How can I customise an ISO image of Webconverger with a Linux shell script?

Question

I want to write a simple shell script that downloads the latest ISO image of Webconverger and changes the boot parameters of grub in /boot/live.cfg.

So this is what I have done so far:

#!/bin/bash
# 1. Download the ISO
wget https://build.webconverger.com/latest.iso

# 2. Mount the ISO and create a development folder
sudo mkdir /mnt/webconverger
sudo mount -o loop latest.iso /mnt/webconverger

mkdir devfolder
rsync -av /mnt/webconverger/ devfolder/

sudo umount /mnt/webconverger
sudo rm -r /mnt/webconverger

# 3. Change the file in the development folder. 
chmod -R 777 devfolder/

rm devfolder/boot/live.cfg
echo \
"DEFAULT de

label de
    menu label Start
    kernel /live/vmlinuz
    append initrd=/live/initrd.img boot=live skipconfig quiet splash components=gitfs net.ifnames=0 bootfrom=removable locale=de xkb=-layout%20de homepage=https://www.google.de/" \
> devfolder/boot/live.cfg

# 4. Create a new ISO image
mkisofs -o new.iso -l devfolder
rm -r devfolder/

The generated ISO does not boot. I asume the reasons for the problem are, ~~that I had to run the whole script with root privileges and~~ that I need a more complex mkisofs command.

Does anybody know how to generate a proper ISO image for Webconverger with a shell script? Or is there an alternative method for the whole process? Something like ISO Master but for the command line?

Update

I have replaced the code snippets with the actual shell script. So it is easier to test. And here is the command line output (without the wget part):

mount: /dev/loop0 is write-protected, mounting read-only
sending incremental file list
./
boot/
boot/boot.bin
boot/boot.cat
boot/live.cfg
boot/syslinux/
boot/syslinux/ldlinux.c32
boot/syslinux/libcom32.c32
boot/syslinux/libutil.c32
boot/syslinux/splash.png
boot/syslinux/syslinux.cfg
boot/syslinux/vesainfo.c32
boot/syslinux/vesamenu.c32
live/
live/initrd.img
live/vmlinuz
live/filesystem.git/
live/filesystem.git/HEAD
live/filesystem.git/config
live/filesystem.git/description
live/filesystem.git/packed-refs
live/filesystem.git/shallow
live/filesystem.git/branches/
live/filesystem.git/hooks/
live/filesystem.git/hooks/applypatch-msg.sample
live/filesystem.git/hooks/commit-msg.sample
live/filesystem.git/hooks/post-update.sample
live/filesystem.git/hooks/pre-applypatch.sample
live/filesystem.git/hooks/pre-commit.sample
live/filesystem.git/hooks/pre-push.sample
live/filesystem.git/hooks/pre-rebase.sample
live/filesystem.git/hooks/pre-receive.sample
live/filesystem.git/hooks/prepare-commit-msg.sample
live/filesystem.git/hooks/update.sample
live/filesystem.git/info/
live/filesystem.git/info/exclude
live/filesystem.git/objects/
live/filesystem.git/objects/info/
live/filesystem.git/objects/pack/
live/filesystem.git/objects/pack/pack-1aa978c13266848f4644754d1875dc90ec4bfcdb.idx
live/filesystem.git/objects/pack/pack-1aa978c13266848f4644754d1875dc90ec4bfcdb.pack
live/filesystem.git/refs/
live/filesystem.git/refs/heads/
live/filesystem.git/refs/heads/master
live/filesystem.git/refs/remotes/
live/filesystem.git/refs/remotes/origin/
live/filesystem.git/refs/remotes/origin/HEAD
live/filesystem.git/refs/tags/
live/filesystem.git/refs/tags/initial-revision

sent 598,528,659 bytes  received 726 bytes  239,411,754.00 bytes/sec
total size is 598,380,033  speedup is 1.00
I: -input-charset not specified, using utf-8 (detected in locale settings)
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Total translation table size: 0
Total rockridge attributes bytes: 0
Total directory bytes: 30720
Path table size(bytes): 222
Max brk space used 2b000
292387 extents written (571 MB)

And this what I get in VirtualBox: Click here!

score 2 · Answer 1 · edited Jun 20 '20 at 09:12

So the full answer to the question is:

#!/bin/bash
# 1. Download the ISO
wget https://build.webconverger.com/latest.iso

# 2. Mount the ISO and create a development folder
sudo mkdir /mnt/webconverger
sudo mount -o loop latest.iso /mnt/webconverger

mkdir devfolder
rsync -av /mnt/webconverger/ devfolder/

sudo umount /mnt/webconverger
sudo rm -r /mnt/webconverger

# 3. Change the file in the development folder. 
echo \
"DEFAULT de

label de
    menu label Start
    kernel /live/vmlinuz
    append initrd=/live/initrd.img boot=live skipconfig quiet splash components=gitfs net.ifnames=0 bootfrom=removable locale=de xkb=-layout%20de homepage=https://duckduckgo.com nobrand" \
| sudo tee devfolder/boot/live.cfg

# 4. Create a new ISO image
sudo mkisofs -r -J -l -V "Webconverger" -b boot/boot.bin -c boot/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o new.iso devfolder
sudo isohybrid new.iso
sudo rm -r devfolder/

For some reason dd did not work for Webconverger images. Even the with the untouched latest.iso it was not possible to create a bootable USB flash drive. So I used Win32DiskImager.

score 1 · Accepted Answer · answered Jul 10 '18 at 22:20

What you want to do is to generate an El Torito bootable CD with an MBR in its first bytes.

mkisofs(8) needs some special options to create an "El Torito" bootable CD:

mkisofs -r -J -l -V "Webconverger" -b boot/boot.bin -c boot/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -o new.iso devfolder

Explaination:

-r -J: Enable Joliet and Rock Ridge meta data.
-l: Allow long filenames.
-V: Set volume ID. Optional.
-b: Specify the "El Torito" boot image.
-c: Specify the "El Torito" boot catalog.
-no-emul-boot: Specify that this is an "El Torito" bootable CD.
-boot-load-size: number of 512 bytes sector to load (4 is what usually works)
-boot-info-table: modify the original boot image appending the Boot Info Table

Then, if you want to be able to just dd the file on a USB drive you will need to write an MBR onto the ISO:

isohybrid new.iso

Thank you! This works like a charm. I still get `I: -input-charset not specified, using utf-8 (detected in locale settings)` and I do not exactly know what it means. — ukqz, Jul 11 '18 at 09:42
It means that it is interpreting input file names as they were UTF-8 encoded. This is probably a safe choice, unless you have reasons to believe that the file names are in another encoding. — smeso, Jul 11 '18 at 09:48

How can I customise an ISO image of Webconverger with a Linux shell script?

Update

2 Answers2

So the full answer to the question is: