diff --git a/.github/workflows/test-user_option.yml b/.github/workflows/test-user_option.yml
new file mode 100644
index 0000000..a9b7d6b
--- /dev/null
+++ b/.github/workflows/test-user_option.yml
@@ -0,0 +1,48 @@
+name: Test user option
+on:
+  push:
+    branches:
+      - 'main'
+      - 'releases/**'
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - run: |
+        id | grep -c runner
+    - uses: actions/checkout@v3
+    - uses: ./ # pguyot/arm-runner-action@HEAD
+      with:
+        commands: |
+          id | grep -c root
+    - uses: ./ # pguyot/arm-runner-action@HEAD
+      with:
+        user: nobody
+        commands: |
+          id | grep -c nobody
+    - uses: ./ # pguyot/arm-runner-action@HEAD
+      with:
+        user: nobody:lp
+        commands: |
+          id | grep -c lp
+    - uses: ./ # pguyot/arm-runner-action@HEAD
+      with:
+        user: nobody
+        use_systemd_nspawn: true
+        commands: |
+          id | grep -c nobody
+    - id: unknown_user
+      continue-on-error: true
+      uses: ./ # pguyot/arm-runner-action@HEAD
+      with:
+        user: unknown_user
+        commands: |
+          id
+    - name: Report unexpected success
+      if: ${{ steps.unknown_user.outcome == 'success' }}
+      run: |
+        echo "Action is expected to fail"
+        exit 1
diff --git a/README.md b/README.md
index f9f0332..327f33c 100644
--- a/README.md
+++ b/README.md
@@ -240,6 +240,13 @@ with some shells that come packaged under a different package name.
 For example, to use `ksh93` as shell, set `shell` to `ksh93` and
 `shell_package` to `ksh`.
 
+#### `user`
+
+User to run commands within the image. It must exists.
+By default, commands are run with user 0 (root).
+Unless you are using `systemd-nspawn`, you can also specify the group with
+the `user:group` syntax.
+
 #### `exit_on_fail`
 
 Exit immediately if a command exits with a non-zero status. Default is to exit.
diff --git a/action.yml b/action.yml
index bc471c6..b687e7c 100644
--- a/action.yml
+++ b/action.yml
@@ -64,6 +64,10 @@ inputs:
     description: 'The shell package to install, if different from shell'
     required: false
     default: ''
+  user:
+    description: 'User to run commands on the image. Must exist in the image'
+    required: false
+    default: ''
   exit_on_fail:
     description: 'Exit immediately if a command exits with a non-zero status'
     required: false
@@ -178,6 +182,15 @@ runs:
         else
             shell_opts=""
         fi
+        if [ "${{ inputs.user }}" != "" ]; then
+            if [ "${{ inputs.use_systemd_nspawn }}x" != "x" -a "${{ inputs.use_systemd_nspawn }}x" != "nox" ]; then
+                user_opt="-u ${{ inputs.user }}"
+            else
+                user_opt="--userspec=${{ inputs.user }}"
+            fi
+        else
+            user_opt=""
+        fi
         shell_package=${{ inputs.shell_package }}
         [ -x ${{ steps.mount_image.outputs.mount }}/${shell} ] || \
         shell_path=$(sudo chroot ${{ steps.mount_image.outputs.mount }} /bin/sh -c "command -v ${shell}") || \
@@ -233,9 +246,9 @@ runs:
         ARM_RUNNER_INPUT_COMMANDS_EOF
         if [ "${{ inputs.use_systemd_nspawn }}x" != "x" -a "${{ inputs.use_systemd_nspawn }}x" != "nox" ]; then
             sudo apt-get install -y systemd-container
-            sudo -E systemd-nspawn -q -a --bind=${script_dir}:${chroot_script_dir} -D ${{ steps.mount_image.outputs.mount }} ${{ inputs.systemd_nspawn_options }} ${shell_path} ${shell_opts} ${chroot_script_dir}/commands.sh
+            sudo -E systemd-nspawn ${user_opt} -q -a --bind=${script_dir}:${chroot_script_dir} -D ${{ steps.mount_image.outputs.mount }} ${{ inputs.systemd_nspawn_options }} ${shell_path} ${shell_opts} ${chroot_script_dir}/commands.sh
         else
-            sudo -E chroot ${{ steps.mount_image.outputs.mount }} ${shell_path} ${shell_opts} ${chroot_script_dir}/commands.sh
+            sudo -E chroot ${user_opt} ${{ steps.mount_image.outputs.mount }} ${shell_path} ${shell_opts} ${chroot_script_dir}/commands.sh
         fi
         rc=$?
         [ -f ${script_dir}/github_env.sh ] && \
@@ -244,7 +257,7 @@ runs:
       shell: bash
     - name: Copy artifacts within image
       if: ${{ always() && !cancelled() && (inputs.copy_artifacts_on_fail == 'yes' || steps.runcmd.conclusion == 'success') }}
-       run: |
+      run: |
         case "${{ inputs.debug }}" in
         yes|true)
             set -x