LocalAI: pin the CPU backends when the container has no GPU runtime (#17909)

LocalAI resolves meta backends from the GPU vendor it reads out of sysfs,
which is the host's card even with no driver installed in the container,
so llama-cpp became cuda12-llama-cpp and never started (#17908). Force
the default capability unless a CUDA, ROCm or Level Zero runtime is
present; update adds the pin to existing installs.

ct/localai.sh

@@ -37,6 +37,15 @@ function update_script() {
     exit
   fi
 
+  # Older installs have no CPU pin; on a host with a GPU but no driver in the
+  # container every model then ends in "backend not found".
+  if ! grep -q '^LOCALAI_FORCE_META_BACKEND_CAPABILITY=' /opt/localai.env 2>/dev/null &&
+    ! ldconfig -p 2>/dev/null | grep -qE 'libcuda[.]so|libamdhip64[.]so|libze_intel_gpu[.]so|libze_loader[.]so'; then
+    echo "LOCALAI_FORCE_META_BACKEND_CAPABILITY=default" >>/opt/localai.env
+    systemctl restart localai
+    msg_ok "Pinned LocalAI to the CPU backends (no GPU runtime in the container)"
+  fi
+
   if check_for_gh_release "localai" "mudler/LocalAI"; then
     msg_info "Stopping Service"
     systemctl stop localai

install/localai-install.sh

@@ -39,6 +39,12 @@ LOCALAI_MODELS_PATH=/opt/localai_data/models
 LOCALAI_BACKENDS_PATH=/opt/localai_data/backends
 LOCALAI_LOG_LEVEL=info
 EOF
+# LocalAI picks the backend variant from the GPU it sees in sysfs, which is the
+# host's card even when no driver was installed in here, and a CUDA/ROCm/SYCL
+# backend then never starts. Pin the CPU variants unless a runtime is present.
+if ! ldconfig -p 2>/dev/null | grep -qE 'libcuda[.]so|libamdhip64[.]so|libze_intel_gpu[.]so|libze_loader[.]so'; then
+  echo "LOCALAI_FORCE_META_BACKEND_CAPABILITY=default" >>/opt/localai.env
+fi
 # LocalAI refuses to start on a wildcard bind with nothing to identify callers,
 # and binding the wildcard is what makes the container reachable at all.
 if [[ "$var_auth" == "yes" ]]; then