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Julian Decker edited this page Nov 13, 2026 · 14 revisions

Installation

This guide is the short way through. The exact commands and every option are in the README.

There are two ways, both with the files of the latest release, so you do not have to build anything:

  • From a USB stick, with DHO800_DHO900_OOS_Install.GEL: the scope stays closed, OOS goes on the card that is inside, beside stock.
  • On a second card, with oos-<version>.img: you open the scope, your original card stays untouched in a drawer.

A scope that already runs OOS is updated with oos-<version>.oosupd: see Updates and Going Back.

From a USB stick

You need a FAT32 USB stick with at least 200 MiB free.

  1. Download DHO800_DHO900_OOS_Install.GEL and SHA256SUMS from the latest release. Compare the checksum: shasum -a 256 DHO800_DHO900_OOS_Install.GEL on macOS, sha256sum on Linux, certutil -hashfile DHO800_DHO900_OOS_Install.GEL SHA256 on Windows. It has to match the file's line in SHA256SUMS.
  2. Copy the file to the top folder of the stick and keep its name, the scope looks for it. Next to it, create an empty file oos-dry-run.txt: the first run then only checks and saves a rescue set.
  3. Start the stock system and put the stick into the front port. If Storage does not show the stick, switch off and on and look again.
  4. Storage > Upgrade, choose the file (about 16 MB; a small file starting with ._ comes from macOS, leave it) and start. It takes about a minute, and the screen says at the end whether it worked.
  5. Read oos-install.log on the stick on a computer. It ends with exit code 0.
  6. Delete oos-dry-run.txt and run the update again. The log now ends with OOS selected for the next power-on and exit code 0.
  7. Copy the folder OOS-rescue from the stick to a computer and keep it: it holds your calibration and the stock recovery.
  8. Switch off at the mains, wait 30 seconds and switch on. OOS starts. Go on with First Steps.

OOS starts once: the power-on after it starts stock again. To stay on OOS, set System > Boot mode to Persist.

This ran on a DHO924S whose stock system is a modified one; an unmodified stock system has not run it yet. The install goes ahead by itself on the models whose hardware OOS has run on: DHO804, DHO814, DHO824 (a DHO804 runs OOS) and DHO914S, DHO924S (from 0.1.6; up to 0.1.5 only the DHO924S). On any other model it stops, writes nothing, and oos-install.log says so: put an empty file oos-any-model.txt next to the .GEL file to go on anyway. A kernel that hangs before the first script would need the card taken out: read docs/install-usb.md first.

On a second card

You will open the scope, which voids the warranty. The boot SD card is inside. Your original card stays untouched in a drawer: OOS only ever goes on a second card.

What you need

  • A DHO800/DHO900. OOS has run on a DHO924S and on DHO804s (user reports).
  • A second SD card, best of the same size or larger, and a card reader. A smaller card works too, see step 2.
  • A computer: macOS with tools/sdcard-clone.sh, or Windows or Linux with the tools below.
  • This repository: git clone https://github.com/deckerjulian/oos.git

Steps

  1. Back up the original card. Take it out and make an image of the whole card: tools/sdcard-clone.sh on macOS, below for Windows and Linux. Verify it, keep the image in two places, then put the card away.

  2. Write the clone to the second card. From here on you only use this card. Cards of the same nominal size differ by a few MB; if write says the image is larger than the card, make a copy that fits and write that one. Only the stock /data partition at the end gets smaller, the original image is only read:

    tools/sdcard-clone.sh fit ~/oos-backup/sd-original.img diskM ~/oos-backup/sd-fit.img
tools/sdcard-clone.sh write ~/oos-backup/sd-fit.img diskM

    On Linux, give the card's size in bytes instead of diskM (lsblk -bdno SIZE /dev/sdX) and write with dd.

  3. Get the image. Either download oos-0.1.12.img from the release and check it against SHA256SUMS, or build it yourself: Building, on macOS or Linux, also on an x86-64 PC.

  4. Install OOS on the second card. Do the dry run first, it only prints the plan:

    diskutil unmountDisk /dev/diskM
sudo python3 boot/card-install.py install /dev/rdiskM --image oos-0.1.12.img --fallback-stock

    If the plan looks right, add --execute. The tool refuses cards without the stock layout.

  5. Select OOS for the next start:

    sudo python3 boot/switch.py oos /dev/rdiskM --execute
sudo python3 boot/switch.py show /dev/rdiskM

  6. Put the card into the scope, close it, connect Ethernet and switch on. Go on with First Steps.

The stock software has to stay on the card: OOS reads the scope's identity with its help.

Backing up and cloning the card

Any tool that copies a whole disk sector by sector works. Only tools/sdcard-clone.sh on macOS has been tested against a scope's card; the others are common tools that users named.

Watch out:

  • The whole card, never a partition. The card has no MBR and no GPT; its loader and the stock partition table sit outside anything a computer shows as a partition. A copy of partitions does not start.
  • Windows cannot read the card and offers to format it, Disk Management may offer to initialise it: always Cancel. Each of these writes onto the card.
  • Check the device twice before you write: an image written to the wrong disk destroys it.
  • Verify the backup, keep the image in two places, and keep the original card unchanged in a drawer. It holds your factory calibration and licences. From then on you only use the second card (same size or larger; for a smaller one see tools/sdcard-clone.sh fit in the README).

Windows

  • Win32 Disk Imager: the card's drive letter, a new file name ending in .img, Read Only Allocated Partitions unticked, Read. Then Verify Only with the same card and file: it must say "Verify Successful". For the clone: the second card's drive letter, the image, Write, then Verify Only. If the card gets no drive letter, use one of the next tools, which open the physical disk.
  • HDD Raw Copy Tool: source the card, target FILE (.img); for the clone, source the file, target the second card.
  • WinHex: a disk image of the physical medium (not of a partition); Tools > Disk Tools > Clone Disk for the clone.
  • USBImager: Read makes an image, Write with Verify ticked makes the clone.
  • Checksum of an image: certutil -hashfile sd-original.img SHA256.

macOS

tools/sdcard-clone.sh list                                       # the card, e.g. disk4
tools/sdcard-clone.sh read disk4 ~/oos-backup/sd-original.img     # reads, verifies, writes a .sha256
tools/sdcard-clone.sh write ~/oos-backup/sd-original.img disk5    # the second card: asks for the disk id, verifies

By hand: diskutil unmountDisk /dev/diskN, then sudo dd if=/dev/rdiskN of=sd-original.img bs=4m status=progress (rdiskN, the raw device, is much faster than diskN). Check: sudo shasum -a 256 /dev/rdiskN and shasum -a 256 sd-original.img must be equal.

Linux

lsblk -o NAME,SIZE,MODEL,TRAN                    # the card: /dev/sdX (or /dev/mmcblkN), not sdX1
sudo dd if=/dev/sdX of=sd-original.img bs=4M status=progress conv=fsync
sudo sha256sum /dev/sdX sd-original.img          # must be equal
sudo dd if=sd-original.img of=/dev/sdY bs=4M status=progress conv=fsync      # the clone, second card /dev/sdY
sudo cmp -n "$(stat -c %s sd-original.img)" sd-original.img /dev/sdY && echo same

tools/sdcard-clone.sh needs macOS, except fit (a copy of the image for a smaller card), which takes the card's size in bytes on Linux. More detail: docs/sdcard-backup.md.

Over ADB

The README also describes an install over ADB, which needs a modified stock system and a build of your own.

OOS

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