ArashOS

Install

Install ArashOS

Write the installer to a USB stick, start the computer from it, and answer a few questions. Nothing on the computer's disks changes until the last question.

Before you start

Back up your files. Then read what doesn't work yet:

  • The USB stick starts only with Secure Boot turned off in the computer’s startup (BIOS or UEFI) settings. Once ArashOS is installed, the welcome can turn it on with your own keys.
  • The installer can’t yet split a disk the way you choose: ArashOS takes the whole disk, the free space or the partition you choose.
  • The installer on this USB stick has been tried in virtual machines only. ArashOS runs every day on three computers: an Intel laptop, an NVIDIA laptop and a desktop with two NVIDIA cards and three screens. On other hardware it may not work. Back up your files first, and tell us what happens: hello@arashos.org.

Write the USB stick

You need a USB stick of 2 GB or larger and the installer, arashos-2026.11.1-x86_64.iso, checked. Writing it erases everything on the stick. Copying the file onto the stick isn't enough: it has to be written as a whole, in one of these ways.

On Linux

Plug in the stick and list the USB drives:

ls /dev/disk/by-id/usb-*

The stick is the name without -part at the end, such as usb-SanDisk_Ultra_1234-0:0. Only USB drives are listed there, so the computer's own disk can't be picked by mistake. Write the installer to it, with your stick's name in place of the example:

sudo dd if=arashos-2026.11.1-x86_64.iso \
  of=/dev/disk/by-id/usb-SanDisk_Ultra_1234-0:0 \
  bs=4M conv=fsync oflag=direct status=progress

It's done when the command returns.

On Windows

Use Rufus, a free program that writes USB sticks.

  1. Plug in the stick and open Rufus.
  2. Under Device, choose the stick.
  3. Press Select and choose arashos-2026.11.1-x86_64.iso.
  4. Press Start. When Rufus asks how to write the image, choose Write in DD Image mode, then OK.

On a Mac

To make the stick for another computer. ArashOS itself hasn't been tried on a Mac. In Terminal, find the stick's number by its size:

diskutil list

If the stick is /dev/disk4, write the installer to it with:

diskutil unmountDisk /dev/disk4
sudo dd if=arashos-2026.11.1-x86_64.iso of=/dev/rdisk4 bs=1m

When it's done, macOS may say it can't read the disk. Choose Ignore, or Eject.

Start from the stick

  1. Turn Secure Boot off

    Secure Boot lets a computer start only software signed with keys it trusts. The stick isn't signed with a key your computer has yet, so turn Secure Boot off in the computer's startup settings (called BIOS or UEFI settings). To open them, press a key just as the computer starts, often F2, Del or Esc; the computer's maker says which. Secure Boot is usually under Security or Boot. Save and leave.

    If Windows is on the computer and uses BitLocker (Windows's own disk encryption), find its recovery key first. Windows may ask for it once after Secure Boot changes.

  2. Choose the stick in the startup menu

    Plug in the stick and start the computer. Press the startup menu key as it starts, often F12, F11, F9 or Esc, and choose the stick. It may be named by its maker, with UEFI in front.

  3. Choose ArashOS install medium

    The stick shows its own menu. Choose ArashOS install medium. The installer opens by itself.

If the stick doesn't start, Secure Boot is probably still on, or the computer is set to start the old way (BIOS, sometimes called Legacy or CSM). ArashOS needs UEFI.

What the installer asks

The installer is text on a dark screen. Use the arrow keys and Enter; every screen shows the keys it takes at the bottom.

Keyboard
The keyboard you type on. The installer uses it from then on, and so does ArashOS.
Internet
A cable, or a Wi-Fi network from the list. The installer downloads part of ArashOS while it installs, so it needs to stay connected. ArashOS joins the same Wi-Fi by itself afterwards.
Where it goes
A whole disk, a free space on a disk, or a partition (a part of a disk) that ArashOS replaces. Windows and other systems elsewhere stay, and you can start them from the menu when the computer starts. If your choice erases something, the next screen says what. ArashOS runs every day on a computer with Windows 11 on a disk of its own; the installer has put it beside Windows only in virtual machines so far, with a stand-in for Windows.
Disk encryption
ArashOS encrypts the whole disk: what's on it is scrambled, and only your passphrase turns it back into your files. You type it each time the computer starts, on an English (US) keyboard layout, so use only letters, numbers and signs a US keyboard has. Without it nobody can read the disk, not even you, so write it down somewhere safe.
Your account
Your name to sign in with, and a password. The password also lets you change system settings. Then a name for the computer on your network.
Language
For translated apps, and for how dates, numbers and money are written. ArashOS's own screens are in English for now.
Timezone
Where you are, for the clock.
Your computer
What the installer found (the processor, graphics, a fingerprint reader) and the drivers it adds. Nothing to choose.
Secure Boot
auto sets it up now when the computer is ready for new keys, which most aren't yet; off leaves it for later. Either way you can set it up after the first start.
Ready to install
Everything you chose, and what will be erased. To go ahead, type what the screen asks: ERASE and the name of what's erased (such as ERASE nvme0n1), or INSTALL for a free space. This is the first time anything on the disks changes.

Then it installs, with each step on the screen. When it says ArashOS is installed, take out the stick and press Enter to restart. If the install fails, the screen says why, and r tries again. Write to hello@arashos.org with what it says.

After the first start

  1. Type your passphrase

    The computer asks for the disk's passphrase before anything else starts. With Windows on the computer, press Enter without typing to see the other systems, or choose one in the menu that comes after the passphrase.

  2. Sign in, and read the welcome

    The welcome opens on the first sign-in. It shows App Center, the themes, the AI you can turn on, updates and the shortcuts. Its Safety page has the two steps below. Both are also in Settings, under Security and sign-in.

  3. Make a recovery key

    A second way to unlock the disk, in case you forget the passphrase. It's shown once, for you to write down. Keep it away from the computer: anyone with the key and the computer can read your files.

  4. Turn Secure Boot back on, with your own keys

    ArashOS signs what starts the computer with keys made on it, and keeps Microsoft's, so Windows still starts. The computer has to be ready for new keys: Restart into firmware settings opens its settings, where you clear the Secure Boot keys (it may be called Reset to Setup Mode, Clear keys or Delete all keys) and keep Secure Boot off. Back in ArashOS, press Add keys, then turn Secure Boot on in the firmware settings. Settings says each step as you go.

If an update ever leaves the desktop not starting, choose ArashOS snapshots in the menu when the computer starts, and pick the copy from before it.