Bootiso should allow creation of GPT partitions in mount-rsync mode

[jsamr]

Keeping track suggestion from @Sporif in #15.
Not scheduled anytime soon; feel free to upvote if you'd like this feature to be implemented.

[dilbert-tctc]

yes please, it is a like to have feature but not a must have feature right now. thanks.

[mevdschee]

When you want to write the latest Windows 10 (Win10_1809Oct_EnglishInternational_x64.iso) to an USB drive to boot in EUFI mode it requires a GPT partition table and contains the ISO contains a 4.1 GB file (install.wim) so it also requires an NTFS partition. Rufus uses UEFI:NTFS and creates a 512kB FAT16 partition with EFI folder to boot from (with disabled secure boot). The partition table looks like this:

You can probably imagine that this is difficult to do manually and that it could be a popular feature.

[jsamr]

@mevdschee Have you tried with the wimsplit feature shipped in 3.2 version ?

[mevdschee]

Wow.. I just learned about wimsplit.. I'm going to try it out and let you know. Thank you very much!

[mevdschee]

I succeeded to run the latest version, but it failed when splitting. Could it be that the ISO is loop-mounted in read-only mode and that wim-split fails due to that? When I split manually everything works fine!

[jsamr]

@mevdschee perhaps you don't have wimsplit 1.13 and you fall under #43 bug!

[mevdschee]

@jsamr Thank you, you are right. That is the problem. I'm having wimtools 1.12.

[mevdschee]

Just sharing my achievement/findings.

Instead of splitting the "install.wim" into parts (this is not supported in the Win10 installer) I recompressed the "install.wim" and went from 4.4Gb to 3.3Gb. The command I used was:

$ time wimlib-imagex optimize install.wim --solid
"install.wim" original size: 4253057 KiB
Using LZMS compression with 4 threads
Archiving file data: 9344 MiB of 9344 MiB (100%) done
"install.wim" optimized size: 3175915 KiB
Space saved: 1077141 KiB

real	36m26,364s
user	127m4,804s
sys	0m10,063s

After this I was able to do a signed UEFI Win10 Oct 2018 (Win10_1809) install from FAT32 (GPT partition table) on my Acer Swift 1.

I prefer this approach over the Rufus approach of using an unsigned NTFS driver in an FAT32 EFI partition.

I explained the approach in more detail here: https://tqdev.com/2019-cannot-copy-windows-10-install-wim

NB: I learned that you can actually have multiple partitions (FAT32 + NTFS) and split your ISO content over them (this is supported by the windows installer), see: https://www.tenforums.com/tutorials/118137-create-bootable-usb-installer-if-install-wim-greater-than-4gb.html

[jsamr]

GPT support is getting cooked for 4.0 release, get ready!