diff --git a/main/runner.sh b/main/runner.sh
index 5038ffb..6f88e1b 100644
--- a/main/runner.sh
+++ b/main/runner.sh
@@ -1,8 +1,10 @@
 #!/bin/bash
 # Copyright (c) 2022 fithwum
 # All rights reserved
+set -eu
 
 USER=fithwum
+FILE=config.yaml
 
 # openssh
 apt-get install openssh-client openssh-server
@@ -39,10 +41,50 @@ wget https://gitea.com/gitea/act_runner/releases/download/v0.2.13/act_runner-0.2
 mv act_runner-*-linux-amd64 act_runner
 chmod +x act_runner
 
-./act_runner generate-config | tee config.yaml > /dev/null
+./act_runner generate-config | tee $FILE > /dev/null
 chown fithwum:docker act_runner
-chown fithwum:docker config.yaml
-./act_runner --config config.yaml register
+chown fithwum:docker $FILE
+
+############################################################################################
+# Count label entries inside the labels block
+LABEL_COUNT=$(awk '
+  $0 ~ /^  labels:/ {in=1; next}
+  in && $0 ~ /^    - / {c++}
+  in && NF==0 {in=0}
+  END {print c+0}
+' "$FILE")
+
+if [ "$LABEL_COUNT" -ne 3 ]; then
+  echo "[ERROR] Expected exactly 3 labels, found $LABEL_COUNT. Aborting."
+  exit 1
+fi
+
+# Verify expected existing labels
+awk '
+  $0 ~ /^  labels:/ {in=1; next}
+  in && $0 ~ /^    - / {print}
+  in && NF==0 {exit}
+' "$FILE" | grep -qx '    - "vm-ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest"' \
+&& grep -qx '    - "vm-ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04"' \
+&& grep -qx '    - "vm-ubuntu-20.04:docker://docker.gitea.com/runner-images:ubuntu-20.04"' \
+|| {
+  echo "[ERROR] Existing labels do not match expected values. Aborting."
+  exit 1
+}
+
+# Replace block
+sed -i '/^  labels:/,/^$/c\
+  labels:\n\
+    - "vm-ubuntu-latest:docker://docker.gitea.com/runner-images:ubuntu-latest"\n\
+    - "vm-ubuntu-22.04:docker://docker.gitea.com/runner-images:ubuntu-22.04"\n\
+    - "vm-ubuntu-20.04:docker://docker.gitea.com/runner-images:ubuntu-20.04"\n\
+    - "vm-docker-build:docker://catthehacker/ubuntu:custom-latest-20240215"\n\
+    - "vm-docker-build2:docker://catthehacker/ubuntu:act-latest"' "$FILE"
+
+echo "[OK] labels block updated safely."
+############################################################################################
+
+./act_runner --config $FILE register
 
 ./act_runner register --no-interactive --instance <instance_url> --token <registration_token> --name <runner_name>
 
@@ -53,7 +95,7 @@ Documentation=https://gitea.com/gitea/act_runner
 After=docker.service
 
 [Service]
-ExecStart=/usr/local/bin/act_runner daemon --config /usr/local/bin/config.yaml
+ExecStart=/usr/local/bin/act_runner daemon --config /usr/local/bin/$FILE
 ExecReload=/bin/kill -s HUP $MAINPID
 WorkingDirectory=/usr/local/bin
 TimeoutSec=0