cosmic-trixie

The COSMIC desktop environment (System76), built from source as Debian packages for Debian 13 (trixie) stable.

COSMIC will never ship in trixie's official archive — a released Debian stable never gains new packages. This repo fills that gap: the whole cosmic-epoch stack compiled in a clean trixie container and split into proper Debian packages, so you can apt install cosmic-desktop on Debian 13.

Not affiliated with System76. Unofficial community packaging. The build tooling lives in deb-builders under cosmic-desktop/.

cosmic-trixie has moved home. The canonical repository now lives on Butterforge, our self-hosted forge. The old Codeberg address keeps working — it is now an automatically-synced mirror and will stay up for the foreseeable future. Nothing breaks if you do nothing. If you set this repo up before the move, see Migrating from the Codeberg address.

Available Packages

Package	Version	Description
cosmic-desktop	1.6.0	Full COSMIC desktop (metapackage)
cosmic-edit	1.6.0	Text editor
cosmic-files	1.6.0	File manager
cosmic-greeter	1.6.0	Greeter / login manager (greetd-based)
cosmic-icons	1.6.0	COSMIC icon theme
cosmic-monitor	1.6.0	System monitor
cosmic-player	1.6.0	Media player
cosmic-screenshot	1.6.0	Screenshot tool
cosmic-session	1.6.0	Session core: compositor, panel, applets, settings, daemon
cosmic-sound-theme	1.6.0	COSMIC sound theme
cosmic-store	1.6.0	App store
cosmic-term	1.6.0	Terminal emulator
cosmic-wallpapers	1.6.0	Default COSMIC wallpapers

cosmic-desktop is the metapackage that pulls in the whole desktop. Install just the pieces you want for a minimal setup.

Installation

1. Add the repository

# Add the repository signing key (armored .asc — apt reads it directly, no gnupg)
sudo curl -fsSL https://apt.justaguy.dev/cosmic-trixie/key.asc -o /usr/share/keyrings/cosmic-trixie.asc

# Add the repository to sources (one line)
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/cosmic-trixie.asc] https://apt.justaguy.dev/cosmic-trixie trixie main" | sudo tee /etc/apt/sources.list.d/cosmic-trixie.list

sudo apt update

2. Install COSMIC

# The whole desktop:
sudo apt install cosmic-desktop

# …or pick individual pieces:
sudo apt install cosmic-session cosmic-term cosmic-files

3. Log in to COSMIC

Log out, then pick "COSMIC" from your display manager's session menu — or run start-cosmic from a TTY.

Using LightDM? COSMIC may fail to start from LightDM and bounce you back to the login screen (see Known issues). The COSMIC greeter works better, with fewer issues — see below.

The COSMIC greeter (login manager): cosmic-greeter registers with Debian's display-manager system via debconf, like gdm3/lightdm/sddm. On install you're asked which login manager to use (or, if no other DM is registered, whether COSMIC should become your login manager — answering no leaves your current login method untouched). To switch to or away from the COSMIC greeter later, it's the standard:

sudo dpkg-reconfigure cosmic-greeter

This is fully reversible — your previous DM stays installed, and your other desktops still appear in the COSMIC greeter's session picker.

Updates

sudo apt update && sudo apt upgrade

Migrating from the Codeberg address

If your sources file points at justaguylinux.codeberg.page, that address still works and continues to receive every update — the mirror syncs automatically on every push. When you're ready to switch to the canonical address (same packages, same signing key, only the URL changes):

sudo sed -i 's|https://justaguylinux.codeberg.page/cosmic-trixie|https://apt.justaguy.dev/cosmic-trixie|' /etc/apt/sources.list.d/cosmic-trixie.list
sudo apt update

Prefer a script you can read first? migrate.sh in this repository does exactly the above (with a backup of your sources file) and nothing else.

Requirements

• Debian 13 (trixie), amd64. Built against trixie's libraries; not intended for Sid/testing (use debian-cosmic for those) or for Debian 12.
• A real GPU / DRM. In a VM, enable 3D acceleration (virtio-gpu + virgl/venus), or cosmic-comp may fail to start.

GPU drivers

cosmic-desktop pulls the Mesa stack (Intel / AMD / most GPUs) automatically as a Recommends — nothing to do. The compositor talks to whatever GPU backend is present through the vendor-neutral GLVND libraries (a hard dependency), so the driver is swappable.

NVIDIA (proprietary): the driver is non-free and a DKMS kernel module, so — as on any Debian system — you install it yourself. Enable contrib + non-free + non-free-firmware in your apt sources, then:

sudo apt install nvidia-detect      # confirms the right driver for your card
sudo apt install nvidia-driver
sudo reboot

COSMIC then uses the NVIDIA GPU automatically (GLVND loads NVIDIA's backend instead of Mesa) — no COSMIC-specific change, and no separate "NVIDIA edition" of this repo.

Known issues

COSMIC session won't start from LightDM

Picking COSMIC from LightDM's session menu can dump you straight back to the greeter, with xrdb / xhost "can't open display" errors in ~/.xsession-errors — LightDM pushes Wayland sessions through X11 session machinery. The fix: switch to the COSMIC greeter (see step 3). It handles Wayland sessions natively, works better with fewer issues, and still lists your other installed DEs/WMs.

pkexec GUI apps (Timeshift, GParted, …) fail with "cannot open display"

Fixed in 1.5.0-1 — just sudo apt upgrade, then log out and back in.

On older versions, a GUI tool that elevates through pkexec (e.g. Timeshift's timeshift-launcher) shows the password prompt and then nothing; run from a terminal it prints cannot open display. pkexec strips the Wayland environment, so the app runs as root over X11 — but the session had no Xwayland, and even with it present root wasn't allowed to connect. Since 1.5.0-1, cosmic-session depends on xwayland and grants root access to the session's Xwayland display at login (not a security regression — root already has full access to the machine). The manual equivalent on older packages:

sudo apt install xwayland x11-xserver-utils   # then log out and back in
xhost +si:localuser:root                      # per session

Duplicate polkit authentication agent

If another desktop's polkit agent is installed (lxpolkit, polkit-gnome, mate-polkit, xfce-polkit…), it autostarts in COSMIC too and races COSMIC's own agent, producing:

org.freedesktop.PolicyKit1.Error.Failed:
An authentication agent already exists for the given subject

Stop the foreign agent in COSMIC only (keeps it in your other sessions). For lxpolkit:

mkdir -p ~/.config/autostart
cp /etc/xdg/autostart/lxpolkit.desktop ~/.config/autostart/
printf 'NotShowIn=COSMIC;\n' >> ~/.config/autostart/lxpolkit.desktop

Log out of COSMIC and back in. Don't purge the agent package — that breaks polkit prompts in your other desktop/WM sessions.

Uninstallation

sudo apt remove cosmic-desktop 'cosmic-*'
sudo rm /etc/apt/sources.list.d/cosmic-trixie.list
sudo rm /usr/share/keyrings/cosmic-trixie.asc
sudo apt update

About

Unofficial, from-source packaging of COSMIC for Debian 13 stable. COSMIC is GPL-3.0; the packaging here is GPL-2.0 (see LICENSE). Wallpapers and icons carry their own (Creative Commons) terms upstream.

• COSMIC: https://github.com/pop-os/cosmic-epoch
• System76: https://system76.com

Privacy

Signed static files over HTTPS — no tracking, no analytics, no download logs. (The forge's web pages use self-hosted, cookieless Umami for aggregate page counts; it never runs on the apt endpoints.) Served from our own infrastructure (Butterforge) with access logging disabled by policy; the exact web-server configuration is published in butterrepo's docs/apt-vhost.Caddyfile (one server block serves both repos). The Codeberg mirror is governed by Codeberg's Privacy Policy, as before.

Support

Connect

• YouTube — tutorials and guides
• Butterforge — source code and projects
• The Butter Lab — Discourse forum
• The Churn — community chat (Fluxer)
• Wiki — documentation and guides
• Mastodon — @justaguylinux@fosstodon.org
• Butterbian — a Debian-based distro

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