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Windows Partition Backup

This is description of how to backup raw partitions in preparation for switching a new machine to Linux. The main reason would be to preserve a brand new Windows licence key and driver installation to ease installation/restoration for switchimg the computer back at a later date.

Another method would be preferable (or at least more steps need to be taken) to set up dual boot or preserving/migrating data from a Windows installation currently in use (in which case rsync to a backup drive would be a better solution).

Windows Partition Backup

Preparation

Save a copy of your Windows activation key first: this should be stored in the UEFI/ACPI firmware MSDM table, but it is better to record ssomewhere safely. You may also have a hard copy in the documetation that came with (or a sticker right on) your new hardware.

Start up the computer and press Shift+F10 to open up a command prompt in the Windows installer and run (it may take a little while for the dialog to come up):

• powershell "(Get-CimInstance SoftwareLicensingService).OA3xOriginalProductKey"
• slmgr /dli and confirm that is the key in use

Partition Backup

1. Boot into a Linux recovery/live CD (I use Debian live CD)
   • You may need to disable secure boot in your BIOS first
2. On a high-DPI display, the console text may be very small:
   • sudo setfont /usr/share/consolefonts/Lat15-TerminusBold32x16.psf.gz to use a larger font.
3. Connect your backup media:
   • lsblk -f: pick the backup partition (for this example, I’ll use /dev/sdb3 — change to yours)
   • sudo mkdir /mnt/backup
   • sudo mount /dev/sdb3 /mnt/backup/
   • sudo mkdir /mnt/backup/windows
   • cd /mnt/backup/windows/
   • sudo chmod go+w .
4. If you haven’t already recorded it, save your Windows activation key:
   • sudo strings /sys/firmware/acpi/tables/MSDM | tail -1 | tee activation.key
5. If you (like I did) are using the standard Debian Live image, you’ll need to install some software:
   • Connect to Wi-Fi if you haven’t connected up a wired connection:
     • wpa_passphrase <Your Wi-Fi SSID> | sudo tee /etc/wpa_supplicant.conf
     • sudo wpa_supplicant -B -i wlp0s20f3 -c /etc/wpa_supplicant.conf
     • sudo dhcpcd wlp0s20f3
   • sudo apt update
   • sudo apt install gdisk
   • sudo apt install partclone
6. Back up your Windows partition table (a couple of different ways):
   • fdisk -l and pick out your Windows drive (probably /dev/nvme0n1)
   • sudo sgdisk --backup=gpt.bin /dev/nvme0n1
   • sudo sfdisk --dump /dev/nvme0n1 > ptable.sfdisk
7. Back up the Windows partition contents:
   • lsblk -f to confirm that you have the standard Windows installation layout.
   • sudo partclone.vfat -c -s /dev/nvme0n1p1 | zstd > p1-efi.pcl.zst — EFI partition
   • sudo dd if=/dev/nvme0n1p2 | zstd > p2-msr.img.zst — Microsoft Reserved
   • sudo partclone.ntfs -c -s /dev/nvme0n1p3 | zstd > p3-windows.pcl.zst — Windows C: drive
   • sudo partclone.ntfs -c -s /dev/nvme0n1p4 | zstd > p4-recovery.pcl.zst — Windows Recovery
8. Disconnect the backup drive:
   • cd /
   • sudo umount /mnt/backup
9. You probably want to keep the existing EFI partition — check with:
   • sudo sgdisk -p /dev/nvme0n1 — it is probably the first one (1)
10. sudo sgdisk -d 2 -d 3 -d 4 /dev/nvme0n1 — delete the rest (other three: 2, 3, and 4)
11. While you are at it, you can create the new partitions (or just do it in the Debian installer):
    • sudo sgdisk -n 2:0:+512M -t 2:8300 -c 2:boot /dev/nvme0n1 — create a 500 MiB partition
    • sudo sgdisk -n 3:0:0 -t 3:8309 -c 3:root /dev/nvme0n1 — create a partition container for LUKS/LVM
    • Make sure there is no file system left to confuse the installer:
      • sudo wipefs -a /dev/nvme0n1p2 /dev/nvme0n1p3
12. Continue on with your Debian installation.