/bootloader/grub.scm
> @@ -23,8 +23,10 @@
>  ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
>  
>  (define-module (gnu bootloader grub)
> +  #:use-module (guix build union)
>    #:use-module (guix records)
> -  #:use-module ((guix utils) #:select (%current-system))
> +  #:use-module (guix store)
> +  #:use-module ((guix utils) #:select (%current-system %current-target-system))
>    #:use-module (guix gexp)
>    #:use-module (gnu artwork)
>    #:use-module (gnu bootloader)
> @@ -46,8 +48,11 @@
>              grub-theme-color-highlight
>              grub-theme-gfxmode
>  
> +            install-grub-efi-netboot
> +
>              grub-bootloader
>              grub-efi-bootloader
> +            grub-efi-netboot-bootloader
>              grub-mkrescue-bootloader
>              grub-minimal-bootloader
>  
> @@ -295,6 +300,9 @@ code."
>          ((? file-system-label? label)
>           (format #f "search --label --set ~a"
>                   (file-system-label->string label)))
> +        ((? (lambda (device)
> +              (and (string? device) (string-contains device ":/"))) nfs-uri)
> +         "set root=(tftp)")
>          ((or #f (? string?))
>           #~(format #f "search --file --set ~a" #$file)))))
>  
> @@ -501,6 +509,87 @@ fi~%"))))
>                        "--bootloader-id=Guix"
>                        "--efi-directory" target-esp))))
>  
> +(define (install-grub-efi-netboot subdir)
> +  "Define a grub-efi-netboot bootloader installer for installation in SUBDIR,
> +which is usually efi/Guix or efi/boot."
> +  (let* ((system (string-split (or (%current-target-system)
> +                                   (%current-system))
> +                               #\-))
> +         (boot-efi-link (match system
> +                          (("i686" _ ...) "/bootia32.efi")
> +                          (("x86_64" _ ...) "/bootx64.efi")
> +                          (("arm" _ ...) "/bootarm.efi")
> +                          (("armhf" _ ...) "/bootarm.efi")
> +                          (("aarch64" _ ...) "/bootaa64.efi")
> +                          (("riscv" _ ...) "/bootriscv32.efi")
> +                          (("riscv64" _ ...) "/bootriscv64.efi")))

Don't forget the fall-through case, even if it's just
((_ ...) "/bootTODO.efi")

> +         (efi-bootloader (string-append (match system
> +                                          (("i686" _ ...) "i386-efi")
> +                                          (("x86_64" _ ...) "x86_64-efi")
> +                                          (("arm" _ ...) "arm-efi")
> +                                          (("armhf" _ ...) "arm-efi")
> +                                          (("aarch64" _ ...) "arm64-efi")
> +                                          (("riscv" _ ...) "riscv32-efi")
> +                                          (("riscv64" _ ...) "riscv64-efi"))
> +                                        "/core.efi")))

With the fall-through case here, can this be changed to
(("i686" _ ...) "i386-efi")
(("aarch64" _ ...) "arm64-efi")
(("riscv" _ ...) "riscv32-efi")
((_ ...) (string-append (first
                         (string-split
                           (nix-system->gnu-triplet
                             (or (%current-system)
                                 (%current-target-system)))
                           #\_))
                        "-efi"))

> +    (with-imported-modules
> +     '((guix build union))
> +     #~(lambda (bootloader target mount-point)
> +         "Install the BOOTLOADER, which must be the package grub, as e.g.
> +bootx64.efi or bootarm64.efi into SUBDIR, which is usually efi/Guix or efi/boot,
> +below the directory TARGET for the system whose root is mounted at MOUNT-POINT.
> +
> +MOUNT-POINT is the last argument in 'guix system init /etc/config.scm mnt/point'
> +or '/' for other 'guix system' commands.
> +
> +TARGET is the target argument given to the bootloader-configuration in
> +(operating-system
> + (bootloader (bootloader-configuration
> +              (target \"/boot\")
> +              …))
> + …)
> +TARGET is required to be an absolute path and must be provided by a TFTP server
> +as the TFTP root directory.
> +
> +GRUB will load tftp://server/SUBDIR/grub.cfg and this file will instruct it to
> +load more files from the store like tftp://server/gnu/store/…-linux…/Image.
> +
> +To make this possible two symlinks will be created. The first symlink points
> +relatively form TARGET/SUBDIR/grub.cfg to /boot/grub/grub.cfg. And the second
> +symlink points relatively from TARGET/%store-prefix to %store-prefix.
> +
> +It is important to note that these symlinks need to be relativ, as the absolute
> +paths on the TFTP server side are unknown.
> +
> +It is also important to note that both symlinks will point outside the TFTP root
> +directory and that the TARGET/%store-prefix symlink makes the whole store
> +accessible via TFTP. Possibly the TFTP server must be configured
> +to allow accesses outside its TFTP root directory. This may need to be
> +considered for security aspects."
> +         (use-modules ((guix build union) #:select (symlink-relative)))
> +         (let* ((net-dir (string-append mount-point target "/"))
> +                (sub-dir (string-append net-dir #$subdir "/"))
> +                (store-link (string-append net-dir (%store-prefix)))
> +                (grub-cfg "/boot/grub/grub.cfg")
> +                (grub-cfg-link (string-append sub-dir (basename grub-cfg)))
> +                (boot-efi-link (string-append sub-dir #$boot-efi-link)))
> +           ;; Prepare the symlink to the store.
> +           (mkdir-p (dirname store-link))
> +           (false-if-exception (delete-file store-link))
> +           (symlink-relative (%store-prefix) store-link)
> +           ;; Prepare the symlink to the grub.cfg, which points into the store.
> +           (false-if-exception (delete-file grub-cfg-link))
> +           (symlink-relative grub-cfg grub-cfg-link)
> +           ;; Install GRUB, which refers to the grub.cfg, with support for
> +           ;; encrypted partitions,
> +           (setenv "GRUB_ENABLE_CRYPTODISK" "y")
> +           (invoke/quiet (string-append bootloader "/bin/grub-mknetdir")
> +                         (string-append "--net-directory=" net-dir)
> +                         (string-append "--subdir=" #$subdir))
> +           ;; Prepare the bootloader symlink, which points to GRUB.
> +           (false-if-exception (delete-file boot-efi-link))
> +           (symlink #$efi-bootloader boot-efi-link))))))
> +
>  ^L
>  
>  ;;;
> @@ -533,6 +622,12 @@ fi~%"))))
>     (name 'grub-efi)
>     (package grub-efi)))
>  
> +(define grub-efi-netboot-bootloader
> +  (bootloader
> +   (inherit grub-efi-bootloader)
> +   (name 'grub-efi-netboot-bootloader)
> +   (installer (install-grub-efi-netboot "efi/Guix"))))
> +
>  (define grub-mkrescue-bootloader
>    (bootloader
>     (inherit grub-efi-bootloader)
> -- 
> 2.26.0
> 
> 
> 
> 

-- 
Efraim Flashner   <[email-masked]>   אפרים פלשנר
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