Nothing here can leave you stranded

Three things stand behind everything else: a snapshot taken around every software change, a backup of your apps and settings that fits on a USB stick, and a disk that cannot be read out of this computer.

Before and afterA snapshot around every install, update and removal

From the boot menuStart from an old snapshot even when the computer will not start

One fileYour apps, their data and your settings, carried to another computer

Every install, update and removal sits between two snapshots.

Snapshots

When the system is on Btrfs, a snapshot of it is taken before and after every software change: installing, updating or removing anything from Debian or a software source. The work is done by snapper, the same tool other Linux systems use for this.

Settings, Snapshots lists them all. The camera button takes one now, which is what you want before trying something you may wish to undo.

Your files are not in them. When Roundel OS was put on with the Roundel Installer, your home folder has a part of the disk of its own and is left out of the snapshots, so restoring never touches your documents. Settings, Snapshots says so plainly if this computer is laid out differently.

Putting one back

Open Settings and choose Snapshots.Every snapshot is listed with what was happening when it was taken.
Press the restore arrow beside the one from before things went wrong.It asks a second time to be sure.
Restart.The system is as it was then. What it was a moment ago is set aside, not deleted, so you can change your mind.

Other systems on the disk keep their place in the boot menu, and the snapshots have an entry of their own.

If the computer will not start

Choose Roundel OS snapshots in the boot menu, then a snapshot. It starts as it was then, with a writable layer held in memory: nothing you do there is kept, so you can look round safely. If it is the one you want, restore it in Settings and it becomes the real system.

Other systems on the disk keep their own entries in the same menu, so a computer that dual boots still boots both.

Or drop to text. Ctrl, Alt and F2 gives an ordinary text login if the login screen itself fails. Ctrl, Alt and F7 goes back.

The Store's Move to another computer page: four switches and a button that saves one backup file.

Take your desktop with you

In the Store, choose Move to another computer. Switch on what to take: your apps, their own data, your AppImages and Roundel's settings. One backup file is made in your home folder. Copy it to a USB stick or to cloud storage.

On the other computer, open the same page, press the open button and choose the file. The apps are installed fresh from Flathub, and their data and your settings are put back. Log out and back in to see every setting.

Lightmorphic Flat makes the same kind of file, ending in .fmpack, so it can open a Roundel backup on any Linux computer, and a backup or app list made by Flat can be chosen here.

What goes in

The list of apps you have installed
Those apps' own settings and data
Your AppImages
Roundel's own settings

What does not

Your documents, pictures and other files
Wi-Fi passwords
Your GitHub key

Copy those over yourself. Apps already on the other computer keep their own settings; only the apps it installs get theirs back.

Why an update cannot strand you

Three kinds of update, each done in its own place, and each with a way back.

Apps from the Store

Open the Store and choose Updates, then press the update button. Flatpak apps are installed for you alone, so a broken app is yours to remove and cannot stop the computer starting.

Debian itself

In a terminal, sudo apt update then sudo apt upgrade. A snapshot is taken around it, so a bad kernel or driver is one restore away.

Roundel OS

A rolling release: improvements come as they are ready, each with its own number. In the folder you installed from, git pull then ./install.sh, and log out and back in.

Kept through all of it. Your settings, your apps and your files survive every update. Settings live outside the repository, in your own home folder: the keyboard and language in one file, the clock, wallpaper and idle times in another, your favourites in a third.

Roundel OS is tested on Debian stable, which is 13 at the time of writing. It has not been tested on Debian testing or unstable, and nothing can be promised about how it behaves there.

Settings, Snapshots: one taken before and one after each change, a camera to take one now, and a restore arrow beside each.

The two ways to unlock it

A passwordYou type it each time the computer starts, before anything else appears. Nothing but that password opens the disk, and nothing else needs to be trusted.

This computer's chipThe TPM chip opens the disk, so nothing is typed at start-up and the computer goes straight to the login screen. The password you chose is still your way back in if the board is replaced or the chip refuses.

NeitherYou can leave the disk unlocked. It starts a little quicker, and anyone who takes the drive out can read everything on it.

The installer can suggest a passphrase if you would rather not invent one. It has to be at least eight characters, and it is asked for twice.

A disk nobody else can read

The Roundel Installer offers to encrypt the whole disk, using LUKS, the standard Linux way of doing it. A locked disk cannot be read by anyone who takes it out of this computer.

This is the one choice that cannot be changed afterwards without installing again, so it is worth a moment on the installer's Privacy page rather than pressing Next.

Lose the password and the disk is gone. There is no spare key and nobody can recover it for you. Write it down and keep it somewhere safe.

The smaller safeguards

Things put in because they were needed, not because they made a list look longer.

A screen change undoes itself

Change the screen size and a message asks whether to keep it. Do nothing for fifteen seconds and it goes back, so a wrong choice never leaves you staring at nothing.

The system disk is never offered

Settings, Disks can wipe a USB stick, and asks twice. The drive the computer runs on is never in the list.

One part runs as root

Only roundel-admin does, through pkexec. It checks every argument it is given and reads passwords from standard input only.

The clipboard forgets

A password copied by mistake can be forgotten on its own, and the whole history clears itself on the schedule you chose.

A record of each session

Kept in .local/state/roundel/session.log in your home folder, which is what to look at, or attach to a bug report, when something went wrong.

Nothing phones home

No account, no telemetry and no check-in. The desktop reaches the network when you ask it to and not otherwise.

Ready to put it on a computer?

What you need, writing the image to a USB stick, and every question the Roundel Installer asks.

How to install it

Use at your own risk. Roundel OS is provided as is, with no warranty of any kind, and you use it entirely at your own risk. It changes how the computer starts, logs in and manages its disks. Back up everything that matters first.

The Roundel Installer's first page, with the mark at the start of a line of seven steps and boxes for language, keyboard and time