diff --git a/scripts/backup b/scripts/backup
index e88426f..bc978f0 100644
--- a/scripts/backup
+++ b/scripts/backup
@@ -1,8 +1,10 @@
 #!/bin/bash
 
-# Retrieve arguments
-backup_dir=$1
-app=$2
+# Exit on command errors and treat unset variables as an error
+set -eu
+
+# Retrieve app id
+app=$YNH_APP_INSTANCE_NAME
 
 # Set app specific variables
 dbname=$app
diff --git a/scripts/install b/scripts/install
index a91bbd6..74c1aeb 100644
--- a/scripts/install
+++ b/scripts/install
@@ -1,15 +1,18 @@
 #!/bin/bash
 
-set -e
+# Exit on command errors and treat unset variables as an error
+set -eu
+
+# Retrieve app id
+app=$YNH_APP_INSTANCE_NAME
 
 # Retrieve arguments
 domain=$1
 path=${2%/}
 password=$3
-app=${!#}
 
 # Load common variables and helpers
-source ./_common.sh
+. ./_common.sh
 
 # Set app specific variables
 dbname=$app
diff --git a/scripts/remove b/scripts/remove
index 0b0af86..ae74e55 100644
--- a/scripts/remove
+++ b/scripts/remove
@@ -1,21 +1,21 @@
 #!/bin/bash
 
-# Retrieve arguments
-app=${!#}
+# Retrieve app id
+app=$YNH_APP_INSTANCE_NAME
 
 # Load common variables and helpers
-source ./_common.sh
+. ./_common.sh
 
 # Set app specific variables
 dbname=$app
 dbuser=$app
 
 # Drop MySQL database and user
-ynh_mysql_drop_db $dbname || true
-ynh_mysql_drop_user $dbuser || true
+ynh_mysql_drop_db "$dbname" 2>/dev/null || true
+ynh_mysql_drop_user "$dbuser" 2>/dev/null || true
 
 # Retrieve domain from app settings
-domain=$(ynh_app_setting_get $app domain)
+domain=$(ynh_app_setting_get "$app" domain)
 
 # Delete app directory and configurations
 sudo rm -rf "/var/www/${app}"
diff --git a/scripts/restore b/scripts/restore
index bb43be9..e394c7f 100644
--- a/scripts/restore
+++ b/scripts/restore
@@ -1,12 +1,10 @@
 #!/bin/bash
 
-# Retrieve arguments
-backup_dir=$1
-app=$2
+# Exit on command errors and treat unset variables as an error
+set -eu
 
-# Set app specific variables
-dbname=$app
-dbuser=$app
+# Retrieve app id
+app=$YNH_APP_INSTANCE_NAME
 
 # Source app helpers
 . /usr/share/yunohost/helpers
@@ -16,6 +14,10 @@ domain=$(ynh_app_setting_get "$app" domain)
 path=$(ynh_app_setting_get "$app" path)
 dbpass=$(ynh_app_setting_get "$app" mysqlpwd)
 
+# Set app specific variables
+dbname=$app
+dbuser=$app
+
 # Check domain/path availability
 sudo yunohost app checkurl "${domain}${path}" -a "$app" \
   || exit 1
diff --git a/scripts/upgrade b/scripts/upgrade
index 2897a13..35491a1 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -1,20 +1,23 @@
 #!/bin/bash
 
-set -u
+# Exit on command errors and treat unset variables as an error
+set -eu
+
+# Retrieve app id
+app=$YNH_APP_INSTANCE_NAME
 
 # Load common variables and helpers
 . ./_common.sh
 
-# Set app specific variables
-app=${!#}
-dbname=$app
-dbuser=$app
-
-# Retrieve arguments
+# Retrieve app settings
 domain=$(ynh_app_setting_get "$app" domain)
 path=$(ynh_app_setting_get "$app" path)
 path=${path%/}
 
+# Set app specific variables
+dbname=$app
+dbuser=$app
+
 # Check destination directory
 DESTDIR="/var/www/$app"
 [[ ! -d $DESTDIR ]] && ynh_die \