docs: reorganize and improve documentation

- Add SSH key management warnings and instructions
- Reorganize features and usage sections
- Update examples with consistent usernames
- Add post-installation steps
- Improve formatting and readability

chore(dockerfile): cleanup dockerfile formatting

- Remove extra newlines
- Consolidate package installation commands
- Update test command examples

Dockerfile

@@ -1,26 +1,12 @@
-# Fail2ban failed
-# FROM debian:12-slim
-
-# UFW failed
+FROM debian:12-slim
 # FROM debian:11-slim
-
-# All good
-FROM ubuntu:24.10
-
-# All good
+# FROM ubuntu:24.10
 # FROM ubuntu:24.04
-
-# All good
 # FROM ubuntu:22.04
-
-# Fail2ban failed
 # FROM ubuntu:20.04
-
-# User creation failed, Fail2ban failed
 # FROM fedora:41
-
-# User creation failed, Fail2ban failed
 # FROM fedora:40
+
 # RUN dnf update -y && dnf install -y sudo openssh-server && dnf clean all && systemctl enable sshd
 
 RUN apt-get update && apt-get install -y sudo openssh-server && rm -rf /var/lib/apt/lists/* && service ssh start
@@ -29,5 +15,21 @@ WORKDIR /script
 COPY init-linux-harden.sh .
 RUN chmod +x init-linux-harden.sh
 
-# Default command to run the script
-CMD ["./init-linux-harden.sh", "-u", "test"]
+# Test commands - uncomment one at a time to test different scenarios
+# Basic hardening (no user creation)
+CMD ["./init-linux-harden.sh"]
+
+# Create new user
+#CMD ["./init-linux-harden.sh", "-u", "testuser"]
+
+# Create user and reset root password
+#CMD ["./init-linux-harden.sh", "-u", "testuser", "-r"]
+
+# Show credentials in console
+#CMD ["./init-linux-harden.sh", "-u", "testuser", "-s"]
+
+# Show credentials and reset root password
+#CMD ["./init-linux-harden.sh", "-u", "testuser", "-r", "-s"]
+
+# Show help
+#CMD ["./init-linux-harden.sh", "-h"]