Scan backends

Set the backend in Preferences → Scanner Settings or scan_backend in settings.json.

Backend	Startup	Idle memory	Use it when
Auto (default)	daemon if reachable; otherwise clamscan	about 50 MB without daemon	Most desktops
Daemon	immediate	500 MB–1 GB for clamd	Frequent, scheduled, or performance-sensitive scans
Clamscan	loads definitions each scan (about 3–10 seconds)	about 50 MB	Occasional scans, minimal setup, or daemon diagnosis

Auto checks clamdscan --ping and caches availability for 60 seconds. Daemon mode uses --multiscan and --fdpass; scans fail when the daemon is down. clamscan has no background service and forwards relevant clamd.conf limits (MaxFileSize, MaxScanSize, MaxRecursion, and MaxFiles) as CLI limits so both modes remain consistent.

Install a daemon

# Debian/Ubuntu
sudo apt install clamav-daemon
sudo systemctl enable --now clamav-daemon
clamdscan --version

# Fedora
sudo dnf install clamd clamav-freshclam
sudo freshclam
sudo systemctl enable --now clamd@scan

# Arch Linux
sudo pacman -S clamav
sudo systemctl enable --now clamav-daemon

Fedora uses /etc/clamd.d/scan.conf; ClamUI invokes clamdscan --config-file=/etc/clamd.d/scan.conf. If a running Fedora daemon is unavailable, check its LocalSocketMode and LocalSocketGroup.

Flatpak users install all ClamAV tools on the host. ClamUI invokes them through flatpak-spawn --host and auto-detects the host daemon.

Sockets and exit codes

ClamUI probes /var/run/clamav/clamd.ctl, /run/clamav/clamd.ctl, /run/clamd.scan/clamd.sock, and /var/run/clamd.scan/clamd.sock, after checking configured LocalSocket. Override with daemon_socket_path when necessary.

grep "LocalSocket" /etc/clamav/clamd.conf
grep "LocalSocket" /etc/clamd.d/scan.conf

Both modes use standard ClamAV codes: 0 clean, 1 detection, and 2 error. See Configuration for overrides and Troubleshooting for failures.