diff --git a/src/_common/README.md b/src/_common/README.md
new file mode 100644
index 000000000..64ea15c66
--- /dev/null
+++ b/src/_common/README.md
@@ -0,0 +1,122 @@
+# Common Helper Scripts
+
+This directory contains common helper scripts that can be shared across multiple features to avoid code duplication.
+
+## common-setup.sh
+
+A helper script that provides common setup functions used across multiple features.
+
+### Functions
+
+#### `determine_user_from_input`
+
+Determines the appropriate non-root user based on the input username.
+
+**Usage:**
+```bash
+# Source the helper script
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
+# Determine the user
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
+```
+
+**Parameters:**
+- `$1` (required): Input username from feature configuration (e.g., "automatic", "auto", "none", or a specific username)
+- `$2` (optional): Fallback username when no user is found in automatic mode (defaults to "root")
+
+**Behavior:**
+- **"auto" or "automatic"**: 
+  - First checks if `_REMOTE_USER` environment variable is set and is not "root"
+  - If `_REMOTE_USER` is root or not set, searches for an existing user from the priority list:
+    1. `devcontainer`
+    2. `vscode`
+    3. `node`
+    4. `codespace`
+    5. User with UID 1000 (from `/etc/passwd`)
+  - If no user is found, returns the fallback user (default: "root")
+  
+- **"none"**: Always returns "root"
+
+- **Specific username**: 
+  - Validates the user exists using `id -u`
+  - If the user exists, returns that username
+  - If the user doesn't exist, returns "root"
+
+**Examples:**
+
+```bash
+# Basic usage with default fallback (root)
+USERNAME=$(determine_user_from_input "automatic")
+
+# With custom fallback
+USERNAME=$(determine_user_from_input "automatic" "vscode")
+
+# Explicit user
+USERNAME=$(determine_user_from_input "myuser")
+
+# None (always returns root)
+USERNAME=$(determine_user_from_input "none")
+```
+
+**Return Value:**
+Prints the resolved username to stdout, which can be captured using command substitution.
+
+## Testing
+
+Tests for the helper scripts are located in `/test/_common/`. Run the tests with:
+
+```bash
+bash test/_common/test-common-setup.sh
+```
+
+## Edge Cases
+
+The helper handles several edge cases:
+
+1. **Missing awk**: Some systems (like Mariner) don't have awk by default. Features should install it before sourcing the helper if needed.
+
+2. **UID 1000 lookup**: The user with UID 1000 is included in the search as it's commonly the first non-system user created.
+
+3. **_REMOTE_USER behavior**: When `_REMOTE_USER` is set to a non-root user, it takes priority over all other detection methods in automatic mode.
+
+4. **Empty user list entries**: The helper safely handles empty entries in the user detection loop.
+
+## Migration Guide
+
+To migrate an existing feature to use the common helper:
+
+### Before:
+```bash
+# Determine the appropriate non-root user
+if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
+    USERNAME=""
+    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
+    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
+        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
+            USERNAME=${CURRENT_USER}
+            break
+        fi
+    done
+    if [ "${USERNAME}" = "" ]; then
+        USERNAME=root
+    fi
+elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
+    USERNAME=root
+fi
+```
+
+### After:
+```bash
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
+# Determine the appropriate non-root user
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
+```
+
+**Note:** For features like `common-utils` that create users and need a different fallback, use:
+```bash
+USERNAME=$(determine_user_from_input "${USERNAME}" "vscode")
+```
diff --git a/src/_common/common-setup.sh b/src/_common/common-setup.sh
new file mode 100644
index 000000000..d2ac866cf
--- /dev/null
+++ b/src/_common/common-setup.sh
@@ -0,0 +1,87 @@
+#!/bin/bash
+#-------------------------------------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See https://github.com/devcontainers/features/blob/main/LICENSE for license information.
+#-------------------------------------------------------------------------------------------------------------------------
+#
+# Helper script for common feature setup tasks, including user selection logic.
+# Maintainer: The Dev Container spec maintainers
+
+# Determine the appropriate non-root user
+# Usage: determine_user_from_input USERNAME [FALLBACK_USER]
+#
+# This function resolves the USERNAME variable based on the input value:
+# - If USERNAME is "auto" or "automatic", it will detect an existing non-root user
+# - If USERNAME is "none" or doesn't exist, it will fall back to root
+# - Otherwise, it validates the specified USERNAME exists
+#
+# Arguments:
+#   USERNAME - The username input (typically from feature configuration)
+#   FALLBACK_USER - Optional fallback user when no user is found in automatic mode (defaults to "root")
+#
+# Returns:
+#   The resolved username is printed to stdout
+#
+# Examples:
+#   USERNAME=$(determine_user_from_input "automatic")
+#   USERNAME=$(determine_user_from_input "vscode")
+#   USERNAME=$(determine_user_from_input "auto" "vscode")
+#
+determine_user_from_input() {
+    local input_username="${1:-automatic}"
+    local fallback_user="${2:-root}"
+    local resolved_username=""
+
+    if [ "${input_username}" = "auto" ] || [ "${input_username}" = "automatic" ]; then
+        # Automatic mode: try to detect an existing non-root user
+        
+        # First, check if _REMOTE_USER is set and is not root
+        if [ -n "${_REMOTE_USER:-}" ] && [ "${_REMOTE_USER}" != "root" ]; then
+            # Verify the user exists before using it
+            if id -u "${_REMOTE_USER}" > /dev/null 2>&1; then
+                resolved_username="${_REMOTE_USER}"
+            else
+                # _REMOTE_USER doesn't exist, fall through to normal detection
+                resolved_username=""
+            fi
+        fi
+        
+        # If we didn't resolve via _REMOTE_USER, try to find a non-root user
+        if [ -z "${resolved_username}" ]; then
+            # Try to find a non-root user from a list of common usernames
+            # The list includes: devcontainer, vscode, node, codespace, and the user with UID 1000
+            local possible_users=("devcontainer" "vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')")
+            
+            for current_user in "${possible_users[@]}"; do
+                # Skip empty entries
+                if [ -z "${current_user}" ]; then
+                    continue
+                fi
+                
+                # Check if user exists
+                if id -u "${current_user}" > /dev/null 2>&1; then
+                    resolved_username="${current_user}"
+                    break
+                fi
+            done
+            
+            # If no user found, use the fallback
+            if [ -z "${resolved_username}" ]; then
+                resolved_username="${fallback_user}"
+            fi
+        fi
+    elif [ "${input_username}" = "none" ]; then
+        # Explicit "none" means use root
+        resolved_username="root"
+    else
+        # Specific username provided - validate it exists
+        if id -u "${input_username}" > /dev/null 2>&1; then
+            resolved_username="${input_username}"
+        else
+            # User doesn't exist, fall back to root
+            resolved_username="root"
+        fi
+    fi
+
+    echo "${resolved_username}"
+}
diff --git a/src/anaconda/install.sh b/src/anaconda/install.sh
index 6f57a3144..01b7b15ef 100755
--- a/src/anaconda/install.sh
+++ b/src/anaconda/install.sh
@@ -81,22 +81,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u "${CURRENT_USER}" > /dev/null 2>&1; then
-            USERNAME="${CURRENT_USER}"
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 architecture="$(uname -m)"
 # Normalize arm64 to aarch64 for consistency
diff --git a/src/common-utils/main.sh b/src/common-utils/main.sh
index b0fd2f3b0..eaa4cb512 100644
--- a/src/common-utils/main.sh
+++ b/src/common-utils/main.sh
@@ -399,27 +399,20 @@ case "${ADJUSTED_ID}" in
         ;;
 esac
 
-# If in automatic mode, determine if a user already exists, if not use vscode
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    if [ "${_REMOTE_USER}" != "root" ]; then
-        USERNAME="${_REMOTE_USER}"
-    else
-        USERNAME=""
-        POSSIBLE_USERS=("devcontainer" "vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-        for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-            if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-                USERNAME=${CURRENT_USER}
-                break
-            fi
-        done
-        if [ "${USERNAME}" = "" ]; then
-            USERNAME=vscode
-        fi
-    fi
-elif [ "${USERNAME}" = "none" ]; then
-    USERNAME=root
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
+# Handle the special "none" case for common-utils before user determination
+# The "none" case sets USER_UID and USER_GID to 0
+ORIGINAL_USERNAME="${USERNAME}"
+if [ "${ORIGINAL_USERNAME}" = "none" ]; then
+    USERNAME="root"
     USER_UID=0
     USER_GID=0
+else
+    # If in automatic mode, determine if a user already exists, if not use vscode (which will be created)
+    USERNAME=$(determine_user_from_input "${USERNAME}" "vscode")
 fi
 # Create or update a non-root user to match UID/GID.
 group_name="${USERNAME}"
diff --git a/src/conda/install.sh b/src/conda/install.sh
index 43ab82f54..20e4feeac 100644
--- a/src/conda/install.sh
+++ b/src/conda/install.sh
@@ -27,22 +27,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u "${CURRENT_USER}" > /dev/null 2>&1; then
-            USERNAME="${CURRENT_USER}"
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 architecture="$(uname -m)"
 if [ "${architecture}" != "x86_64" ]; then
diff --git a/src/desktop-lite/install.sh b/src/desktop-lite/install.sh
index 4575cc4f9..3f366b354 100755
--- a/src/desktop-lite/install.sh
+++ b/src/desktop-lite/install.sh
@@ -71,22 +71,12 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 # Add default Fluxbox config files if none are already present
 fluxbox_apps="$(cat \
 << 'EOF'
diff --git a/src/docker-in-docker/install.sh b/src/docker-in-docker/install.sh
index 3f30158e5..db365d394 100755
--- a/src/docker-in-docker/install.sh
+++ b/src/docker-in-docker/install.sh
@@ -44,22 +44,12 @@ fi
 # See: https://github.com/microsoft/vscode-dev-containers/blob/main/script-library/shared/utils.sh
 ###################
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 # Package manager update function
 pkg_mgr_update() {
diff --git a/src/docker-outside-of-docker/install.sh b/src/docker-outside-of-docker/install.sh
index 74fd63530..034dde234 100755
--- a/src/docker-outside-of-docker/install.sh
+++ b/src/docker-outside-of-docker/install.sh
@@ -38,22 +38,12 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 apt_get_update()
 {
diff --git a/src/go/install.sh b/src/go/install.sh
index 85fea5dc4..f4628b37e 100755
--- a/src/go/install.sh
+++ b/src/go/install.sh
@@ -174,22 +174,12 @@ if ! type awk >/dev/null 2>&1; then
     check_packages awk
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 export DEBIAN_FRONTEND=noninteractive
 
diff --git a/src/hugo/install.sh b/src/hugo/install.sh
index b268e384b..bbfd2bb13 100755
--- a/src/hugo/install.sh
+++ b/src/hugo/install.sh
@@ -29,22 +29,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 architecture="$(uname -m)"
 if [ "${architecture}" != "amd64" ] && [ "${architecture}" != "x86_64" ] && [ "${architecture}" != "arm64" ] && [ "${architecture}" != "aarch64" ]; then
diff --git a/src/java/install.sh b/src/java/install.sh
index 62fd39462..f1d13d201 100644
--- a/src/java/install.sh
+++ b/src/java/install.sh
@@ -154,22 +154,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 updaterc() {
     local _bashrc
diff --git a/src/java/wrapper.sh b/src/java/wrapper.sh
index bea343f96..202a1856d 100644
--- a/src/java/wrapper.sh
+++ b/src/java/wrapper.sh
@@ -23,19 +23,6 @@ if [ "${is_jdk_8}" = "true" ]; then
     ./install.sh "${ADDITIONAL_JAVA_VERSION}" "${SDKMAN_DIR}" "${USERNAME}" "${UPDATE_RC}"
     jdk_11_folder="$(ls --format=single-column ${SDKMAN_DIR}/candidates/java | grep -oE -m 1 '11\..+')"
     ln -s "${SDKMAN_DIR}/candidates/java/${jdk_11_folder}" /extension-java-home
-
-    # Determine the appropriate non-root user
-    username=""
-    possible_users=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for current_user in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${current_user} > /dev/null 2>&1; then
-            username=${current_user}
-            break
-        fi
-    done
-    if [ "${username}" = "" ]; then
-        username=root
-    fi
 else
     ln -s ${SDKMAN_DIR}/candidates/java/current /extension-java-home
 fi
diff --git a/src/kubectl-helm-minikube/install.sh b/src/kubectl-helm-minikube/install.sh
index f0cf1c946..cbafb18e9 100755
--- a/src/kubectl-helm-minikube/install.sh
+++ b/src/kubectl-helm-minikube/install.sh
@@ -28,22 +28,12 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 USERHOME="/home/$USERNAME"
 if [ "$USERNAME" = "root" ]; then
diff --git a/src/node/install.sh b/src/node/install.sh
index 71d91ffe2..e241d47d7 100755
--- a/src/node/install.sh
+++ b/src/node/install.sh
@@ -247,22 +247,12 @@ if ! type awk >/dev/null 2>&1; then
     check_packages awk
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 # Ensure apt is in non-interactive to avoid prompts
 export DEBIAN_FRONTEND=noninteractive
diff --git a/src/oryx/install.sh b/src/oryx/install.sh
index cf67db6b1..b43580b23 100755
--- a/src/oryx/install.sh
+++ b/src/oryx/install.sh
@@ -25,22 +25,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 function updaterc() {
     if [ "${UPDATE_RC}" = "true" ]; then
diff --git a/src/php/install.sh b/src/php/install.sh
index 357395e88..4eea3a4ed 100755
--- a/src/php/install.sh
+++ b/src/php/install.sh
@@ -36,24 +36,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
-# If in automatic mode, determine if a user already exists, if not use vscode
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ]; then
-    USERNAME=root
-    USER_UID=0
-    USER_GID=0
-fi
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
+# If in automatic mode, determine if a user already exists, if not use root
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 architecture="$(uname -m)"
 if [ "${architecture}" != "amd64" ] && [ "${architecture}" != "x86_64" ] && [ "${architecture}" != "arm64" ] && [ "${architecture}" != "aarch64" ]; then
diff --git a/src/python/install.sh b/src/python/install.sh
index be895927d..86345bd34 100755
--- a/src/python/install.sh
+++ b/src/python/install.sh
@@ -835,22 +835,12 @@ if ! type awk >/dev/null 2>&1; then
     check_packages awk
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 # Ensure apt is in non-interactive to avoid prompts
 export DEBIAN_FRONTEND=noninteractive
diff --git a/src/ruby/install.sh b/src/ruby/install.sh
index 39cb5be03..87a6d7384 100755
--- a/src/ruby/install.sh
+++ b/src/ruby/install.sh
@@ -39,22 +39,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 updaterc() {
     if [ "${UPDATE_RC}" = "true" ]; then
diff --git a/src/rust/install.sh b/src/rust/install.sh
index 99a7ba8f5..54bcd1748 100755
--- a/src/rust/install.sh
+++ b/src/rust/install.sh
@@ -101,22 +101,12 @@ rm -f /etc/profile.d/00-restore-env.sh
 echo "export PATH=${PATH//$(sh -lc 'echo $PATH')/\$PATH}" > /etc/profile.d/00-restore-env.sh
 chmod +x /etc/profile.d/00-restore-env.sh
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u "${CURRENT_USER}" > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u "${USERNAME}" > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 # Figure out correct version of a three part version number is not passed
 find_version_from_git_tags() {
diff --git a/src/sshd/install.sh b/src/sshd/install.sh
index 9b9ddedf2..281d095b4 100755
--- a/src/sshd/install.sh
+++ b/src/sshd/install.sh
@@ -25,22 +25,12 @@ if [ "$(id -u)" -ne 0 ]; then
     exit 1
 fi
 
+# Source common helper functions
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../_common/common-setup.sh"
+
 # Determine the appropriate non-root user
-if [ "${USERNAME}" = "auto" ] || [ "${USERNAME}" = "automatic" ]; then
-    USERNAME=""
-    POSSIBLE_USERS=("vscode" "node" "codespace" "$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd)")
-    for CURRENT_USER in "${POSSIBLE_USERS[@]}"; do
-        if id -u ${CURRENT_USER} > /dev/null 2>&1; then
-            USERNAME=${CURRENT_USER}
-            break
-        fi
-    done
-    if [ "${USERNAME}" = "" ]; then
-        USERNAME=root
-    fi
-elif [ "${USERNAME}" = "none" ] || ! id -u ${USERNAME} > /dev/null 2>&1; then
-    USERNAME=root
-fi
+USERNAME=$(determine_user_from_input "${USERNAME}" "root")
 
 apt_get_update()
 {
diff --git a/test/_common/test-common-setup.sh b/test/_common/test-common-setup.sh
new file mode 100755
index 000000000..149571e50
--- /dev/null
+++ b/test/_common/test-common-setup.sh
@@ -0,0 +1,221 @@
+#!/bin/bash
+#-------------------------------------------------------------------------------------------------------------------------
+# Tests for common-setup.sh helper functions
+# These tests validate the determine_user_from_input function
+#-------------------------------------------------------------------------------------------------------------------------
+
+set -e
+
+# Source the helper script
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "${SCRIPT_DIR}/../../src/_common/common-setup.sh"
+
+# Test counters
+PASSED=0
+FAILED=0
+TOTAL=0
+
+# Helper function to run a test
+run_test() {
+    local test_name="$1"
+    local expected="$2"
+    local actual="$3"
+    
+    TOTAL=$((TOTAL + 1))
+    
+    if [ "${expected}" = "${actual}" ]; then
+        echo "✓ PASS: ${test_name}"
+        PASSED=$((PASSED + 1))
+    else
+        echo "✗ FAIL: ${test_name}"
+        echo "  Expected: '${expected}'"
+        echo "  Actual:   '${actual}'"
+        FAILED=$((FAILED + 1))
+    fi
+}
+
+# Test 1: Automatic mode finds existing user or fallback
+test_automatic_no_users() {
+    local result=$(determine_user_from_input "automatic")
+    # Should find either a known user or fallback to root
+    # On this system, there may be a UID 1000 user (like packer)
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-root}"
+    run_test "Automatic mode with no matching common users finds UID 1000 or root" "${expected}" "${result}"
+}
+
+# Test 2: Automatic mode with fallback user
+test_automatic_with_fallback() {
+    local result=$(determine_user_from_input "automatic" "vscode")
+    # Should find a user or use the fallback - check if UID 1000 exists
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-vscode}"
+    run_test "Automatic mode with custom fallback finds UID 1000 or uses fallback" "${expected}" "${result}"
+}
+
+# Test 3: Explicit "none" should return root
+test_none_returns_root() {
+    local result=$(determine_user_from_input "none")
+    run_test "Explicit 'none' returns root" "root" "${result}"
+}
+
+# Test 4: Explicit "none" ignores fallback
+test_none_ignores_fallback() {
+    local result=$(determine_user_from_input "none" "vscode")
+    run_test "Explicit 'none' ignores fallback" "root" "${result}"
+}
+
+# Test 5: Existing user (root) should return root
+test_existing_user_root() {
+    local result=$(determine_user_from_input "root")
+    run_test "Existing user 'root' returns root" "root" "${result}"
+}
+
+# Test 6: Non-existing user should return root
+test_nonexisting_user() {
+    local result=$(determine_user_from_input "nonexistentuser12345")
+    run_test "Non-existing user returns root" "root" "${result}"
+}
+
+# Test 7: Auto mode (synonym for automatic)
+test_auto_synonym() {
+    local result=$(determine_user_from_input "auto" "customfallback")
+    # Should behave same as automatic - find UID 1000 or use fallback
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-customfallback}"
+    run_test "Auto mode with fallback finds UID 1000 or uses fallback" "${expected}" "${result}"
+}
+
+# Test 8: _REMOTE_USER environment variable (when set and not root)
+test_remote_user_set() {
+    # Test with an existing user (root is always available)
+    # We'll use a user that exists on the system
+    local existing_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo 'root')
+    
+    export _REMOTE_USER="${existing_user}"
+    local result=$(determine_user_from_input "automatic")
+    unset _REMOTE_USER
+    
+    run_test "_REMOTE_USER set to non-root user" "${existing_user}" "${result}"
+}
+
+# Test 9: _REMOTE_USER set to root should use fallback logic
+test_remote_user_root() {
+    export _REMOTE_USER="root"
+    local result=$(determine_user_from_input "automatic" "mydefault")
+    unset _REMOTE_USER
+    
+    # Should use fallback logic - find UID 1000 or use fallback
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-mydefault}"
+    run_test "_REMOTE_USER set to root uses fallback logic" "${expected}" "${result}"
+}
+
+# Test 10: Finding vscode user if it exists
+test_find_vscode_user() {
+    # Check if vscode user exists and no higher priority users exist
+    if id -u vscode > /dev/null 2>&1 && \
+       ! id -u devcontainer > /dev/null 2>&1; then
+        # Unset _REMOTE_USER to ensure it doesn't interfere
+        unset _REMOTE_USER
+        local result=$(determine_user_from_input "automatic")
+        # Should find vscode (it's second in priority after devcontainer)
+        run_test "Finds vscode user in automatic mode" "vscode" "${result}"
+    else
+        # Skip this test if vscode user doesn't exist or higher priority user exists
+        run_test "Finds vscode user in automatic mode (SKIPPED - conditions not met)" "SKIP" "SKIP"
+    fi
+}
+
+# Test 11: Finding devcontainer user (highest priority)
+test_find_devcontainer_user() {
+    # Check if devcontainer user exists
+    if id -u devcontainer > /dev/null 2>&1; then
+        # Unset _REMOTE_USER to ensure it doesn't interfere
+        unset _REMOTE_USER
+        local result=$(determine_user_from_input "automatic")
+        # Should find devcontainer (highest priority)
+        run_test "Finds devcontainer user (highest priority)" "devcontainer" "${result}"
+    else
+        # Skip this test if devcontainer user doesn't exist
+        run_test "Finds devcontainer user (highest priority) (SKIPPED - user doesn't exist)" "SKIP" "SKIP"
+    fi
+}
+
+# Test 12: Finding user with UID 1000
+test_find_uid_1000() {
+    # Check if there's a user with UID 1000
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    
+    if [ -n "${uid_1000_user}" ] && \
+       ! id -u devcontainer > /dev/null 2>&1 && \
+       ! id -u vscode > /dev/null 2>&1 && \
+       ! id -u node > /dev/null 2>&1 && \
+       ! id -u codespace > /dev/null 2>&1; then
+        # Only test if UID 1000 exists and no higher priority users exist
+        local result=$(determine_user_from_input "automatic")
+        run_test "Finds user with UID 1000" "${uid_1000_user}" "${result}"
+    else
+        # Skip this test if conditions aren't met
+        run_test "Finds user with UID 1000 (SKIPPED - conditions not met)" "SKIP" "SKIP"
+    fi
+}
+
+# Test 13: Empty input defaults to "automatic"
+test_empty_input() {
+    local result=$(determine_user_from_input "" "mydefault")
+    # Should behave as automatic mode - find UID 1000 or use fallback
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-mydefault}"
+    run_test "Empty input treated as automatic and finds UID 1000 or uses fallback" "${expected}" "${result}"
+}
+
+# Test 14: _REMOTE_USER set to non-existent user should use fallback
+test_remote_user_nonexistent() {
+    export _REMOTE_USER="nonexistentuser99999"
+    local result=$(determine_user_from_input "automatic" "mydefault")
+    unset _REMOTE_USER
+    
+    # Should fall through to normal detection - find UID 1000 or use fallback
+    local uid_1000_user=$(awk -v val=1000 -F ":" '$3==val{print $1}' /etc/passwd 2>/dev/null || echo '')
+    local expected="${uid_1000_user:-mydefault}"
+    run_test "_REMOTE_USER set to non-existent user falls back to detection" "${expected}" "${result}"
+}
+
+# Run all tests
+echo "Running tests for common-setup.sh..."
+echo "======================================"
+echo ""
+
+test_automatic_no_users
+test_automatic_with_fallback
+test_none_returns_root
+test_none_ignores_fallback
+test_existing_user_root
+test_nonexisting_user
+test_auto_synonym
+test_remote_user_set
+test_remote_user_root
+test_find_vscode_user
+test_find_devcontainer_user
+test_find_uid_1000
+test_empty_input
+test_remote_user_nonexistent
+
+# Print summary
+echo ""
+echo "======================================"
+echo "Test Summary:"
+echo "  Total:  ${TOTAL}"
+echo "  Passed: ${PASSED}"
+echo "  Failed: ${FAILED}"
+echo "======================================"
+
+# Exit with appropriate code
+if [ ${FAILED} -eq 0 ]; then
+    echo "All tests passed! ✓"
+    exit 0
+else
+    echo "Some tests failed! ✗"
+    exit 1
+fi