Boot Loaders and BIOS control
Contents
Boot Loaders and BIOS control¶
Loose collection of notes and predominantly case studies for solutions to problems that develop before the operating system starts.
Table of Contents¶
Creating a Windows bootable USB drive¶
The Windows ISOs can be downloaded from the Microsoft homepage, and are language specific. The ISOs are just under 6 GB, with seemingly no net-install or lighter ISO available.
Using dd¶
Unmount the drive you wish to make bootable, e.g. a USB stick under /dev/sdd
sudo umount /dev/sdd
and format the drive as either FAT or NTFS. On linux distros, this can be done with the mkfs tool
sudo mkfs.vfat -I /dev/sdd
where the -I flag is to mitigate some errors with fixed disk devices.
Now we can copy our ISO onto the device
sudo dd if=path/to/windows.iso of=/dev/sdd bs=1M conv=sync status=progress
we throw in conv=sync for padding to ibs-size, and on newer versions of GNU dd (gdd) the status=progress will print how much data has been written to the device.
A few things to note:
as is stated in the UEFI Wikipedia article
The UEFI specification explicitly requires support for FAT32 for system partitions, and FAT12/FAT16 for removable media; specific implementations may support other file systems.
It is up to the manufacturer of the motherboard to include specific NTFS boot support. So far, in my own cases, I have been pretty lucky, however if you are unable to boot, this may be why.
FAT32 formatting supports a maximum individual file size of 4GB, thus Win10 ISOs may not fit in FAT32.
If your UEFI is preventing NTFS boot, you may require a crossover tool for UEFI-NTFS.
tools such as Rufus allow for UEFI boots from NTFS, however this is something I am personally yet to try.
Graphically¶
There are tools such as gparted, or woeusb which can automate some of this process.
But there is a tried and tested method which works using default GNOME linux tools. Open Disks, and select the drive you want to make bootable.
Unmount and format the partition for Windows (commonly NTFS), and remount the drive.
Open Nautilus (File Explorer), right click on your ISO and select Open With Disk Image Mounter, which will create a mounted volume on your file system with the contents of the ISO. From here, copy in the conventional sense (either drag and drop or using cp, etc.) the files from the ISO mount to the device mount.
This may be able to mitigate FAT32 restrictions, but I am unsure as I have not personally tested this.
Booting/Installing with UEFI¶
Provided you are able to boot from an ISO loaded on your device, the next step is to install the operating system.
There are now some issues that may arrise relating to the destination drive’s partition table.
The format of prexisting partitions doesn’t matter, as most installers will provide reformatting and partitioning tools. However, the drive’s partition scheme label does make a difference.
If you are using BIOS Legacy Mode, Master Boot Record (MBR) and GUID Partition Table (GPT) partitions schemes are supported, however UEFI can only install on GPT.
The easiest way to check and change your partition label is with fdisk and parted (sudo apt-get install parted). We can view our drives with
sudo fdisk -l
and will see something like
Disk /dev/sdb: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Disk model: ST3500418AS
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 0495045D-8196-419B-B4F5-5EDF681E3D27
Here, we see in the second to last line the Disklabel type is GPT. If this were something else, e.g. MS-DOS, we would need to use parted to update the label.
NB: changing the label is a very easy way to “lose” all your data on the disk. Backup first.
sudo parted /dev/sdb mklabel gpt
Changing the label will also clear the partition table.
Updating GRUB¶
In the GRUB documentation are listed a few ways to edit the GRUB settings manually, including by editing the grub.d configuration files.
Another method, slightly more automated, is to mount the partitions containing the alternative OS on your linux host, somewhere on /, and then use
sudo os-prober
to see if the OS is detected.
Then use
sudo update-grub
in order to add the detected OSs into the GRUB menu.
Note that the EFI boot may not be on the same partition as the OS itself, which I, at first, found a little perplexing.