Re: grub-mkimage

[Pascal]

hi,

thank you Andrei for taking the time to read and answer me.

I try to reduce the space taken by GRUB as much as possible.
this way, I only have the bootloader and a basic configuration file :

# ll -h /run/live/bootmnt/efi/boot/bootx64.efi
-rwxr-xr-x 1 root root 584K 26 janv. 07:46
/run/live/bootmnt/efi/boot/bootx64.efi

# cat /run/live/bootmnt/efi/menu.cfg
menuentry MyLiveSystem {
linux /boot/kernel ...
initrd /boot/initramfs
}

I tried to remove efi_gop and efi_uga but I always get (at least with Qemu)
the following error message :

error: no suitable video mode found.
Booting in blind mode

adding video and/or video_fb modules (which are required/used by efi_*
modules) does not change anything.

I tried to use grub-mkstandalone but I fail to generate a bootloader that
works as simply as my tiny one.
here is the command used :

grub-mkstandalone \
   --disable-shim-lock \
   --fonts="" --locales="" --themes="" \
   --modules="linux normal minicmd gzio efi_uga efi_gop fat part_gpt chain"
\
   -o /run/live/bootmnt/efi/boot/test.efi \
   -O x86_64-efi \
   "boot/grub/grub.cfg=/run/live/bootmnt/efi/menu.cfg"

as root and prefix use (memdisk), I get the following error message :

error: file `/boot/kernel' not found.

only the cmdpath variable refers to my disk with (hd0,gpt2)/efi/boot.
it works once the root variable is manually set to (hd0,gpt2) (but not with
(,gpt2)).

as you are involved in the development of GRUB, I have a small remark about
grub-mkstandalone : the SOURCE parameter is not discussed in its man page
apart from the general presentation (eg. invocation).
I found my last parameter ("boot/grub/grub.cfg=...") on the internet : what
more information/option can be passed ? prefix may be ?

a last question (for today ;-)) to which I did not find an answer : is it
possible to switch the bootloader to verbose mode ?

regards, lacsaP.

Le mar. 25 janv. 2022 à 18:25, Andrei Borzenkov <arvidjaar@gmail.com> a
écrit :

> On 25.01.2022 17:23, Pascal wrote:
> > when I use grub-mkimage, the generated EFI executable automatically loads
> > the embedded modules which explains this change in behavior.
> > and so I don't need this command insmod linux normal minicmd gzio efi_uga
> > efi_gop fat part_gpt in my configuration file.
> > On the contrary, grub-mkstandalone incorporates all the modules in the
> EFI
> > executable that will be generated (unless the use of the
> --install-modules
> > option) but the latter will only preload those listed in the --modules
> > option.
> > is this right ?
> >
>
> Yes.
>
> > except chain, do you know if these nine modules are the "vital minimum"
> to
> > boot my roaming live system present on the second partition of a USB key
> -
> > or even an internal disk - partitioned in GPT in a UEFI environment ?
> > if (,gpt2) means "the second partition on the disk grub was loaded from",
> > then I'm sure to boot the system selected from the UEFI firmware and not
> > another system that might be present on another drive ?
> >
>
> You do not really need efi_uga or efi_gop unless you want to display pretty
> pictures.
>
> But EFI does not have memory constraints of legacy BIOS, so what not simply
> have all modules?
>
> > Le mar. 25 janv. 2022 à 13:06, Andrei Borzenkov <arvidjaar@gmail.com> a
> > écrit :
> >
> >> On Tue, Jan 25, 2022 at 12:13 PM Pascal <patatetom@gmail.com> wrote:
> >>>
> >>> hi,
> >>>
> >>> first of all, a small precision which can be important : I use version
> >> 2.06 of GRUB.
> >>>
> >>> in both cases (tiny and full EFI), /efi/boot/bootx64.efi and /boot/ are
> >> on the same partition (gpt2).
> >>>
> >>> in first case, these few modules allow me to access my configuration
> >> file (/efi/boot/bootx64.efi read /efi/menu.cfg) and to boot my kernel
> >> (linux /boot/kernel) with its initialization file (initrd
> /boot/initramfs).
> >>>
> >>> in the second case, the presence of all modules disturbs the expected
> >> behavior. I don't think that grub-mkstandalone will add more modules
> than
> >> the ones requested in this case.
> >>>
> >>
> >> I never said "it will add more modules". I said "it will add modules
> >> differently so they will not interfere with grub loading".
> >>
> >>> I added the nativedisk module (which has no dependency according to
> >> /usr/lib/grub/x86_64-efi/moddep.lst) to the few modules of the first
> case
> >> and it didn't change anything to its behavior : GRUB accesses its
> >> configuration file and boots my roaming live system.
> >>> this module doesn't seem to be the one that modifies GRUB's behaviour
> >> towards (,gpt2)/efi/boot prefix.
> >>>
> >>> in first case (with or without nativedisk), the ls command played in
> the
> >> GRUB console (hd0) (hd0,gpt2) (hd0,gpt1) (hd1) (cd0) (where (hd0) is my
> >> live disk).
> >>
> >> It is not enough to have the "nativedisk" module, you also need to
> >> have low level drivers (ahci, etc depending on your hardware). I
> >> assume nativedisk simply did not detect any native driver and its
> >> loading became noop.
> >>
> >>> in second case, it returns (ahci1) (ahci1,msdos1) (ahci0) (ahci0,gpt2)
> >> (ahci0,gpt1) (ahci2) (where (ahci0) is my live disk).
> >>>
> >>
> >> Well, (,gpt2) means "the second partition on the disk grub was loaded
> >> from". I doubt that grub magic to detect this disk will work with
> >> native drivers on UEFI (actually I am pretty sure it won't).
> >>
> >> nativedisk drivers were never intended for BIOS/UEFI systems.
> >>
> >>> regards, lacsaP.
> >>>
> >>> Le lun. 24 janv. 2022 à 19:28, Andrei Borzenkov <arvidjaar@gmail.com>
> a
> >> écrit :
> >>>>
> >>>> On 24.01.2022 17:53, Pascal wrote:
> >>>>> hi,
> >>>>> I use grub successfully to boot my removable "UEFI only" roaming live
> >>>>> system.
> >>>>> I use grub-mkimage as follows to generate the EFI executable :
> >>>>>
> >>>>> cat > /tmp/cfg <<< "normal /efi/menu.cfg"
> >>>>>
> >>>>> grub-mkimage  \
> >>>>>   --disable-shim-lock  \
> >>>>>   -p "(,gpt2)/efi/boot/"  \
> >>>>>   -o /run/live/bootmnt/efi/boot/bootx64.efi  \
> >>>>>   -O x86_64-efi  \
> >>>>>   -c /tmp/cfg  \
> >>>>>   linux normal minicmd gzio efi_uga efi_gop fat part_gpt chain
> >>>>>
> >>>>> cat > /run/live/bootmnt/efi/menu.cfg <<~~~~
> >>>>> insmod linux normal minicmd gzio efi_uga efi_gop fat part_gpt
> >>>>> menuentry "My Live Linux" {
> >>>>>       linux …
> >>>>>       initrd …
> >>>>> }
> >>>>> ~~~~
> >>>>>
> >>>>> the executable being really minimal, I can't do much with it when I
> >>>>> encounter a boot problem.
> >>>>> so, I set up another EFI executable next to it, this time with all
> the
> >>>>> available modules :
> >>>>>
> >>>>> mods=$( ls -1 /usr/lib/grub/x86_64-efi/*.mod | sed -e
> >>>>> 's;/usr/lib/grub/x86_64-efi/;;g' -e 's/\.mod$//g' | tr '\n' ' ' )
> >>>>>
> >>>>> echo $mods
> >>>>> acpi adler32 affs afs afsplitter ahci all_video aout appleldr archelp
> >>>>> at_keyboard ata backtrace bfs bitmap bitmap_scale blocklist boot
> >> boottime
> >>>>> bsd bswap_test btrfs bufio cacheinfo cat cbfs cbls cbmemc cbtable
> >> cbtime
> >>>>> chain cmdline_cat_test cmp cmp_test configfile cpio cpio_be cpuid
> >> crc64
> >>>>> crypto cryptodisk cs5536 ctz_test date datehook datetime disk
> >> diskfilter
> >>>>> div div_test dm_nv echo efi_gop efi_uga efifwsetup efinet ehci elf
> >> eval
> >>>>> exfat exfctest ext2 extcmd f2fs fat file fixvideo font fshelp
> >>>>> functional_test gcry_arcfour gcry_blowfish gcry_camellia gcry_cast5
> >>>>> gcry_crc gcry_des gcry_dsa gcry_idea gcry_md4 gcry_md5 gcry_rfc2268
> >>>>> gcry_rijndael gcry_rmd160 gcry_rsa gcry_seed gcry_serpent gcry_sha1
> >>>>> gcry_sha256 gcry_sha512 gcry_tiger gcry_twofish gcry_whirlpool geli
> >> gettext
> >>>>> gfxmenu gfxterm gfxterm_background gfxterm_menu gptsync gzio halt
> >> hashsum
> >>>>> hdparm hello help hexdump hfs hfsplus hfspluscomp http iorw iso9660
> >> jfs
> >>>>> jpeg json keylayouts keystatus ldm legacy_password_test legacycfg
> >> linux
> >>>>> linux16 loadbios loadenv loopback ls lsacpi lsefi lsefimmap
> >> lsefisystab
> >>>>> lsmmap lspci lssal luks luks2 lvm lzopio macbless macho mdraid09
> >>>>> mdraid09_be mdraid1x memdisk memrw minicmd minix minix2 minix2_be
> >> minix3
> >>>>> minix3_be minix_be mmap morse mpi msdospart mul_test multiboot
> >> multiboot2
> >>>>> nativedisk net newc nilfs2 normal ntfs ntfscomp odc offsetio ohci
> >>>>> part_acorn part_amiga part_apple part_bsd part_dfly part_dvh part_gpt
> >>>>> part_msdos part_plan part_sun part_sunpc parttool password
> >> password_pbkdf2
> >>>>> pata pbkdf2 pbkdf2_test pcidump pgp play png priority_queue probe
> >> procfs
> >>>>> progress raid5rec raid6rec random rdmsr read reboot regexp reiserfs
> >>>>> relocator romfs scsi search search_fs_file search_fs_uuid
> search_label
> >>>>> serial setjmp setjmp_test setpci sfs shift_test signature_test sleep
> >>>>> sleep_test smbios spkmodem squash4 strtoull_test syslinuxcfg tar
> >> terminal
> >>>>> terminfo test test_blockarg testload testspeed tftp tga time tpm tr
> >> trig
> >>>>> true udf ufs1 ufs1_be ufs2 uhci usb usb_keyboard usbms
> >> usbserial_common
> >>>>> usbserial_ftdi usbserial_pl2303 usbserial_usbdebug usbtest video
> >>>>> video_bochs video_cirrus video_colors video_fb videoinfo videotest
> >>>>> videotest_checksum wrmsr xfs xnu xnu_uuid xnu_uuid_test xzio zfs
> >> zfscrypt
> >>>>> zfsinfo zstd
> >>>>>
> >>>>> grub-mkimage  \
> >>>>>   --disable-shim-lock  \
> >>>>>   -p "(,gpt2)/efi/boot"  \
> >>>>>   -o /run/live/bootmnt/efi/boot/helpx64.efi  \
> >>>>>   -O x86_64-efi  \
> >>>>>   -c /tmp/cfg  \
> >>>>>   $mods
> >>>>>
> >>>>> however, when I choose to boot this one, I get the following error :
> >>>>>
> >>>>> error: disk `,gpt2' not found.
> >>>>> error: you need to load the kernel first.
> >>>>>
> >>>>> does anyone know why the *minimal* is fully functional while the
> >> *maximal*
> >>>>> refuses to consider (,gpt2)/efi/boot/ ?
> >>>>>
> >>>>
> >>>> Modules listed in grub-mkimage are intended only for access to
> >> /boot/grub
> >>>> directory and are initialized when grub image is executed. One of
> >> modules
> >>>> is nativedisk which replaces firmware disk drivers with native drivers
> >> (like
> >>>> ahci. usb, etc). These driver are using different name conventions so
> >> none of
> >>>> them recognizes gpt2. Moreover, I am not really sure whether those
> >> drivers
> >>>> will work under UEFI at all (they compete with UEFI for hardware
> >> access).
> >>>>
> >>>> If you need image with more grub modules consider using
> >> grub-mkstandalone. It
> >>>> creates image with embedded RAM disk and sets $prefix to refer to this
> >> disk.
> >>>> So you have usual grub environment with modules autoloading and avoid
> >> this
> >>>> problem. You can chose which modules are included into RAM disk. You
> >> can also
> >>>> create usual grub.cfg on this RAM disk which boots whatever you like
> >> automatically.
> >>>>
> >>
> >>
> >
>
>
>