diff --git a/.dockerignore b/.dockerignore
new file mode 100644
index 0000000..6c7b69a
--- /dev/null
+++ b/.dockerignore
@@ -0,0 +1 @@
+.gitignore
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 152185a..983cb6c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,11 +17,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+
       - run: sudo apt-get update && sudo apt-get install -y --no-install-recommends binfmt-support qemu-user-static
+
       - run: ./build.sh
-      - run: ./test.sh shellsu-amd64
-      - run: ./test.sh shellsu-i386
-      - run: ./test.sh --debian shellsu-amd64
-      - run: ./test.sh --debian shellsu-i386
+      - run: ./test.sh --alpine shellsu
+      - run: ./test.sh --debian shellsu
       - run: docker build --pull --file hub/Dockerfile.alpine hub
       - run: docker build --pull --file hub/Dockerfile.debian hub
diff --git a/Dockerfile b/Dockerfile
index a2c9d27..e8ce417 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,50 +5,25 @@ FROM debian:bookworm-slim
 RUN set -eux; \
     apt-get update; \
     apt-get install -y --no-install-recommends \
-        arch-test \
         file \
         bash \
+        login \
     ; \
     rm -rf /var/lib/apt/lists/*
 
 # Set environment variable for build flags
 ENV BUILD_FLAGS="-v"
 
-# Prepare the `shellsu` build and test script
-RUN set -eux; \
-    { \
-        echo '#!/usr/bin/env bash'; \
-        echo 'set -Eeuo pipefail -x'; \
-        echo 'ARCH="${ARCH:-$(uname -m)}"'; \
-        echo 'cp /usr/local/bin/shellsu /usr/local/bin/shellsu-$ARCH'; \
-        echo 'file "/usr/local/bin/shellsu-$ARCH"'; \
-        echo 'if arch-test "$ARCH"; then'; \
-        echo '  try() { for (( i = 0; i < 30; i++ )); do if timeout 1s "$@"; then return 0; fi; done; return 1; }'; \
-        echo '  try "/usr/local/bin/shellsu-$ARCH" --version'; \
-        echo '  try "/usr/local/bin/shellsu-$ARCH" nobody id'; \
-        echo '  try "/usr/local/bin/shellsu-$ARCH" nobody ls -l /proc/self/fd'; \
-        echo 'fi'; \
-    } > /usr/local/bin/shellsu-build-and-test.sh; \
-    chmod +x /usr/local/bin/shellsu-build-and-test.sh
-
-# Disable CGO (not relevant for Bash, but keeping for alignment with original pattern)
-ENV CGO_ENABLED 0
-
 # Copy `shellsu` script into the container
 WORKDIR /usr/local/bin
-COPY shellsu /usr/local/bin/shellsu
+COPY shellsu.sh /usr/local/bin/shellsu
 RUN chmod +x /usr/local/bin/shellsu
 
-# Test `shellsu` for various architectures
-RUN ARCH=amd64    shellsu-build-and-test.sh
-RUN ARCH=i386     shellsu-build-and-test.sh
-RUN ARCH=armel    shellsu-build-and-test.sh
-RUN ARCH=armhf    shellsu-build-and-test.sh
-RUN ARCH=arm64    shellsu-build-and-test.sh
-RUN ARCH=mips64el shellsu-build-and-test.sh
-RUN ARCH=ppc64el  shellsu-build-and-test.sh
-RUN ARCH=riscv64  shellsu-build-and-test.sh
-RUN ARCH=s390x    shellsu-build-and-test.sh
+# Test `shellsu` to verify functionality
+RUN set -eux; \
+    # Run the script with basic tests
+    ./shellsu --help; \
+    ./shellsu --version
 
-# Final verification step
-RUN set -eux; ls -lAFh /usr/local/bin/shellsu-*; file /usr/local/bin/shellsu-*
+# Final verification step (list files and check permissions)
+RUN set -eux; ls -lAFh /usr/local/bin/shellsu; file /usr/local/bin/shellsu
diff --git a/Dockerfile.test-alpine b/Dockerfile.test-alpine
index e16c359..3563bf6 100644
--- a/Dockerfile.test-alpine
+++ b/Dockerfile.test-alpine
@@ -1,40 +1,49 @@
 FROM alpine:3.20
 
+RUN apk add --no-cache bash coreutils shadow
+
 # Add "nobody" to ALL groups to create edge cases for testing
 RUN cut -d: -f1 /etc/group | xargs -rtn1 addgroup nobody
 
 # Create the `shellsu-t` testing script
 RUN { \
-		echo '#!/bin/sh'; \
-		echo 'set -ex'; \
-		echo; \
-		echo 'spec="$1"; shift'; \
-		echo; \
-		echo 'expec="$1"; shift'; \
-		echo 'real="$(shellsu "$spec" id -u):$(shellsu "$spec" id -g):$(shellsu "$spec" id -G)"'; \
-		echo '[ "$expec" = "$real" ]'; \
-		echo; \
-		echo 'expec="$1"; shift'; \
-		echo 'real="$(shellsu "$spec" id -un):$(shellsu "$spec" id -gn):$(shellsu "$spec" id -Gn)" || true'; \
-		echo '[ "$expec" = "$real" ]'; \
-	} > /usr/local/bin/shellsu-t \
-	&& chmod +x /usr/local/bin/shellsu-t
+    echo '#!/bin/sh'; \
+    echo 'set -ex'; \
+    echo; \
+    echo 'spec="$1"; shift'; \
+    echo; \
+    echo 'expec="$1"; shift'; \
+    echo 'real="$(/usr/local/bin/shellsu "$spec" id -u):$(/usr/local/bin/shellsu "$spec" id -g):$(/usr/local/bin/shellsu "$spec" id -G)"'; \
+    echo '[ "$expec" = "$real" ] || { echo "Test failed"; exit 1; }'; \
+    echo; \
+    echo 'expec="$1"; shift'; \
+    echo 'real="$(/usr/local/bin/shellsu "$spec" id -un):$(/usr/local/bin/shellsu "$spec" id -gn):$(/usr/local/bin/shellsu "$spec" id -Gn)" || true'; \
+    echo '[ "$expec" = "$real" ] || { echo "Test failed"; exit 1; }'; \
+} > /usr/local/bin/shellsu-t \
+&& chmod +x /usr/local/bin/shellsu-t
 
 # Copy the `shellsu` binary/script into the image
-COPY shellsu /usr/local/bin/
+RUN ls -la
+RUN pwd
+COPY shellsu /usr/local/bin/shellsu
 RUN chmod +x /usr/local/bin/shellsu
+RUN ls -la /usr/local/bin/
+RUN echo $PATH
+RUN ls -l $(which su)
 
 # Adjust permissions for testing unusual cases
 RUN chgrp nobody /usr/local/bin/shellsu \
 	&& chmod +s /usr/local/bin/shellsu
 
 # Configure an environment for testing
-ENV SHELLSU_INSECURE_MODE="I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die."
+ENV SHELLSU_INSECURE_FLAG="I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die."
 USER nobody
 ENV HOME /omg/really/shellsu/nowhere
 
 # Validate initial state
 RUN id
+RUN cat /etc/passwd
+RUN cat /etc/group
 
 # Test various user/group configurations
 RUN shellsu-t 0 "0:0:$(id -G root)" "root:root:$(id -Gn root)"
diff --git a/Dockerfile.test-debian b/Dockerfile.test-debian
index bd82225..304055c 100644
--- a/Dockerfile.test-debian
+++ b/Dockerfile.test-debian
@@ -1,5 +1,16 @@
 FROM debian:bookworm-slim
 
+# Install necessary dependencies
+RUN set -eux; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        file \
+        bash \
+        login \
+    ; \
+    rm -rf /var/lib/apt/lists/*
+
+
 # Add "nobody" to ALL groups to create edge cases for testing
 RUN cut -d: -f1 /etc/group | xargs -rtI'{}' usermod -aG '{}' nobody
 # Emulate Alpine's "games" user, which is part of the "users" group
@@ -13,30 +24,38 @@ RUN { \
 		echo 'spec="$1"; shift'; \
 		echo; \
 		echo 'expec="$1"; shift'; \
-		echo 'real="$(shellsu "$spec" id -u):$(shellsu "$spec" id -g):$(shellsu "$spec" id -G)"'; \
+		echo 'real="$(/usr/local/bin/shellsu "$spec" id -u):$(/usr/local/bin/shellsu "$spec" id -g):$(/usr/local/bin/shellsu "$spec" id -G)"'; \
 		echo '[ "$expec" = "$real" ]'; \
 		echo; \
 		echo 'expec="$1"; shift'; \
-		echo 'real="$(shellsu "$spec" id -un):$(shellsu "$spec" id -gn):$(shellsu "$spec" id -Gn)" || true'; \
+		echo 'real="$(/usr/local/bin/shellsu "$spec" id -un):$(/usr/local/bin/shellsu "$spec" id -gn):$(/usr/local/bin/shellsu "$spec" id -Gn)" || true'; \
 		echo '[ "$expec" = "$real" ]'; \
 	} > /usr/local/bin/shellsu-t \
 	&& chmod +x /usr/local/bin/shellsu-t
 
 # Copy the `shellsu` binary/script into the image
-COPY shellsu /usr/local/bin/
+RUN ls -la
+RUN pwd
+COPY shellsu /usr/local/bin/shellsu
+COPY shellsu /usr/local/bin/shellsu
 RUN chmod +x /usr/local/bin/shellsu
+RUN ls -la /usr/local/bin/
+RUN echo $PATH
+RUN ls -l $(which su)
 
 # Adjust permissions for testing unusual cases
 RUN chgrp nogroup /usr/local/bin/shellsu \
 	&& chmod +s /usr/local/bin/shellsu
 
 # Configure an environment for testing
-ENV SHELLSU_INSECURE_MODE="I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die."
+ENV SHELLSU_INSECURE_FLAG="I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die."
 USER nobody
 ENV HOME /omg/really/shellsu/nowhere
 
 # Validate initial state
 RUN id
+RUN cat /etc/passwd
+RUN cat /etc/group
 
 # Test various user/group configurations
 RUN shellsu-t 0 "0:0:$(id -G root)" "root:root:$(id -Gn root)"
diff --git a/build.sh b/build.sh
index 00b169c..519f3c9 100755
--- a/build.sh
+++ b/build.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -e
 
 # Navigate to the directory containing this script
@@ -7,20 +7,17 @@ cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
 set -x
 
 # Build the Docker image
-docker build --pull -t shellsu .
+docker build --no-cache --pull -t shellsu .
 
-# Clean up any pre-existing artifacts
 rm -f shellsu* SHA256SUMS*
 
-# Extract the `shellsu` binaries from the built image
-docker run --rm shellsu sh -c 'cd /go/bin && tar -c shellsu*' | tar -xv
+docker run --rm --entrypoint cat shellsu /usr/local/bin/shellsu > shellsu
 
-# Generate SHA256 checksums for the extracted files
-sha256sum shellsu* | tee SHA256SUMS
+chmod +x shellsu
 
-# Inspect the extracted files
-file shellsu*
-ls -lFh shellsu* SHA256SUMS*
+sha256sum shellsu | tee SHA256SUMS
 
-# Run the built binary to verify functionality
-"./shellsu-$(dpkg --print-architecture)" --help
+file shellsu
+ls -lFh shellsu SHA256SUMS
+
+"./shellsu" --help
diff --git a/hub/Dockerfile.alpine b/hub/Dockerfile.alpine
index 652bad6..f279608 100644
--- a/hub/Dockerfile.alpine
+++ b/hub/Dockerfile.alpine
@@ -1,6 +1,6 @@
 FROM alpine:3.20
 
-# https://github.com/tianon/shellsu/releases
+# https://github.com/dogruis/shellsu/releases
 ENV SHELLSU_VERSION 1.17
 
 RUN set -eux; \
diff --git a/hub/Dockerfile.debian b/hub/Dockerfile.debian
index 891ed8f..fec06aa 100644
--- a/hub/Dockerfile.debian
+++ b/hub/Dockerfile.debian
@@ -1,6 +1,6 @@
 FROM debian:bookworm-slim
 
-# https://github.com/tianon/shellsu/releases
+# https://github.com/dogruis/shellsu/releases
 ENV SHELLSU_VERSION 1.17
 
 RUN set -eux; \
diff --git a/shellsu.sh b/shellsu.sh
index f28c60f..f1dccfd 100755
--- a/shellsu.sh
+++ b/shellsu.sh
@@ -4,16 +4,20 @@ set -Eeuo pipefail
 # Script Metadata
 VERSION="1.0"
 SCRIPT_NAME="$(basename "$0")"
-LICENSE_TEXT="Apache-2.0 (see https://github.com/tianon/gosu)"
+LICENSE_TEXT="MIT (see https://github.com/dogruis/shellsu)"
 
 # Helper Functions
 usage() {
     cat <<EOF
 Usage: $SCRIPT_NAME user-spec command [args...]
-   eg: $SCRIPT_NAME tianon bash
+   eg: $SCRIPT_NAME dogruis bash
        $SCRIPT_NAME nobody:root bash -c 'whoami && id'
        $SCRIPT_NAME 1000:1 id
 
+Options:
+  --help, -h           Show this help message
+  --version, -v        Show version information
+
 $SCRIPT_NAME version: $VERSION
 $SCRIPT_NAME license: $LICENSE_TEXT
 EOF
@@ -29,61 +33,110 @@ error_exit() {
     exit 1
 }
 
-# Parse and validate user:group spec
-parse_user_spec() {
-    local spec="$1"
-    USER="${spec%%:*}"
-    GROUP="${spec#*:}"
-    [[ "$USER" == "$GROUP" ]] && GROUP=""
-
-    id "$USER" &>/dev/null || error_exit "User '$USER' does not exist."
-    if [[ -n "$GROUP" ]]; then
-        getent group "$GROUP" &>/dev/null || error_exit "Group '$GROUP' does not exist."
+# Check if the script is insecure (no setuid/setgid bit)
+check_insecure() {
+    if [[ "${SHELLSU_INSECURE_FLAG:-}" != "I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain. Time to die." ]]; then
+        # Check if the script has setuid or setgid permissions
+        if [[ -u "$0" ]]; then
+            error_exit "$0 appears to be installed with the 'setuid' bit set, which is extremely insecure and unsupported! Use 'sudo' or 'su' instead."
+        elif [[ -g "$0" ]]; then
+            error_exit "$0 appears to be installed with the 'setgid' bit set, which is not great and unsupported! Use 'sudo' or 'su' instead."
+        fi
     fi
 }
 
-# Switch user and group, then execute the command
-execute_as_user() {
-    local user="$1"
-    local group="$2"
-    shift 2
-    local cmd=("$@")
+# Function to set up the user and group context
+setup_user() {
+    local user_spec="$1"
+    local user_name
+    local user_uid
+    local user_gid
+    local user_home
+    local group_ids=()
 
-    # Resolve group ID if specified
-    if [[ -n "$group" ]]; then
-        GROUP_ID=$(getent group "$group" | cut -d: -f3)
-        sg "$group" <<EOF
-exec su -s /bin/bash -c "$(printf '%q ' "${cmd[@]}")" "$user"
-EOF
+    # Parse user_spec (format: user[:group])
+    IFS=':' read -r user group <<< "$user_spec"
+
+    # Resolve user info from /etc/passwd
+    if [[ "$user" =~ ^[0-9]+$ ]]; then
+        # If user is numeric UID, resolve it
+        user_entry=$(getent passwd | awk -F: -v uid="$user" '$3 == uid {print}')
     else
-        exec su -s /bin/bash -c "$(printf '%q ' "${cmd[@]}")" "$user"
+        # If user is a name, fetch entry
+        user_entry=$(getent passwd "$user")
+    fi
+
+    if [[ -z "$user_entry" ]]; then
+        error_exit "User '$user' not found"
+    fi
+
+    user_name=$(echo "$user_entry" | cut -d: -f1)
+    user_uid=$(echo "$user_entry" | cut -d: -f3)
+    user_gid=$(echo "$user_entry" | cut -d: -f4)
+    user_home=$(echo "$user_entry" | cut -d: -f6)
+
+    # Resolve group info if a specific group is provided
+    if [[ -n "$group" ]]; then
+        if [[ "$group" =~ ^[0-9]+$ ]]; then
+            group_entry=$(getent group | awk -F: -v gid="$group" '$3 == gid {print}')
+        else
+            group_entry=$(getent group "$group")
+        fi
+        if [[ -z "$group_entry" ]]; then
+            error_exit "Group '$group' not found"
+        fi
+        user_gid=$(echo "$group_entry" | cut -d: -f3)
+    fi
+
+    # Resolve supplementary groups
+    group_ids=($(id -G "$user_name"))
+
+    # Set user and group IDs
+    if ! setpriv --reuid="$user_uid" --regid="$user_gid" --init-groups true; then
+        error_exit "Failed to switch to user '$user_name' and group '$group'"
     fi
+
+    # Set HOME environment variable
+    export HOME="$user_home"
+}
+
+# Function to switch to user and group and execute command
+run_cmd_as_user() {
+    spec="$1"
+    shift
+    cmd=("$@")
+
+    # Setup the user environment
+    setup_user "$spec"
+
+    # Execute the command as the specified user and group
+    exec "${cmd[@]}"
 }
 
-# Main Script Logic
+# Main function to execute the script logic
 main() {
-    if [[ "$#" -lt 2 ]]; then
+    check_insecure
+
+    # Handle the command-line arguments
+    if [[ $# -ge 2 ]]; then
+        case "$1" in
+            "--help" | "-h" | "-?")
+                usage
+                exit 0
+                ;;
+            "--version" | "-v")
+                version
+                exit 0
+                ;;
+        esac
+    else
         usage
         exit 1
     fi
 
-    case "$1" in
-        --help | -h)
-            usage
-            exit 0
-            ;;
-        --version | -v)
-            version
-            exit 0
-            ;;
-    esac
-
-    USER_SPEC="$1"
-    shift
-    COMMAND=("$@")
-
-    parse_user_spec "$USER_SPEC"
-    execute_as_user "$USER" "$GROUP" "${COMMAND[@]}"
+    # Call the user switching and command execution function
+    run_cmd_as_user "$@"
 }
 
+# Call the main function
 main "$@"
diff --git a/test.sh b/test.sh
index d63f4b9..43454b0 100755
--- a/test.sh
+++ b/test.sh
@@ -2,9 +2,9 @@
 set -Eeuo pipefail
 
 usage() {
-    echo "usage: $0 [--platform] shellsu-binary"
-    echo "   eg: $0 ./shellsu-amd64"
-    echo "       $0 --debian ./shellsu-amd64"
+    echo "usage: $0 [--alpine | --debian] shellsu"
+    echo "   eg: $0 --debian ./shellsu"
+    echo "       $0 --alpine ./shellsu"
 }
 
 df='Dockerfile.test-alpine'
@@ -16,28 +16,45 @@ case "${1:-}" in
 esac
 
 shellsu="${1:-}"
-shift || { usage >&2; exit 1; }
-[ -f "$shellsu" ] || { usage >&2; exit 1; }
+shift || { echo "Error: Missing shellsu script argument." >&2; usage >&2; exit 1; }
+[ -f "$shellsu" ] || { echo "Error: shellsu script '$shellsu' does not exist." >&2; usage >&2; exit 1; }
 
-trap '{ set +x; echo; echo FAILED; echo; } >&2' ERR
-
-set -x
+echo "Verifying Dockerfile: $df"
+[ -f "$df" ] || { echo "Error: Dockerfile '$df' does not exist." >&2; exit 1; }
 
 dir="$(mktemp -d -t shellsu-test-XXXXXXXXXX)"
 base="$(basename "$dir")"
 img="shellsu-test:$base"
 trap "rm -rf '$dir'" EXIT
-cp -T "$df" "$dir/Dockerfile"
-cp -T "$shellsu" "$dir/shellsu"
-docker build -t "$img" "$dir"
-rm -rf "$dir"
+
+echo "Using temporary directory: $dir"
+echo "Docker image will be tagged as: $img"
+echo "Copying shellsu script '$shellsu' to $dir/shellsu"
+echo "Copying Dockerfile '$df' to $dir/Dockerfile"
+
+cp -T "$df" "$dir/Dockerfile" || { echo "Error: Failed to copy Dockerfile to '$dir/Dockerfile'." >&2; exit 1; }
+cp -T "$shellsu" "$dir/shellsu" || { echo "Error: Failed to copy '$shellsu' to '$dir/shellsu'." >&2; exit 1; }
+
+echo "Building Docker image '$img' using Dockerfile '$df'..."
+docker build -t "$img" "$dir" || { echo "Error: Failed to build Docker image '$img'." >&2; exit 1; }
+rm -rf "$dir"  # Clean up the temporary directory
 trap - EXIT
 
 trap "docker rm -f '$base' > /dev/null; docker rmi -f '$img' > /dev/null" EXIT
 
-# using explicit "--init=false" in case dockerd is running with "--init" (because that will skew our process numbers)
-docker run -d --init=false --name "$base" "$img" shellsu root sleep 1000
-sleep 1 # give it plenty of time to get through "shellsu" and into the "sleep"
-[ "$(docker top "$base" | wc -l)" = 2 ]
-# "docker top" should have only two lines
-# -- ps headers and a single line for the single process running in the container
+echo "Testing shellsu script with --help and --version..."
+docker run --rm "$img" /usr/local/bin/shellsu --help || { echo "Error: Failed to run '/usr/local/bin/shellsu --help' inside the container." >&2; exit 1; }
+docker run --rm "$img" /usr/local/bin/shellsu --version || { echo "Error: Failed to run '/usr/local/bin/shellsu --version' inside the container." >&2; exit 1; }
+
+echo "Running the shellsu script with sleep for basic functionality check..."
+docker run -d --init=false --name "$base" "$img" /usr/local/bin/shellsu root sleep 1000 || { echo "Error: Failed to start container with '/usr/local/bin/shellsu root sleep 1000'." >&2; exit 1; }
+
+sleep 1  # Allow some time for the script to run
+echo "Checking process count..."
+process_count=$(docker top "$base" | wc -l)
+if [ "$process_count" -ne 2 ]; then
+    echo "Error: Unexpected number of processes in container (expected 2, found $process_count)." >&2
+    exit 1
+fi
+
+echo "Test passed successfully!"