Early release

Download Atrium

Two installers for the same Atrium. Either one looks at the graphics card and chooses one of three systems by itself. Atrium is free.

Both files come from a small line, a few downloads at a time. If you get "Too Many Requests", try again later. A stopped download can be resumed.

What to know about the small installer

It holds no system. It chooses between the three systems the same way as the large one, and the steps below are the same, except for what is listed here.

• We have used it on virtual test machines only, and only with a network cable. The installer has a network screen. Whether it can join a Wi-Fi network we have not tried.
• "Begin Installation" stays grey until the installer has a connection. If you plug the cable in after the installer has started, click "Network & Host Name" once and press "Done".
• After "Begin Installation" the disk is erased first, and then the system is downloaded. The screen shows one line, "Deployment starting", and a bar that does not move. In our tests it took between 18 and 53 minutes. Yours depends on your line and on how many others are downloading. Before you press it, be sure this connection really reaches the internet: a network that first asks for a login in a browser will not work.
• If the installer cannot reach our server at that point, a window says so about a minute later and offers "Try again". The cause can be your connection, or our server being busy or away. Check the connection, wait a few minutes, and press it: the install carries on. If it never works, hold the power button to switch off. The disk is already erased by then. Start again from the stick later, or use the large installer.
• If the connection drops during the download, the screen does not change. In our test the download carried on by itself when the connection came back after six minutes. If it does not come back, the PC is left without a system: hold the power button to switch off, and start the installer again from the stick.
• The system comes from the same small line as the files above. We have tried three installs at once, two of them from one home: all three finished, each slower than alone. With more, the server turns some away for a while.

Before you install

• Installing erases the whole disk you install Atrium on: the system that is on it now, your programs and your files. It cannot be undone. Copy everything you want to keep off that disk first.
• This is an early release. So far Atrium runs on virtual test machines and on one real laptop with Intel graphics, and we have used both installers only on virtual machines. Expect rough edges.
• If the PC has an NVIDIA graphics card that NVIDIA's drivers still support (about the GTX 900 series and newer), the installer chooses a system with NVIDIA's driver. An older NVIDIA card gets the standard system. Our test machines have no NVIDIA card: we have seen neither that choice nor those systems on a real card yet.
• Some multiplayer games refuse to start on Linux systems because of their anti-cheat. Check the games you cannot do without before you switch.
• Atrium signs in to your account by itself when the PC starts. Anyone who can switch the PC on gets your desktop and your signed-in apps.
• Atrium is free. It comes as it is, without a warranty, as far as the law allows. You install it at your own risk.
• If the PC is not yours, or you are under 18, ask the person it belongs to first. A 24HG account needs you to be 13 or older.

What you need

• A 64-bit PC with an Intel or AMD processor.
• A USB stick of 16 GB or more, or of 2 GB or more for the small installer. Everything on it is erased.
• An internet connection after installing, for updates, the standard apps and Steam. The small installer needs it while installing too.

Our test machines run Atrium with 6 GB of memory and a 40 GB disk. A PC for games needs more of both. We have not measured a minimum yet, and we would rather measure it than guess.

How to install

1. Write the file to the USB stick. Use Fedora Media Writer, a free program for Windows, macOS and Linux: "Select .iso file", pick the file you downloaded, pick the stick, press "Write".
2. Start the PC from the stick. Switch the PC on and press its boot-menu key at once (F12 on most PCs; Esc, F8 or F9 on others). Choose the USB stick, then "Install Atrium 44". The number is the version of the system underneath.
3. Pick your language. It becomes the language of the installed system.
4. Create your account. On the summary screen click "User Creation", type your name and a password, and press "Done".
5. Choose the disk. Click "Installation Destination", choose the disk and press "Done". If a box says there is not enough space, press "Reclaim space", "Delete all", "Reclaim space". This is the step that erases the disk. If the PC has more than one disk, tick only the one for Atrium: every ticked disk is erased. If you are not sure, unplug the others first.
6. Press "Begin Installation". On our test machines the bar stands still for about 15 to 35 minutes while the system is copied. When it says "Complete!", press "Reboot System" and pull the stick out.
7. Confirm the key on the blue screen. Once, right after installing, a blue screen titled "Perform MOK management" asks whether the PC may trust the system. Do not press Enter straight away: the first line, "Continue boot", is the wrong one. Go down to "Enroll MOK" and press Enter, then "Continue", then "Yes", type universalblue and press Enter, then "Reboot".
8. Atrium starts by itself. The standard apps install in the background, which takes about 10 to 15 minutes on our test machines. Sign in to 24HG and to Steam from the welcome page.

The blue screen is Secure Boot, a safety feature of the PC. The key belongs to the system Atrium is built on. It is stored in the PC and stays there if you remove Atrium later; from then on the PC trusts software signed with that key until you remove the key. The word universalblue is the same for everyone and is not a secret. If no blue screen appears, Secure Boot is switched off on that PC or the key is already stored from an earlier install, and Atrium starts without it. If you pressed "Continue boot" by mistake, Atrium will not start: install it again and choose "Enroll MOK", or switch Secure Boot off in the PC's set-up.

Atrium on a USB drive

Atrium can be installed onto a USB drive in place of the disk inside the PC. It is a full install, onto the drive. Our test machine then started Atrium from the drive by itself. If your PC starts its own system instead, choose the drive with the boot-menu key, as in step 2. It is meant for trying Atrium on a PC whose disk you do not want to change. Copy what you cannot lose off that disk first all the same: one wrong tick in step 5 erases it.

• You need a second USB drive for Atrium itself, 64 GB or more, beside the stick that holds the installer. Everything on it is erased. The one we tried held 34 GB; a drive sold as 32 GB holds less and we have not tried one.
• In step 5 tick only that drive. The installer ticks no disk by itself, and it says of the others: "Disks left unselected here will not be touched." Read the size above each disk before you press "Done", because the disk you tick is erased. If the "Reclaim space" window of step 5 appears, it must list only that drive before you press "Delete all". Our test drive was empty, so we have not seen that window with a second disk in the machine.
• Two things that we know of are stored in the PC itself, not on its disk. One is a start entry, placed first in the PC's start order and called "Bazzite", after the system Atrium is built on. The other, if Secure Boot is on, is the key from the blue screen. The key stays when you pull the drive out; the start entry stayed in our test machine.
• While it runs, Atrium opens a partition on another disk by itself if it holds a Linux file system (ext4 or btrfs) with a name, and then it can write there. It did not open the Windows-style partitions of our test disk.
• Windows encrypts the disk of many PCs without asking (BitLocker, or "Device encryption" in its settings). Look there before you start and have the recovery key at hand: Windows may ask for it the next time it starts, above all if you switch Secure Boot off. We have not tried this on such a PC.
• Windows may show the wrong time once afterwards, because the two systems keep the PC's clock in different ways. We have not checked this.

What we have seen, on one virtual test machine with a USB drive and a second disk laid out the way Windows lays one out, with files on it: the install took 24 minutes; the machine then started Atrium from the USB drive; and every byte of the other disk was the same afterwards as before, once after the install and once more after Atrium had run and been shut down. With the drive pulled out, the machine went on to the next thing it could start. That disk held no Windows that starts, and none of this has been done on a real PC yet. We have not watched a PC start Windows again with the drive out. If yours does not, choose "Windows Boot Manager" with the boot-menu key. We have not tried removing the start entry or the key. How long the install takes on a real USB stick, and how fast Atrium is from one, we have not measured.

What is not finished

• If the PC had no network cable while installing, the clock can show the wrong time zone afterwards. Atrium says so once after the first sign-in. Set yours in System Settings, under Date & Time.
• The installer is the one of the system Atrium is built on, and it says "Atrium 44". Both installers show our logo and colours.
• A PC installed with the first installer, the one offered on 9 October 2026, is called "bazzite" on the network, the name of the system Atrium is built on. A PC installed from today's files is called "atrium".
• On a PC that still runs a build older than 20261010d, do not type or play while Check for updates is working: when a new version is ready its window takes the keyboard, and Enter then means "Restart now". A test PC of ours restarted that way on 10 October 2026. From build 20261010d on, a stray key means "Later". An update that arrives by itself never restarts the PC.
• The App Store button opens the store of the system underneath. It opens on Flathub's own page; our picks are under the store's tab "Curated".
• The large installer holds build 20261010d. After installing, Atrium starts fetching the newest build by itself within about an hour of a start, or at once when you press Check for updates; it takes effect at the next restart. The small installer installs the newest build straight away.

What Atrium sends

Atrium asks our update server whether there is a new version, and downloads it. We count how many of these requests arrive each day, from a log that does not hold your internet address. The requests reach us through Cloudflare, which carries our traffic and sees your address as it does for any website.

Once a week Atrium sends a small count to Fedora and to the other software sources that ask to be counted. It comes from the Fedora system underneath and is on from the first start. It says which system and version the PC runs, the processor type and roughly how old the installation is, with no name and no ID; like any request it arrives from your internet address. Fedora publishes the totals and we read the figure for Atrium. To switch it off, open "Privacy and reports" in the application list; the full text is there.

Atrium installs its standard apps by itself at the first start, and again when a new version of Atrium adds one. They come from Flathub, the app source of the system underneath, and so do their updates. From build 20261010b on, one of them is Mojang's Minecraft launcher, in a package made by the Flathub community and not by Mojang. That package fetches the launcher from Mojang, a Microsoft company, while it installs. Flathub and Mojang see your internet address and what is fetched, as with any download. Any of these apps can be removed, and a removed app is not brought back.

Atrium has no program that reports to 24HG about you or your computer by itself. The 24HG window shows our website. Like any website it sees and counts your visits, and on Atrium it can read a few things from the PC: the Atrium version and which Steam games are installed, so the Games page can show them, and, from build 20261010f on, which of our three systems it is, the graphics card's name and a memory range, for the Send feedback page. Once they are running, Steam, Discord, the Minecraft launchers, the browser and the system underneath make connections of their own. We do not control those and have not listed them yet.

"Send feedback", in the application list from build 20261010f on, opens a page of our website. Nothing is sent until you press Send. The page shows the build, which of our three systems it is, the graphics card and a memory range; they are attached to your message only if you tick their box, and your account goes along only if you tick its own box. We delete messages after 12 months.

The website's privacy policy has a section on Atrium, and "Privacy and reports" on the PC lists what Atrium sends. Atrium is made by 24HG; questions go to the address on that policy or to the Discord.

Checking the download

You do not have to. If you want to be sure the file arrived whole, work out its SHA-256 and compare it with the value in that installer's box at the top of this page. On Windows, in PowerShell: Get-FileHash atrium-20261010d.iso. On Linux: sha256sum atrium-20261010d.iso. On macOS: shasum -a 256 atrium-20261010d.iso. The same value is in a small file beside the installer. For the small installer the file name is atrium-online-r4.iso. It has a value of its own, shown in its box, and its own small file.

If something goes wrong

Tell us on the Discord, with the make of the PC and what you saw. The roadmap shows what is done and what is left.