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SDDM on Wayland + Sway (openSUSE)

SDDM is a system-level component — its config lives in /etc/ and /var/lib/sddm/, not in userspace dotfiles. Dotbot cannot manage these paths. Automation must be handled via a dedicated script with sudo.

How it works

/etc/sddm.conf sets CompositorCommand=sway, meaning SDDM launches Sway as its Wayland greeter compositor. It runs under the sddm system user, whose home is /var/lib/sddm/.

The SDDM Sway session is completely isolated from the regular user session:

  • it never reads ~/.config/sway/config
  • it never runs kanshi or any user services
  • output configuration (rotation, resolution) must be declared in the sddm user's own Sway config

Active config on this machine

/etc/sddm.conf

[Theme]
Current=silent

[General]
InputMethod=qtvirtualkeyboard
GreeterEnvironment=QML2_IMPORT_PATH=/usr/share/sddm/themes/silent/components/,QT_IM_MODULE=qtvirtualkeyboard,QT_WAYLAND_SHELL_INTEGRATION=layer-shell
DisplayServer=wayland

[Wayland]
EnableHiDPI=true
CompositorCommand=sway

/etc/sddm.conf.d/10-wayland.conf

[General]
DisplayServer=wayland
GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell

[Wayland]
EnableHiDPI=true
CompositorCommand=XDG_SESSION_TYPE=wayland XDG_CURRENT_DESKTOP=sway sway

Note: sddm.conf.d/ snippets are merged. The 10-wayland.conf snippet sets a more explicit CompositorCommand with env vars. This takes precedence per snippet ordering.

Output rotation at the greeter

The HDMI-A-2 ($DELL) display requires transform 90 (as seen in kanshi config). Without a sddm-user sway config this transform is not applied at the login screen.

Manual setup

# 1. Create the config dir for the sddm user
sudo mkdir -p /var/lib/sddm/.config/sway

# 2. Write a minimal sway config with output rotation
sudo tee /var/lib/sddm/.config/sway/config <<'EOF'
# SDDM greeter sway config
# Managed by: scripts/opensuse/03-sddm.sh
# Do NOT edit manually — re-run the script instead.

xwayland disable

output HDMI-A-1 {
    mode 3840x2160
    pos 0 0
}

output HDMI-A-2 {
    mode 2560x1440@120hz
    transform 90
    pos 3840 0
}
EOF

# 3. Fix ownership
sudo chown -R sddm:sddm /var/lib/sddm/.config/

# 4. Restart SDDM
sudo systemctl restart sddm

Find output names (from a running Sway session)

swaymsg -t get_outputs | grep name
# or check kanshi config:
cat ~/.config/kanshi/config

Automation

All of the above is automated in scripts/opensuse/03-sddm.sh. Run it after the base package install step:

just opensuse-sddm

The script is idempotent — safe to re-run.

Troubleshooting

Symptom Cause Fix
Login screen shows on wrong/rotated display No sddm sway config Run 03-sddm.sh
SDDM fails to start Wayland session CompositorCommand missing sway in PATH Check /etc/sddm.conf.d/ ordering
Theme not loading /usr/share/sddm/themes/silent missing sudo zypper in sddm-theme-silent (or equivalent)
Changes not applied after edit SDDM already running sudo systemctl restart sddm

Why not Dotbot?

Dotbot symlinks files into ~ (the calling user's home). Paths under /etc/ and /var/lib/sddm/ require sudo and belong to a different user (sddm). A shell script with explicit sudo commands is the right tool for system-level config like this.