diff --git a/extras/ikev2setup.sh b/extras/ikev2setup.sh
index 8ba7d5d..9ae8a38 100755
--- a/extras/ikev2setup.sh
+++ b/extras/ikev2setup.sh
@@ -60,15 +60,16 @@ check_os() {
     elif grep -q "release 8" "$rh_file"; then
       os_ver=8
       grep -qi stream "$rh_file" && os_ver=8s
-      if [ "$os_type$os_ver" = "centos8" ]; then
-        exiterr "CentOS Linux 8 is EOL and not supported."
-      fi
     elif grep -q "release 9" "$rh_file"; then
       os_ver=9
       grep -qi stream "$rh_file" && os_ver=9s
     else
       exiterr "This script only supports CentOS/RHEL 7-9."
     fi
+    if [ "$os_type" = "centos" ] \
+      && { [ "$os_ver" = 7 ] || [ "$os_ver" = 8 ] || [ "$os_ver" = 8s ]; }; then
+      exiterr "CentOS Linux $os_ver is EOL and not supported."
+    fi
   elif grep -qs "Amazon Linux release 2 " /etc/system-release; then
     os_type=amzn
     os_ver=2
@@ -99,8 +100,8 @@ EOF
     esac
     if [ "$os_type" = "alpine" ]; then
       os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
-      if [ "$os_ver" != "3.18" ] && [ "$os_ver" != "3.19" ]; then
-        exiterr "This script only supports Alpine Linux 3.18/3.19."
+      if [ "$os_ver" != "3.19" ] && [ "$os_ver" != "3.20" ]; then
+        exiterr "This script only supports Alpine Linux 3.19/3.20."
       fi
     else
       os_ver=$(sed 's/\..*//' /etc/debian_version | tr -dc 'A-Za-z0-9')
@@ -168,7 +169,7 @@ confirm_or_abort() {
 show_header() {
 cat <<'EOF'
 
-IKEv2 Script   Copyright (c) 2020-2024 Lin Song   14 Apr 2024
+IKEv2 Script   Copyright (c) 2020-2024 Lin Song   28 Jul 2024
 
 EOF
 }
diff --git a/extras/vpnupgrade.sh b/extras/vpnupgrade.sh
index f3e614f..179dfa0 100755
--- a/extras/vpnupgrade.sh
+++ b/extras/vpnupgrade.sh
@@ -51,15 +51,16 @@ check_os() {
     elif grep -q "release 8" "$rh_file"; then
       os_ver=8
       grep -qi stream "$rh_file" && os_ver=8s
-      if [ "$os_type$os_ver" = "centos8" ]; then
-        exiterr "CentOS Linux 8 is EOL and not supported."
-      fi
     elif grep -q "release 9" "$rh_file"; then
       os_ver=9
       grep -qi stream "$rh_file" && os_ver=9s
     else
       exiterr "This script only supports CentOS/RHEL 7-9."
     fi
+    if [ "$os_type" = "centos" ] \
+      && { [ "$os_ver" = 7 ] || [ "$os_ver" = 8 ] || [ "$os_ver" = 8s ]; }; then
+      exiterr "CentOS Linux $os_ver is EOL and not supported."
+    fi
   elif grep -qs "Amazon Linux release 2 " /etc/system-release; then
     os_type=amzn
     os_ver=2
@@ -90,8 +91,8 @@ EOF
     esac
     if [ "$os_type" = "alpine" ]; then
       os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
-      if [ "$os_ver" != "3.18" ] && [ "$os_ver" != "3.19" ]; then
-        exiterr "This script only supports Alpine Linux 3.18/3.19."
+      if [ "$os_ver" != "3.19" ] && [ "$os_ver" != "3.20" ]; then
+        exiterr "This script only supports Alpine Linux 3.19/3.20."
       fi
     else
       os_ver=$(sed 's/\..*//' /etc/debian_version | tr -dc 'A-Za-z0-9')
diff --git a/extras/vpnupgrade_alpine.sh b/extras/vpnupgrade_alpine.sh
index 2588a69..ded221a 100755
--- a/extras/vpnupgrade_alpine.sh
+++ b/extras/vpnupgrade_alpine.sh
@@ -51,8 +51,8 @@ check_os() {
       ;;
   esac
   os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
-  if [ "$os_ver" != "3.18" ] && [ "$os_ver" != "3.19" ]; then
-    exiterr "This script only supports Alpine Linux 3.18/3.19."
+  if [ "$os_ver" != "3.19" ] && [ "$os_ver" != "3.20" ]; then
+    exiterr "This script only supports Alpine Linux 3.19/3.20."
   fi
 }
 
diff --git a/extras/vpnupgrade_centos.sh b/extras/vpnupgrade_centos.sh
index 2377f40..e724d65 100755
--- a/extras/vpnupgrade_centos.sh
+++ b/extras/vpnupgrade_centos.sh
@@ -54,15 +54,16 @@ check_os() {
     elif grep -q "release 8" "$rh_file"; then
       os_ver=8
       grep -qi stream "$rh_file" && os_ver=8s
-      if [ "$os_type$os_ver" = "centos8" ]; then
-        exiterr "CentOS Linux 8 is EOL and not supported."
-      fi
     elif grep -q "release 9" "$rh_file"; then
       os_ver=9
       grep -qi stream "$rh_file" && os_ver=9s
     else
       exiterr "This script only supports CentOS/RHEL 7-9."
     fi
+    if [ "$os_type" = "centos" ] \
+      && { [ "$os_ver" = 7 ] || [ "$os_ver" = 8 ] || [ "$os_ver" = 8s ]; }; then
+      exiterr "CentOS Linux $os_ver is EOL and not supported."
+    fi
   else
 cat 1>&2 <<'EOF'
 Error: This script only supports one of the following OS:
diff --git a/vpnsetup.sh b/vpnsetup.sh
index 814b092..7dba9ca 100755
--- a/vpnsetup.sh
+++ b/vpnsetup.sh
@@ -81,15 +81,16 @@ check_os() {
     elif grep -q "release 8" "$rh_file"; then
       os_ver=8
       grep -qi stream "$rh_file" && os_ver=8s
-      if [ "$os_type$os_ver" = "centos8" ]; then
-        exiterr "CentOS Linux 8 is EOL and not supported."
-      fi
     elif grep -q "release 9" "$rh_file"; then
       os_ver=9
       grep -qi stream "$rh_file" && os_ver=9s
     else
       exiterr "This script only supports CentOS/RHEL 7-9."
     fi
+    if [ "$os_type" = "centos" ] \
+      && { [ "$os_ver" = 7 ] || [ "$os_ver" = 8 ] || [ "$os_ver" = 8s ]; }; then
+      exiterr "CentOS Linux $os_ver is EOL and not supported."
+    fi
   elif grep -qs "Amazon Linux release 2 " /etc/system-release; then
     os_type=amzn
     os_ver=2
@@ -122,8 +123,8 @@ EOF
     esac
     if [ "$os_type" = "alpine" ]; then
       os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
-      if [ "$os_ver" != "3.18" ] && [ "$os_ver" != "3.19" ]; then
-        exiterr "This script only supports Alpine Linux 3.18/3.19."
+      if [ "$os_ver" != "3.19" ] && [ "$os_ver" != "3.20" ]; then
+        exiterr "This script only supports Alpine Linux 3.19/3.20."
       fi
     else
       os_ver=$(sed 's/\..*//' /etc/debian_version | tr -dc 'A-Za-z0-9')
diff --git a/vpnsetup_alpine.sh b/vpnsetup_alpine.sh
index 2185fbc..c7a8d4d 100755
--- a/vpnsetup_alpine.sh
+++ b/vpnsetup_alpine.sh
@@ -70,8 +70,8 @@ check_os() {
       ;;
   esac
   os_ver=$(. /etc/os-release && printf '%s' "$VERSION_ID" | cut -d '.' -f 1,2)
-  if [ "$os_ver" != "3.18" ] && [ "$os_ver" != "3.19" ]; then
-    exiterr "This script only supports Alpine Linux 3.18/3.19."
+  if [ "$os_ver" != "3.19" ] && [ "$os_ver" != "3.20" ]; then
+    exiterr "This script only supports Alpine Linux 3.19/3.20."
   fi
 }
 
diff --git a/vpnsetup_centos.sh b/vpnsetup_centos.sh
index 87a81c7..810dae7 100755
--- a/vpnsetup_centos.sh
+++ b/vpnsetup_centos.sh
@@ -86,15 +86,16 @@ check_os() {
     elif grep -q "release 8" "$rh_file"; then
       os_ver=8
       grep -qi stream "$rh_file" && os_ver=8s
-      if [ "$os_type$os_ver" = "centos8" ]; then
-        exiterr "CentOS Linux 8 is EOL and not supported."
-      fi
     elif grep -q "release 9" "$rh_file"; then
       os_ver=9
       grep -qi stream "$rh_file" && os_ver=9s
     else
       exiterr "This script only supports CentOS/RHEL 7-9."
     fi
+    if [ "$os_type" = "centos" ] \
+      && { [ "$os_ver" = 7 ] || [ "$os_ver" = 8 ] || [ "$os_ver" = 8s ]; }; then
+      exiterr "CentOS Linux $os_ver is EOL and not supported."
+    fi
   else
 cat 1>&2 <<'EOF'
 Error: This script only supports one of the following OS: