Add Dockerfile and backup script for SSH server setup

Dockerfile

@@ -0,0 +1,11 @@
+FROM alpine:latest
+
+RUN apk add --no-cache \
+    openssh-server-pam \
+    su-exec \
+    borgbackup
+
+COPY start_backup.sh /start_backup.sh
+RUN chmod +x /start_backup.sh
+
+CMD /start_backup.sh

start_backup.sh

@@ -0,0 +1,65 @@
+#!/bin/sh
+
+SSH_PORT=${SSH_PORT:-20022}
+SSH_USER=${SSH_USER:-"backup"}
+SSH_PASSWORD=${SSH_PASSWORD:-"backup"}
+HOME="/home/$SSH_USER"
+SSH_DIR="$HOME/.ssh"
+SSH_CONFIG_DIR="$HOME/.ssh/server"
+SSH_HOST_KEYS_DIR="$SSH_CONFIG_DIR/keys"
+SSH_CONFIG_FILE="$SSH_CONFIG_DIR/sshd_config"
+SSH_PID_FILE="$SSH_CONFIG_DIR/sshd.pid"
+
+if ! id -u "$SSH_USER" >/dev/null 2>&1; then
+    echo "Creating user $SSH_USER..."
+    adduser -D -s /bin/sh -h "/home/$SSH_USER" "$SSH_USER"
+    # Ensure the user is properly initialized in shadow database
+    passwd -u "$SSH_USER" 2>/dev/null || true
+fi
+
+# Create necessary directories
+mkdir -p "$SSH_CONFIG_DIR" "$SSH_HOST_KEYS_DIR"
+
+# Generate host keys if they don't exist
+for key_type in rsa ed25519; do
+    key_file="$SSH_HOST_KEYS_DIR/ssh_host_${key_type}_key"
+    echo "Generating $key_type host key..."
+    ssh-keygen -t "$key_type" -f "$key_file" -N "" -q
+done
+
+# Add default ssh password if not set
+echo "$SSH_USER:$SSH_PASSWORD" | chpasswd
+
+cat >"$SSH_CONFIG_FILE" <<EOF
+Port $SSH_PORT
+ListenAddress 0.0.0.0
+HostKey $SSH_HOST_KEYS_DIR/ssh_host_rsa_key
+HostKey $SSH_HOST_KEYS_DIR/ssh_host_ed25519_key
+PidFile $SSH_PID_FILE
+UsePam yes
+AuthorizedKeysFile $SSH_DIR/authorized_keys
+PasswordAuthentication yes
+PubkeyAuthentication yes
+ChallengeResponseAuthentication no
+PrintMotd no
+AcceptEnv LANG LC_*
+Subsystem sftp /usr/lib/openssh/sftp-server
+EOF
+
+chown -R $SSH_USER:$SSH_USER "/home/$SSH_USER"
+# Start SSH daemon
+echo "Starting SSH server on port $SSH_PORT..."
+exec su-exec $SSH_USER /usr/sbin/sshd.pam -D -f "$SSH_CONFIG_FILE" -e &
+
+SSH_CONFIG_FILE=$SSH_CONFIG_FILE
+LAST=$(md5sum "$SSH_CONFIG_FILE")
+while true; do
+    sleep 0.1
+    if [ -f "$SSH_CONFIG_FILE" ]; then
+        NEW=$(md5sum "$SSH_CONFIG_FILE")
+        if [ "$NEW" != "$LAST" ]; then
+            pkill -HUP sshd.pam
+            LAST="$NEW"
+        fi
+    fi
+done