First boot

Singularity ships its own greeter, the login screen you can put in front of the desktop. It is optional: you enable it yourself, and until you do, you log in through whatever display manager your system already uses.

The greeter

The greeter lists the users on the system and lets you sign in. It is built on the same framework as the rest of the desktop, so it already looks like Singularity before you have logged in once.

Each user gets their own look on the login screen. The greeter reads your accent color and your wallpaper from the system account service, so the background you chose inside the desktop shows up, gently blurred, when you log in. Your avatar appears too, taken from your account picture.

Enabling the greeter

The greeter is optional, and installing Singularity does not replace your login manager with it. If you are happy with GDM, SDDM, or whatever you already use, keep it and pick the Singularity session there. To use the Singularity greeter instead, enable it yourself.

The greeter runs on greetd, so install greetd first (the package is greetd on Fedora, Arch, Debian, and Ubuntu). Then write the greetd session configuration:

make install-greeter

This sets up greetd to launch the Singularity greeter, but it does not change your active login manager. To switch over, disable your current one and enable greetd, then reboot:

sudo systemctl disable gdm
sudo systemctl enable greetd

On systems with SELinux in enforcing mode, greetd may be denied permission to run the greeter launcher scripts in /etc/greetd. make install-greeter already relabels them as executable; if the greeter still fails to start, confirm the labels with ls -Z /etc/greetd or, as a last resort, set SELinux to permissive while you investigate.

Choosing a session

If more than one desktop session is installed, the greeter lets you choose which one to start. It finds sessions the standard way, by scanning the usual system locations for installed session files, so anything installed correctly shows up in the list. Pick the Singularity session and sign in.

After login

The session launcher starts the compositor, then the shell, and keeps the desktop alive across restarts. The first thing you will see is the desktop: a panel at the top and a dock at the bottom.