diff --git a/README.md b/README.md
index 8dc0a2e..5dc9f84 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,18 @@
+Version 0.4 Changelogs:
+- Replaced auto-generated usernames with user-defined usernames
+- Added username validation (3-32 characters, alphanumeric + underscore only)
+- Implemented duplicate username checking
+- Enhanced error handling for invalid username formats
+- Added user-friendly error messages for username validation
+- Maintained backward compatibility with existing user management
+
+Version 0.3 Changelogs:
+- Fixed SSH configuration handling to prevent duplicate Match User entries
+- Implemented idempotent sshd_config modification using pattern matching and deduplication
+- Added atomic configuration updates with proper indentation handling
+- Removed redundant SSH service restarts while maintaining reliability
+- Added configuration validation before applying changes
+
 Version 0.2 Changelogs:
 - Added a submitUnchanged property to allow submitting the 'Add User' form even if the settings haven't been changed.
 - Changed required: true to required: false for the 'Accept User Creation' checkbox
diff --git a/add-sftp.sh b/add-sftp.sh
index 60860c5..ade4dee 100644
--- a/add-sftp.sh
+++ b/add-sftp.sh
@@ -24,9 +24,14 @@ log_debug() {
     fi
 }
 
-# Generate random username
-generate_username() {
-    echo "user$(shuf -i 10000-99999 -n 1)"
+# Validate username format
+validate_username() {
+    local username=$1
+    if ! [[ $username =~ ^[a-zA-Z0-9_]{3,32}$ ]]; then
+        log_error "Invalid username format. Username must be 3-32 characters long and contain only letters, numbers, and underscores."
+        return 1
+    fi
+    return 0
 }
 
 USERNAME=$1
@@ -35,11 +40,16 @@ SSH_ENABLED=$3
 
 log "Script started"
 
-# Check if user already exists, if yes generate a new one
-while id "$USERNAME" &>/dev/null; do
-    USERNAME=$(generate_username)
-    log_warning "Username $USERNAME already exists, generating a new username."
-done
+# Validate username format
+if ! validate_username "$USERNAME"; then
+    exit 1
+fi
+
+# Check if user already exists
+if id "$USERNAME" &>/dev/null; then
+    log_error "Username $USERNAME already exists. Please choose a different username."
+    exit 1
+fi
 
 USER_HOME="/home/sftpusers/$USERNAME"
 ROOT_DIRECTORY="/var/www/webroot/ROOT"
diff --git a/manifest.jps b/manifest.jps
index cb29495..ab3657e 100644
--- a/manifest.jps
+++ b/manifest.jps
@@ -1,4 +1,4 @@
-version: 0.2
+version: 0.4
 id: addsftp
 type: update
 description: An addon to add new SFTP users. It can also manage created user accounts. If SSH is enabled, WP-CLI will attempt to be installed if it is not yet installed.
@@ -16,6 +16,13 @@ settings:
       caption: Root Directory /var/www/webroot/ROOT/
       description: "A user-specific directory will be created under /home/username"
       required: false  
+    - type: string
+      name: custom_username
+      caption: Custom Username
+      description: "Enter a custom username (3-32 characters, alphanumeric + underscore only)"
+      required: true
+      regex: ^[a-zA-Z0-9_]{3,32}$
+      regexText: "Username must be 3-32 characters long and contain only letters, numbers, and underscores"
     - type: checkbox
       name: allow
       caption: Accept User Creation
@@ -60,7 +67,7 @@ settings:
       
 
 globals:
-  username: "user${fn.random(10000,99999)}"
+  username: ${settings.custom_username}
   password: ${fn.password(min)}
   sftpHost: ${env.domain}
   sftpPort: 22
@@ -75,9 +82,15 @@ onInstall:
         wget https://deploy-proxy.mightybox.io/addons/add-sftp-user/raw/branch/main/add-sftp.sh -O /home/jelastic/add-sftp-user-addon/add-sftp.sh
         chmod +x /home/jelastic/add-sftp-user-addon/*.sh
   - cmd[cp]: 
-      user: root
-      commands: 
-        - echo -e "\nMatch User user*\nPasswordAuthentication yes" >> /etc/ssh/sshd_config
+    user: root
+    commands: |-
+      if grep -qE "^Match User user[0-9]*$" /etc/ssh/sshd_config; then
+          sed -i '/^Match User user[0-9]*/!b;n;c\    PasswordAuthentication yes' /etc/ssh/sshd_config
+      else
+          echo -e "\n# Added by SFTP addon\nMatch User user*\n\tPasswordAuthentication yes" >> /etc/ssh/sshd_config
+      fi
+      awk '!seen[$0]++' /etc/ssh/sshd_config > /etc/ssh/sshd_config.tmp && mv /etc/ssh/sshd_config.tmp /etc/ssh/sshd_config
+      systemctl restart sshd
   - cmd[cp]: 
       user: root
       commands: