diff --git a/dnscrypt-wrapper.sh b/dnscrypt-wrapper.sh
index 9235a29..64a8f40 100755
--- a/dnscrypt-wrapper.sh
+++ b/dnscrypt-wrapper.sh
@@ -10,7 +10,7 @@ prune() {
 }
 
 rotation_needed() {
-    if [ $(/usr/bin/find "$STKEYS_DIR" -name '*.cert' -type f -cmin -720 -print -quit | wc -l | sed 's/[^0-9]//g') -le 0 ]; then
+    if [ "$(/usr/bin/find "$STKEYS_DIR" -name '*.cert' -type f -cmin -720 -print -quit | wc -l | sed 's/[^0-9]//g')" -le 0 ]; then
         echo true
     else
         echo false
@@ -54,7 +54,7 @@ provider_name=$(cat "$KEYS_DIR/provider_name")
 
 mkdir -p "$STKEYS_DIR"
 prune
-[ $(rotation_needed) = true ] && new_key
+[ "$(rotation_needed)" = true ] && new_key
 
 [ -r "$BLACKLIST" ] && blacklist_opt="--blacklist-file=${BLACKLIST}"
 
@@ -64,5 +64,5 @@ exec /opt/dnscrypt-wrapper/sbin/dnscrypt-wrapper \
     --resolver-address=127.0.0.1:553 \
     --provider-name="$provider_name" \
     --provider-cert-file="$(stcerts_files)" \
-    --crypt-secretkey-file=$(stkeys_files) \
+    --crypt-secretkey-file="$(stkeys_files)" \
     $blacklist_opt
diff --git a/entrypoint.sh b/entrypoint.sh
index c8743c5..85f0862 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -9,7 +9,7 @@ KEYS_DIR="/opt/dnscrypt-wrapper/etc/keys"
 # -N provider-name -E external-ip-address:port
 
 init() {
-    if [ $(is_initialized) = yes ]; then
+    if [ "$(is_initialized)" = yes ]; then
         start
         exit $?
     fi
@@ -65,7 +65,7 @@ provider_info() {
 }
 
 is_initialized() {
-    if [ ! -f "${KEYS_DIR}/public.key" -a ! -f "${KEYS_DIR}/secret.key" -a ! -f "${KEYS_DIR}/provider_name" ]; then
+    if [ ! -f "${KEYS_DIR}/public.key" ] && [ ! -f "${KEYS_DIR}/secret.key" ] && [ ! -f "${KEYS_DIR}/provider_name" ]; then
         echo no
     else
         echo yes
@@ -73,7 +73,7 @@ is_initialized() {
 }
 
 ensure_initialized() {
-    if [ $(is_initialized) = no ]; then
+    if [ "$(is_initialized)" = no ]; then
         echo "Please provide an initial configuration (init -N <provider_name> -E <external IP>)" >&2
         exit 1
     fi
diff --git a/key-rotation.sh b/key-rotation.sh
index 5f67c66..bfe7285 100755
--- a/key-rotation.sh
+++ b/key-rotation.sh
@@ -6,13 +6,13 @@ KEYS_DIR="/opt/dnscrypt-wrapper/etc/keys"
 STKEYS_DIR="${KEYS_DIR}/short-term"
 
 rotation_needed() {
-    if [ $(/usr/bin/find "$STKEYS_DIR" -type f -cmin -720 -print -quit | wc -l | sed 's/[^0-9]//g') -le 0 ]; then
+    if [ "$(/usr/bin/find "$STKEYS_DIR" -type f -cmin -720 -print -quit | wc -l | sed 's/[^0-9]//g')" -le 0 ]; then
         echo true
     else
         echo false
     fi
 }
 
-[ $(rotation_needed) = true ] || exit 0
-sv status dnscrypt-wrapper | egrep -q '^run:' || exit 0
+[ "$(rotation_needed)" = true ] || exit 0
+sv status dnscrypt-wrapper | grep -E -q '^run:' || exit 0
 sv restart dnscrypt-wrapper
diff --git a/unbound.sh b/unbound.sh
index 6cea2e7..c44c3a9 100755
--- a/unbound.sh
+++ b/unbound.sh
@@ -4,17 +4,17 @@ KEYS_DIR="/opt/dnscrypt-wrapper/etc/keys"
 ZONES_DIR="/opt/unbound/etc/unbound/zones"
 
 reserved=12582912
-availableMemory=$((1024 * $( (fgrep MemAvailable /proc/meminfo || fgrep MemTotal /proc/meminfo) | sed 's/[^0-9]//g' ) ))
-if [ $availableMemory -le $(($reserved * 2)) ]; then
+availableMemory=$((1024 * $( (grep -F MemAvailable /proc/meminfo || grep -F MemTotal /proc/meminfo) | sed 's/[^0-9]//g' ) ))
+if [ $availableMemory -le $((reserved * 2)) ]; then
     echo "Not enough memory" >&2
     exit 1
 fi
-availableMemory=$(($availableMemory - $reserved))
-msg_cache_size=$(($availableMemory / 3))
-rr_cache_size=$(($availableMemory / 3))
+availableMemory=$((availableMemory - reserved))
+msg_cache_size=$((availableMemory / 3))
+rr_cache_size=$((availableMemory / 3))
 nproc=$(nproc)
-if [ $nproc -gt 1 ]; then
-    threads=$(($nproc - 1))
+if [ "$nproc" -gt 1 ]; then
+    threads=$((nproc - 1))
 else
     threads=1
 fi