diff --git a/README.md b/README.md
index ac83478..61a89ba 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@ A Yunohost package for [Mattermost](http://www.mattermost.org/), an open-source,
 
 Mattermost requires:
 
-* A x86_64 system (check with `uname -m`),
+* A x86_64 system (check with `uname -m`) (ARM Raspberry Pi won’t work, sorry),
 * Yunohost 3.2 or higher (check in Yunohost Admin panel),
 * MySQL 5.6 or higher, or MariaDB 10 or higher (check with `mysql --version`).
 
diff --git a/check_process b/check_process
index b6d972e..29aff32 100644
--- a/check_process
+++ b/check_process
@@ -3,7 +3,7 @@
         domain="ynhtests.local" (DOMAIN)
         path="/path" (PATH)
         admin_email="john@gmail.com"
-        admin_password="MattermostPassword!42"
+        admin_password="admin!42"
         admin_locale="fr"
         team_display_name="Mon équipe"
         is_public=1 (PUBLIC|public=1|private=0)
diff --git a/manifest.json b/manifest.json
index 993bd1a..8238ec7 100644
--- a/manifest.json
+++ b/manifest.json
@@ -64,8 +64,8 @@
                 "name": "admin_password",
                 "type": "password",
                 "ask": {
-                    "en": "Password for the chat admin. Must contain at least 10 characters, one lowercase letter, one uppercase letter, one number, and one symbol (e.g. '~!@#$%^&*()').",
-                    "fr": "Mot de passe pour l’administrateur du chat. Doit contenir au moins 10 caractères, une majuscule, une minuscule, un chiffre, et une ponctuation (ex. '~!@#$%^&*()')."
+                    "en": "Password for the chat admin. At least 8 characters.",
+                    "fr": "Mot de passe pour l’administrateur du chat. Minimum 8 caractères."
                 },
                 "optional": false
             },
diff --git a/scripts/install b/scripts/install
index 226b97c..7972c68 100644
--- a/scripts/install
+++ b/scripts/install
@@ -97,7 +97,7 @@ logs_path="/var/log/$app"
 
 db_name="$app"
 db_user="mmuser"
-db_password=$(dd if=/dev/urandom bs=1 count=200 2> /dev/null | tr -c -d 'A-Za-z0-9' | sed -n 's/\(.\{24\}\).*/\1/p')
+db_password=$(ynh_string_random --length=24)
 ynh_mysql_create_db "$db_name" "$db_user" "$db_password"
 ynh_app_setting_set "$app" mysqlpwd "$db_password"
 
@@ -106,7 +106,7 @@ ynh_app_setting_set "$app" mysqlpwd "$db_password"
 #=================================================
 
 mattermost_user="$app"
-mattermost_user_password=$(dd if=/dev/urandom bs=1 count=200 2> /dev/null | tr -c -d 'A-Za-z0-9' | sed -n 's/\(.\{24\}\).*/\1/p')
+mattermost_user_password=$(ynh_string_random --length=24)
 useradd -M --shell /bin/false -p $(openssl passwd -1 "$mattermost_user_password") "$mattermost_user"
 ynh_app_setting_set "$app" smtppwd "$mattermost_user_password"
 
@@ -125,28 +125,34 @@ mkdir -p "$logs_path"
 #=================================================
 
 # Configure Service Settings
-sed -i "s|\"SiteURL\": \"\"|\"SiteURL\": \"https://${domain}${path_url}\"|g"          $final_path/config/config.json
-sed -i "s|\"ListenAddress\": \".*\"|\"ListenAddress\": \"127.0.0.1:${port}\"|g"       $final_path/config/config.json
+ynh_replace_string --match_string "\"SiteURL\": \"\""                 --replace_string "\"SiteURL\": \"https://${domain}${path_url}\""     --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"ListenAddress\": \".*\""         --replace_string "\"ListenAddress\": \"127.0.0.1:${port}\""          --target_file $final_path/config/config.json
 # Configure the database connection
 db_connection_url="${db_user}:${db_password}@tcp(127.0.0.1:3306)/${db_name}?charset=utf8mb4,utf8"
-sed -i "s|\"DataSource\": \".*\"|\"DataSource\": \"${db_connection_url}\"|g"          $final_path/config/config.json
+ynh_replace_string --match_string "\"DataSource\": \".*\""            --replace_string "\"DataSource\": \"${db_connection_url}\""          --target_file $final_path/config/config.json
 # Configure uploaded files directory
-sed -i "s|\"Directory\": \"./data/\"|\"Directory\": \"${data_path}/\"|g"              $final_path/config/config.json
+ynh_replace_string --match_string "\"Directory\": \"./data/\""        --replace_string "\"Directory\": \"${data_path}/\""                  --target_file $final_path/config/config.json
 # Configure SMTP account for sending email notifications
-sed -i "s|\"SendEmailNotifications\": false|\"SendEmailNotifications\": true|g"       $final_path/config/config.json
-sed -i "s|\"FeedbackName\": \"\"|\"FeedbackName\": \"Mattermost notification\"|g"     $final_path/config/config.json
-sed -i "s|\"FeedbackEmail\": \"\"|\"FeedbackEmail\": \"no-reply@${domain}\"|g"        $final_path/config/config.json
-sed -i "s|\"SMTPUsername\": \"\"|\"SMTPUsername\": \"${mattermost_user}\"|g"          $final_path/config/config.json
-sed -i "s|\"SMTPPassword\": \"\"|\"SMTPPassword\": \"${mattermost_user_password}\"|g" $final_path/config/config.json
-sed -i "s|\"SMTPServer\": \"\"|\"SMTPServer\": \"localhost\"|g"                       $final_path/config/config.json
-sed -i "s|\"SMTPPort\": \"\"|\"SMTPPort\": \"25\"|g"                                  $final_path/config/config.json
+ynh_replace_string --match_string "\"SendEmailNotifications\": false" --replace_string "\"SendEmailNotifications\": true"                  --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"FeedbackName\": \"\""            --replace_string "\"FeedbackName\": \"Mattermost notification\""     --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"FeedbackEmail\": \"\""           --replace_string "\"FeedbackEmail\": \"no-reply@${domain}\""         --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"SMTPUsername\": \"\""            --replace_string "\"SMTPUsername\": \"${mattermost_user}\""          --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"SMTPPassword\": \"\""            --replace_string "\"SMTPPassword\": \"${mattermost_user_password}\"" --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"SMTPServer\": \"\""              --replace_string "\"SMTPServer\": \"localhost\""                     --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"SMTPPort\": \"\""                --replace_string "\"SMTPPort\": \"25\""                              --target_file $final_path/config/config.json
 # Disable Mattermost debug console by default
-sed -i "s|\"EnableConsole\": true|\"EnableConsole\": false|g"                         $final_path/config/config.json
+ynh_replace_string --match_string "\"EnableConsole\": true"           --replace_string "\"EnableConsole\": false"                          --target_file $final_path/config/config.json
 # Configure log file location
-sed -i "s|\"FileLocation\": \"\"|\"FileLocation\": \"$logs_path\"|g"                  $final_path/config/config.json
+ynh_replace_string --match_string "\"FileLocation\": \"\""            --replace_string "\"FileLocation\": \"$logs_path\""                  --target_file $final_path/config/config.json
+# Disable questionable password complexity rules
+ynh_replace_string --match_string "\"MinimumLength\": 10"             --replace_string "\"MinimumLength\": 8"                              --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"Lowercase\": true"               --replace_string "\"Lowercase\": false"                              --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"Number\": true"                  --replace_string "\"Number\": false"                                 --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"Uppercase\": true"               --replace_string "\"Uppercase\": false"                              --target_file $final_path/config/config.json
+ynh_replace_string --match_string "\"Symbol\": true"                  --replace_string "\"Symbol\": false"                                 --target_file $final_path/config/config.json
 # Configure analytics according to user choice
 if [ $analytics -eq 0 ]; then
-    sed -i "s|\"EnableDiagnostics\": true|\"EnableDiagnostics\": false|g"             $final_path/config/config.json
+    ynh_replace_string --match_string "\"EnableDiagnostics\": true"   --replace_string "\"EnableDiagnostics\": false"                      --target_file $final_path/config/config.json
 fi
 ynh_app_setting_set "$app" analytics "$analytics"
 
diff --git a/scripts/upgrade b/scripts/upgrade
index 0e0b1c4..df4af82 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -146,12 +146,12 @@ yunohost service add "$app" --log "$logs_path/mattermost.log"
 
 # Fix log FileLocation path (changed in Mattermost 3.8, makes Mattermost >= 4.2 crash)
 # https://docs.mattermost.com/administration/changelog.html#release-v3-8-3
-sed -i "s|\"FileLocation\": \"/var/log/mattermost.log\"|\"FileLocation\": \"/var/log\"|g" "$config_file"
+ynh_replace_string --match_string "\"FileLocation\": \"/var/log/mattermost.log\"" --replace_string "\"FileLocation\": \"/var/log\"" --target_file "$config_file"
 
 # Move log files to a directory (rather than directly in /var/log)
 # See https://github.com/YunoHost-Apps/mattermost_ynh/issues/61
 mkdir -p "$logs_path"
-sed -i "s|\"FileLocation\": \"/var/log\"|\"FileLocation\": \"$logs_path\"|g" "$config_file"
+ynh_replace_string --match_string "\"FileLocation\": \"/var/log\"" --replace_string "\"FileLocation\": \"$logs_path\"" --target_file "$config_file"
 if [ -f "/var/log/${app}.log" ]; then
   mv "/var/log/${app}.log" "$logs_path/"
 fi