diff --git a/setup/bootstrap.sh b/setup/bootstrap.sh
index db6ce25f..b596a070 100644
--- a/setup/bootstrap.sh
+++ b/setup/bootstrap.sh
@@ -63,10 +63,10 @@ if [ ! -d "$HOME/mailinabox" ]; then
 		SOURCE=https://github.com/mail-in-a-box/mailinabox
 	fi
 
-	echo Downloading Mail-in-a-Box $TAG. . .
+	echo "Downloading Mail-in-a-Box $TAG. . ."
 	git clone \
-		-b $TAG --depth 1 \
-		$SOURCE \
+		-b "$TAG" --depth 1 \
+		"$SOURCE" \
 		"$HOME/mailinabox" \
 		< /dev/null 2> /dev/null
 
@@ -78,9 +78,9 @@ cd "$HOME/mailinabox" || exit
 
 # Update it.
 if [ "$TAG" != $(git describe --always) ]; then
-	echo Updating Mail-in-a-Box to $TAG . . .
-	git fetch --depth 1 --force --prune origin tag $TAG
-	if ! git checkout -q $TAG; then
+	echo "Updating Mail-in-a-Box to $TAG . . ."
+	git fetch --depth 1 --force --prune origin tag "$TAG"
+	if ! git checkout -q "$TAG"; then
 		echo "Update failed. Did you modify something in $(pwd)?"
 		exit 1
 	fi
diff --git a/setup/firstuser.sh b/setup/firstuser.sh
index ffec7064..540c565f 100644
--- a/setup/firstuser.sh
+++ b/setup/firstuser.sh
@@ -47,7 +47,7 @@ if [ -z "$(management/cli.py user)" ]; then
 	fi
 
 	# Create the user's mail account. This will ask for a password if none was given above.
-	management/cli.py user add "$EMAIL_ADDR" ${EMAIL_PW:-}
+	management/cli.py user add "$EMAIL_ADDR" "${EMAIL_PW:-}"
 
 	# Make it an admin.
 	hide_output management/cli.py user make-admin "$EMAIL_ADDR"
diff --git a/setup/functions.sh b/setup/functions.sh
index 84156b9f..8e8b79e2 100644
--- a/setup/functions.sh
+++ b/setup/functions.sh
@@ -62,9 +62,9 @@ function get_default_hostname {
 	# Guess the machine's hostname. It should be a fully qualified
 	# domain name suitable for DNS. None of these calls may provide
 	# the right value, but it's the best guess we can make.
-	set -- $(hostname --fqdn      2>/dev/null ||
+	set -- "$(hostname --fqdn      2>/dev/null ||
                  hostname --all-fqdns 2>/dev/null ||
-                 hostname             2>/dev/null)
+                 hostname             2>/dev/null)"
 	printf '%s\n' "$1" # return this value
 }
 
diff --git a/setup/munin.sh b/setup/munin.sh
index cebecf80..56cdb391 100755
--- a/setup/munin.sh
+++ b/setup/munin.sh
@@ -62,7 +62,7 @@ done
 mkdir -p /var/lib/munin-node/plugin-state/
 
 # Create a systemd service for munin.
-ln -sf $(pwd)/management/munin_start.sh /usr/local/lib/mailinabox/munin_start.sh
+ln -sf "$(pwd)/management/munin_start.sh" /usr/local/lib/mailinabox/munin_start.sh
 chmod 0744 /usr/local/lib/mailinabox/munin_start.sh
 cp --remove-destination conf/munin.service /lib/systemd/system/munin.service # target was previously a symlink so remove first
 hide_output systemctl link -f /lib/systemd/system/munin.service
diff --git a/setup/nextcloud.sh b/setup/nextcloud.sh
index 95cc43f1..4b0b881b 100755
--- a/setup/nextcloud.sh
+++ b/setup/nextcloud.sh
@@ -48,13 +48,13 @@ user_external_hash=a494073dcdecbbbc79a9c77f72524ac9994d2eec
 
 apt-get purge -qq -y owncloud* # we used to use the package manager
 
-apt_install curl php${PHP_VER} php${PHP_VER}-fpm \
-	php${PHP_VER}-cli php${PHP_VER}-sqlite3 php${PHP_VER}-gd php${PHP_VER}-imap php${PHP_VER}-curl \
-	php${PHP_VER}-dev php${PHP_VER}-gd php${PHP_VER}-xml php${PHP_VER}-mbstring php${PHP_VER}-zip php${PHP_VER}-apcu \
-	php${PHP_VER}-intl php${PHP_VER}-imagick php${PHP_VER}-gmp php${PHP_VER}-bcmath
+apt_install curl php"${PHP_VER}" php"${PHP_VER}"-fpm \
+	php"${PHP_VER}"-cli php"${PHP_VER}"-sqlite3 php"${PHP_VER}"-gd php"${PHP_VER}"-imap php"${PHP_VER}"-curl \
+	php"${PHP_VER}"-dev php"${PHP_VER}"-gd php"${PHP_VER}"-xml php"${PHP_VER}"-mbstring php"${PHP_VER}"-zip php"${PHP_VER}"-apcu \
+	php"${PHP_VER}"-intl php"${PHP_VER}"-imagick php"${PHP_VER}"-gmp php"${PHP_VER}"-bcmath
 
 # Enable APC before Nextcloud tools are run.
-tools/editconf.py /etc/php/$PHP_VER/mods-available/apcu.ini -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/mods-available/apcu.ini -c ';' \
 	apc.enabled=1 \
 	apc.enable_cli=1
 
@@ -121,21 +121,21 @@ InstallNextcloud() {
 	if [ -e "$STORAGE_ROOT/owncloud/owncloud.db" ]; then
 		# ownCloud 8.1.1 broke upgrades. It may fail on the first attempt, but
 		# that can be OK.
-		sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ upgrade
+		sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ upgrade
 		if [ \( $? -ne 0 \) -a \( $? -ne 3 \) ]; then
 			echo "Trying ownCloud upgrade again to work around ownCloud upgrade bug..."
-			sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ upgrade
+			sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ upgrade
 			if [ \( $? -ne 0 \) -a \( $? -ne 3 \) ]; then exit 1; fi
-			sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ maintenance:mode --off
+			sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ maintenance:mode --off
 			echo "...which seemed to work."
 		fi
 
 		# Add missing indices. NextCloud didn't include this in the normal upgrade because it might take some time.
-		sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ db:add-missing-indices
-		sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ db:add-missing-primary-keys
+		sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ db:add-missing-indices
+		sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ db:add-missing-primary-keys
 
 		# Run conversion to BigInt identifiers, this process may take some time on large tables.
-		sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ db:convert-filecache-bigint --no-interaction
+		sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ db:convert-filecache-bigint --no-interaction
 	fi
 }
 
@@ -147,7 +147,7 @@ InstallNextcloud() {
 
 # If config.php exists, get version number, otherwise CURRENT_NEXTCLOUD_VER is empty.
 if [ -f "$STORAGE_ROOT/owncloud/config.php" ]; then
-	CURRENT_NEXTCLOUD_VER=$(php$PHP_VER -r "include(\"$STORAGE_ROOT/owncloud/config.php\"); echo(\$CONFIG['version']);")
+	CURRENT_NEXTCLOUD_VER=$(php"$PHP_VER" -r "include(\"$STORAGE_ROOT/owncloud/config.php\"); echo(\$CONFIG['version']);")
 else
 	CURRENT_NEXTCLOUD_VER=""
 fi
@@ -157,7 +157,7 @@ fi
 if [ ! -d /usr/local/lib/owncloud/ ] || [[ ! ${CURRENT_NEXTCLOUD_VER} =~ ^$nextcloud_ver ]]; then
 
 	# Stop php-fpm if running. If they are not running (which happens on a previously failed install), dont bail.
-	service php$PHP_VER-fpm stop &> /dev/null || /bin/true
+	service php"$PHP_VER"-fpm stop &> /dev/null || /bin/true
 
 	# Backup the existing ownCloud/Nextcloud.
 	# Create a backup directory to store the current installation and database to
@@ -284,7 +284,7 @@ EOF
 	# Execute Nextcloud's setup step, which creates the Nextcloud sqlite database.
 	# It also wipes it if it exists. And it updates config.php with database
 	# settings and deletes the autoconfig.php file.
-	(cd /usr/local/lib/owncloud; sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/index.php;)
+	(cd /usr/local/lib/owncloud; sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/index.php;)
 fi
 
 # Update config.php.
@@ -300,7 +300,7 @@ fi
 # Use PHP to read the settings file, modify it, and write out the new settings array.
 TIMEZONE=$(cat /etc/timezone)
 CONFIG_TEMP=$(/bin/mktemp)
-php$PHP_VER <<EOF > "$CONFIG_TEMP" && mv "$CONFIG_TEMP" "$STORAGE_ROOT/owncloud/config.php";
+php"$PHP_VER" <<EOF > "$CONFIG_TEMP" && mv "$CONFIG_TEMP" "$STORAGE_ROOT/owncloud/config.php";
 <?php
 include("$STORAGE_ROOT/owncloud/config.php");
 
@@ -337,25 +337,25 @@ chown www-data:www-data "$STORAGE_ROOT/owncloud/config.php"
 # The firstrunwizard gave Josh all sorts of problems, so disabling that.
 # user_external is what allows Nextcloud to use IMAP for login. The contacts
 # and calendar apps are the extensions we really care about here.
-hide_output sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/console.php app:disable firstrunwizard
-hide_output sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/console.php app:enable user_external
-hide_output sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/console.php app:enable contacts
-hide_output sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/console.php app:enable calendar
+hide_output sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/console.php app:disable firstrunwizard
+hide_output sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/console.php app:enable user_external
+hide_output sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/console.php app:enable contacts
+hide_output sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/console.php app:enable calendar
 
 # When upgrading, run the upgrade script again now that apps are enabled. It seems like
 # the first upgrade at the top won't work because apps may be disabled during upgrade?
 # Check for success (0=ok, 3=no upgrade needed).
-sudo -u www-data php$PHP_VER /usr/local/lib/owncloud/occ upgrade
+sudo -u www-data php"$PHP_VER" /usr/local/lib/owncloud/occ upgrade
 if [ \( $? -ne 0 \) -a \( $? -ne 3 \) ]; then exit 1; fi
 
 # Disable default apps that we don't support
 sudo -u www-data \
-	php$PHP_VER /usr/local/lib/owncloud/occ app:disable photos dashboard activity \
+	php"$PHP_VER" /usr/local/lib/owncloud/occ app:disable photos dashboard activity \
 	| (grep -v "No such app enabled" || /bin/true)
 
 # Set PHP FPM values to support large file uploads
 # (semicolon is the comment character in this file, hashes produce deprecation warnings)
-tools/editconf.py /etc/php/$PHP_VER/fpm/php.ini -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/fpm/php.ini -c ';' \
 	upload_max_filesize=16G \
 	post_max_size=16G \
 	output_buffering=16384 \
@@ -364,7 +364,7 @@ tools/editconf.py /etc/php/$PHP_VER/fpm/php.ini -c ';' \
 	short_open_tag=On
 
 # Set Nextcloud recommended opcache settings
-tools/editconf.py /etc/php/$PHP_VER/cli/conf.d/10-opcache.ini -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/cli/conf.d/10-opcache.ini -c ';' \
 	opcache.enable=1 \
 	opcache.enable_cli=1 \
 	opcache.interned_strings_buffer=8 \
@@ -393,7 +393,7 @@ chmod +x /etc/cron.d/mailinabox-nextcloud
 
 # We also need to change the sending mode from background-job to occ.
 # Or else the reminders will just be sent as soon as possible when the background jobs run.
-hide_output sudo -u www-data php$PHP_VER -f /usr/local/lib/owncloud/occ config:app:set dav sendEventRemindersMode --value occ
+hide_output sudo -u www-data php"$PHP_VER" -f /usr/local/lib/owncloud/occ config:app:set dav sendEventRemindersMode --value occ
 
 # Now set the config to read-only.
 # Do this only at the very bottom when no further occ commands are needed.
@@ -422,4 +422,4 @@ EOF
 # ```
 
 # Enable PHP modules and restart PHP.
-restart_service php$PHP_VER-fpm
+restart_service php"$PHP_VER"-fpm
diff --git a/setup/questions.sh b/setup/questions.sh
index 496bd1d2..e7803363 100644
--- a/setup/questions.sh
+++ b/setup/questions.sh
@@ -207,6 +207,6 @@ if [ "$PRIVATE_IPV6" != "$PUBLIC_IPV6" ]; then
 	echo "Private IPv6 Address: $PRIVATE_IPV6"
 fi
 if [ -f /usr/bin/git ] && [ -d .git ]; then
-	echo "Mail-in-a-Box Version: " $(git describe --always)
+	echo "Mail-in-a-Box Version: $(git describe --always)"
 fi
 echo
diff --git a/setup/web.sh b/setup/web.sh
index 8017df90..6969c6ce 100755
--- a/setup/web.sh
+++ b/setup/web.sh
@@ -19,7 +19,7 @@ fi
 
 echo "Installing Nginx (web server)..."
 
-apt_install nginx php${PHP_VER}-cli php${PHP_VER}-fpm idn2
+apt_install nginx php"${PHP_VER}"-cli php"${PHP_VER}"-fpm idn2
 
 rm -f /etc/nginx/sites-enabled/default
 
@@ -46,15 +46,15 @@ tools/editconf.py /etc/nginx/nginx.conf -s \
 	ssl_protocols="TLSv1.2 TLSv1.3;"
 
 # Tell PHP not to expose its version number in the X-Powered-By header.
-tools/editconf.py /etc/php/$PHP_VER/fpm/php.ini -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/fpm/php.ini -c ';' \
 	expose_php=Off
 
 # Set PHPs default charset to UTF-8, since we use it. See #367.
-tools/editconf.py /etc/php/$PHP_VER/fpm/php.ini -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/fpm/php.ini -c ';' \
         default_charset="UTF-8"
 
 # Configure the path environment for php-fpm
-tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
+tools/editconf.py /etc/php/"$PHP_VER"/fpm/pool.d/www.conf -c ';' \
 	env[PATH]=/usr/local/bin:/usr/bin:/bin \
 
 # Configure php-fpm based on the amount of memory the machine has
@@ -64,7 +64,7 @@ tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
 TOTAL_PHYSICAL_MEM=$(head -n 1 /proc/meminfo | awk '{print $2}' || /bin/true)
 if [ "$TOTAL_PHYSICAL_MEM" -lt 1000000 ]
 then
-        tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
+        tools/editconf.py /etc/php/"$PHP_VER"/fpm/pool.d/www.conf -c ';' \
                 pm=ondemand \
                 pm.max_children=8 \
                 pm.start_servers=2 \
@@ -72,7 +72,7 @@ then
                 pm.max_spare_servers=3
 elif [ "$TOTAL_PHYSICAL_MEM" -lt 2000000 ]
 then
-        tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
+        tools/editconf.py /etc/php/"$PHP_VER"/fpm/pool.d/www.conf -c ';' \
                 pm=ondemand \
                 pm.max_children=16 \
                 pm.start_servers=4 \
@@ -80,14 +80,14 @@ then
                 pm.max_spare_servers=6
 elif [ "$TOTAL_PHYSICAL_MEM" -lt 3000000 ]
 then
-        tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
+        tools/editconf.py /etc/php/"$PHP_VER"/fpm/pool.d/www.conf -c ';' \
                 pm=dynamic \
                 pm.max_children=60 \
                 pm.start_servers=6 \
                 pm.min_spare_servers=3 \
                 pm.max_spare_servers=9
 else
-        tools/editconf.py /etc/php/$PHP_VER/fpm/pool.d/www.conf -c ';' \
+        tools/editconf.py /etc/php/"$PHP_VER"/fpm/pool.d/www.conf -c ';' \
                 pm=dynamic \
                 pm.max_children=120 \
                 pm.start_servers=12 \
@@ -147,7 +147,7 @@ chown -R "$STORAGE_USER" "$STORAGE_ROOT/www"
 
 # Start services.
 restart_service nginx
-restart_service php$PHP_VER-fpm
+restart_service php"$PHP_VER"-fpm
 
 # Open ports.
 ufw_allow http
diff --git a/setup/webmail.sh b/setup/webmail.sh
index 41e611c3..a2351c31 100755
--- a/setup/webmail.sh
+++ b/setup/webmail.sh
@@ -22,8 +22,8 @@ source /etc/mailinabox.conf # load global vars
 echo "Installing Roundcube (webmail)..."
 apt_install \
 	dbconfig-common \
-	php${PHP_VER}-cli php${PHP_VER}-sqlite3 php${PHP_VER}-intl php${PHP_VER}-common php${PHP_VER}-curl php${PHP_VER}-imap \
-	php${PHP_VER}-gd php${PHP_VER}-pspell php${PHP_VER}-mbstring libjs-jquery libjs-jquery-mousewheel libmagic1 \
+	php"${PHP_VER}"-cli php"${PHP_VER}"-sqlite3 php"${PHP_VER}"-intl php"${PHP_VER}"-common php"${PHP_VER}"-curl php"${PHP_VER}"-imap \
+	php"${PHP_VER}"-gd php"${PHP_VER}"-pspell php"${PHP_VER}"-mbstring libjs-jquery libjs-jquery-mousewheel libmagic1 \
 	sqlite3
 
 # Install Roundcube from source if it is not already present or if it is out of date.
@@ -205,7 +205,7 @@ chown -f -R root:www-data ${RCM_PLUGIN_DIR}/carddav
 chmod -R 774 ${RCM_PLUGIN_DIR}/carddav
 
 # Run Roundcube database migration script (database is created if it does not exist)
-php$PHP_VER ${RCM_DIR}/bin/updatedb.sh --dir ${RCM_DIR}/SQL --package roundcube
+php"$PHP_VER" ${RCM_DIR}/bin/updatedb.sh --dir ${RCM_DIR}/SQL --package roundcube
 chown www-data:www-data "$STORAGE_ROOT/mail/roundcube/roundcube.sqlite"
 chmod 664 "$STORAGE_ROOT/mail/roundcube/roundcube.sqlite"
 
@@ -220,5 +220,5 @@ sed -i.miabold 's/^[^#]\+.\+PRAGMA journal_mode = WAL.\+$/#&/' \
 sqlite3 "$STORAGE_ROOT/mail/roundcube/roundcube.sqlite" 'PRAGMA journal_mode=WAL;'
 
 # Enable PHP modules.
-phpenmod -v $PHP_VER imap
-restart_service php$PHP_VER-fpm
+phpenmod -v "$PHP_VER" imap
+restart_service php"$PHP_VER"-fpm
diff --git a/setup/zpush.sh b/setup/zpush.sh
index 152418c0..e46d72f1 100755
--- a/setup/zpush.sh
+++ b/setup/zpush.sh
@@ -17,9 +17,9 @@ source /etc/mailinabox.conf # load global vars
 
 echo "Installing Z-Push (Exchange/ActiveSync server)..."
 apt_install \
-       php${PHP_VER}-soap php${PHP_VER}-imap libawl-php php$PHP_VER-xml
+       php"${PHP_VER}"-soap php"${PHP_VER}"-imap libawl-php php"$PHP_VER"-xml
 
-phpenmod -v $PHP_VER imap
+phpenmod -v "$PHP_VER" imap
 
 # Copy Z-Push into place.
 VERSION=2.7.1
@@ -44,10 +44,10 @@ if [ $needs_update == 1 ]; then
 	# Create admin and top scripts with PHP_VER  
 	rm -f /usr/sbin/z-push-{admin,top}
     echo '#!/bin/bash' > /usr/sbin/z-push-admin
-    echo php$PHP_VER /usr/local/lib/z-push/z-push-admin.php '"$@"' >> /usr/sbin/z-push-admin
+    echo php"$PHP_VER" /usr/local/lib/z-push/z-push-admin.php '"$@"' >> /usr/sbin/z-push-admin
     chmod 755 /usr/sbin/z-push-admin
     echo '#!/bin/bash' > /usr/sbin/z-push-top
-    echo php$PHP_VER /usr/local/lib/z-push/z-push-top.php '"$@"' >> /usr/sbin/z-push-top
+    echo php"$PHP_VER" /usr/local/lib/z-push/z-push-top.php '"$@"' >> /usr/sbin/z-push-top
     chmod 755 /usr/sbin/z-push-top
 	
 	echo $VERSION > /usr/local/lib/z-push/version
@@ -108,8 +108,8 @@ EOF
 
 # Restart service.
 
-restart_service php$PHP_VER-fpm
+restart_service php"$PHP_VER"-fpm
 
 # Fix states after upgrade
 
-hide_output php$PHP_VER /usr/local/lib/z-push/z-push-admin.php -a fixstates
+hide_output php"$PHP_VER" /usr/local/lib/z-push/z-push-admin.php -a fixstates
diff --git a/tools/dns_update b/tools/dns_update
index 947c3dd1..2bbcce67 100755
--- a/tools/dns_update
+++ b/tools/dns_update
@@ -3,4 +3,4 @@ POSTDATA=dummy
 if [ "$1" == "--force" ]; then
 	POSTDATA=force=1
 fi
-curl -s -d $POSTDATA --user $(</var/lib/mailinabox/api.key): http://127.0.0.1:10222/dns/update
+curl -s -d $POSTDATA --user "$(</var/lib/mailinabox/api.key):" http://127.0.0.1:10222/dns/update
diff --git a/tools/web_update b/tools/web_update
index c4b096d9..719484a8 100755
--- a/tools/web_update
+++ b/tools/web_update
@@ -1,2 +1,2 @@
 #!/bin/bash
-curl -s -d POSTDATA --user $(</var/lib/mailinabox/api.key): http://127.0.0.1:10222/web/update
+curl -s -d POSTDATA --user "$(</var/lib/mailinabox/api.key):" http://127.0.0.1:10222/web/update