I am trying to answer a question in ASK concerning building a multiboot USB from scratch, but hit a wall with installing grub2 and the boot partition and grub folder.
Most of the answers I can find in Ask concerning installing grub refer to legacy grub not grub2.
I tried looking at the source code of mkusb but all I saw was a haze.
A link to the shellscript would be highly appreciated.
In mkusb I use the shellscript dus-persistent to create the persistent live system. It consists of several functions, and specifically the function grub_n_iso to create partitions and put things into them. (The name is inherited from an old system, where iso files were used.)
If you have already installed mkusb, you can read the file dus-persistent with less or with your favourite text editor.
less /usr/sbin/dus-persistent
If you have not installed it yet, you can read it via the following link,
phillw.net/isos/linux-tools/mkusb/dus-persistent
But I think you want more detailed information, that shows the details, where the third partition usbboot is created and filled with content (grub).
grub_n_isoecho "item 30"
echo "30
# make partitions: preparing $part" >> "$tailfile"
if $grubimg
then
/bin/echo -e "$inversvid using grub.img: keeping file system of $part: $resetvid "
else
echo "preparing $part ------------------------------------------------"
dd if=/dev/zero of="$part" bs=1024 count=1024 2>&1
sync
umount "$part" 2>&1
sync
sleep 1
mkfs.vfat -v -F 32 "$part"
echo " "
sync
sleep 0.5
fi
In several versions of Ubuntu when installed, it is difficult to create grub for the 'other' boot mode, particularly to create grub for BIOS mode when booted in UEFI mode. For this reason there is an image grub.img, prepared like described below, that can be used.
When suitable, the partition is created with mkfs.vfat, and it will be labeled usbboot.
label="usbboot"
dosfslabel "$part" "$label"
grub_n_isoecho "item 70"
echo "70
# installing bootloaders" >> "$tailfile"
if [ "$distr" == "opensuse" ]
then
grub_inst=grub2-install
else
grub_inst=grub-install
fi
if $grubimg
then
/bin/echo -ne "$inversvid UEFI Bootloader: $resetvid "
$grub_inst --force --removable --no-floppy --boot-directory="$targ1"/boot
--efi-directory="$targ1"/EFI/BOOT "$2" 2>&1
fi
if $biosbl
then
/bin/echo -ne "$inversvid UEFI Bootloader: $resetvid "
$grub_inst --force --removable --no-floppy --boot-directory="$targ1"/boot
--efi-directory="$targ1"/EFI/BOOT "$2" 2>&1
elif ! test -f "$looper"/boot/grub/grub.cfg
then
if test -f "$mkusb_sdir"/usb-pack_efi.tar.gz
then
if ! $upefi
then
echo "$inversvid Select 'upefi' to use 'usb-pack-efi' $resetvid"
fi
else
/bin/echo -e "$inversvid No 'grub.cfg' for the UEFI Bootloader found in the iso file $resetvid
${version% *} needs the package 'usb-pack-efi' with the file
'usb-pack_efi.tar.gz' to make a persistent live system with
this iso file boot in UEFI mode."
if test -f /usr/bin/apt-get
then
echo "You can use the following command lines in a terminal window.
sudo add-apt-repository ppa:mkusb/ppa
sudo apt-get update
sudo apt-get install usb-pack-efi"
else
echo "
Use search string 'ubuntu dus-plus' for the tarball 'dus-plus' which contains
'usb-pack-efi'. Be prepared to tweak the system manually afterwards. It may be
difficult to create a persistent live system in your linux distro."
echo "$separator"
fi
fi
if $grubimg
then
/bin/echo -e "$inversvid BIOS Bootloader via 'grub.img': $resetvid "
else
/bin/echo -ne "$inversvid BIOS Bootloader: $resetvid "
$grub_inst --force --removable --no-floppy --boot-directory="$targ1"/boot "$2" 2>&1
fi
fi
The command grub-install is used (in Ubuntu and Debian). It uses the option --efi-directory for the UEFI bootloader.
If the setting 'upefi' (usb-pack-efi) is selected or necessary, it will be extracted.
The command grub-install is used again. For obvious reasons it does not use the option --efi-directory for the BIOS bootloader.
grub_n_isoecho "item 80"
echo "80
# copying files ..." >> "$tailfile"
error=""
start copy/extract boot files (not upefi) ----------------------------
if ! $upefi && test -f "$looper"/boot/grub/grub.cfg
then
copy the boot files from the iso file
/bin/echo -e "$inversvid 64-bit bootloader: copy the boot files from the iso file $resetvid"
echo "looper=$looper"
echo "targ1=$targ1"
rsync -Ha --exclude=filesystem.squashfs "$looper/" "$targ1"
symlink_error_comment="rsync:$inversvid don't worry, $resetvid symlink errors are expected
because of the target file system."
/bin/echo -e "$symlink_error_comment"
#if [ "$disk_name_type" == "debian" ] && [ "$release" == "stretch" ]
#then
mount -o loop "$looper"/boot/grub/efi.img "$loopefi"
rsync -Ha "$loopefi/efi" "$targ1"
umount "$loopefi"
ls -l "$targ1"|grep ^d
find "$targ1/efi"
read -p "after rsync efi"
#fi
is_file "$targ1"/boot/grub/grub.cfg
if [ $? -ne 0 ]
then
echo "'$targ1/boot/grub/grub.cfg': file not found"
echo "This way to use ${version% } needs 'grub.cfg' from the source iso file,"
echo "and it is available in Debian and Ubuntu family *amd64 iso files"
clear_grn "$pid" "$looper" "$targ1" "$tailfile" "$usbdata"
exit
fi
tweak 1 grub.cfg
sed "$targ1"/boot/grub/grub.cfg
-e '/menuentry/a \ set root=(hd0,4)'
-e '/linux/s#/#($root)/#'
-e '/initrd/s#/#($root)/#'
> "$targ1"/boot/grub/grub.cfg0
sync
menu_entry_1 "$targ1"/boot/grub/grub.cfg0 "$targ1"/boot/grub/grub.cfg
if [ $? -ne 0 ]
then
error="$error - menu_entry_1: tweaking grub.cfg"
fi
rm "$targ1"/boot/grub/grub.cfg0
else # ... copy/extract boot files (upefi) ----------------------------
extract files originally from Andre's zip-file (except grub.cfg grub4dos/ ini/)
if $grubimg
then
/bin/echo -e "$inversvid Bootloaders via 'grub.img', skipping 'usb-pack_efi': $resetvid "
rm "$targ1"/boot/grub/grub.cfg
else
if test -f "$mkusb_sdir"/usb-pack_efi.tar.gz
then
echo "using usb-pack_efi.tar.gz"
tar -xvzf "$mkusb_sdir"/usb-pack_efi.tar.gz --directory "$targ1"
if [ $? -ne 0 ]
then
error="- tar: extracting usb-pack_efi"
fi
fi
fi
tweak 2 grub.cfg
if ! test -f "$targ1"/boot/grub/grub.cfg
then
< "$mkusb_sdir"/grub.cfg sed '2'q > "$targ1"/boot/grub/grub.cfg # copy two first lines
if [ $? -ne 0 ]
then
error="$error - sed: copying start of grub.cfg"
fi
fi
sync
sleep 0.5
cat "$targ1"/boot/grub/grub.cfg
append the rest of the file (after two first lines)
menu_name
< "$mkusb_sdir"/grub.cfg sed -e '1,2'd
-e '/menuentry "ubuntu/a \ set root=(hd0,4)'
-e '/menuentry "memtest/a \ set root=(hd0,3)'
-e '/loopback/d' -e 's#iso-scan/filename=/ubuntu.iso ##'
-e 's/loop/$root/'
-e "s%ubuntu.iso%$menuname%g"
-e "s/vmlinuz/$vmlinuz/"
-e "s/casper/$persist/g"
-e "s/initrd.lz/$initrd/"
-e '/menuentry/s/"./\U&/'
>> "$targ1"/boot/grub/grub.cfg
#read -p "at 'append the rest of the file (after two first lines)'
#disk_name_type=$disk_name_type"
if [ "$disk_name_type" == "debian" ]
|| [ "$disk_name_type" == "torios-debian" ]
|| [ "$disk_name_type" == "9w-debian-wheezy" ]
then
sed -i 's/persistent --/persistence --/' "$targ1"/boot/grub/grub.cfg
fi
if [ $? -ne 0 ]
then
error="$error - sed: appending grub.cfg"
fi
fi # end copy/extract boot files --------------------------------------
I do not add more detailed explanations now. Please specify exactly what needs to be explained, if you want more details.
grub.imgso that you can use such an image instead of running the whole mkusb and then overwrite most of what it has created. – sudodus Oct 27 '19 at 15:44