The Ubuntu vmimage requires specifying sudo - 1

build/tfs/linux/continuous-build-linux.yml

 steps:
 - script: |
     set -e
-    apt-get update
-    apt-get install -y libxkbfile-dev pkg-config libsecret-1-dev libxss1 libgconf-2-4 dbus xvfb libgtk-3-0
-    cp build/tfs/linux/x64/xvfb.init /etc/init.d/xvfb
-    chmod +x /etc/init.d/xvfb
-    update-rc.d xvfb defaults
-    ln -sf /bin/dbus-daemon /usr/bin/dbus-daemon
-    service xvfb start
-    service dbus start
+    sudo apt-get update
+    sudo apt-get install -y libxkbfile-dev pkg-config libsecret-1-dev libxss1 libgconf-2-4 dbus xvfb libgtk-3-0
+    sudo cp build/tfs/linux/x64/xvfb.init /etc/init.d/xvfb
+    sudo chmod +x /etc/init.d/xvfb
+    sudo update-rc.d xvfb defaults
+    sudo ln -sf /bin/dbus-daemon /usr/bin/dbus-daemon
+    sudo service xvfb start
+    sudo service dbus start
 - task: NodeTool@0
   inputs:
     versionSpec: "8.9.1"

build/tfs/linux/product-build-linux.yml

@@ -32,7 +32,7 @@ steps:
     npm run gulp -- "electron-$(VSCODE_ARCH)"
 
     # xvfb seems to be crashing often, let's make sure it's always up
-    service xvfb start
+    sudo service xvfb start
 
     DISPLAY=:10 ./scripts/test.sh --build --tfs "Unit Tests"
     # yarn smoketest -- --build "$(agent.builddirectory)/VSCode-linux-$(VSCODE_ARCH)"