diff --git a/kvmapp/system/init.d/S30eth b/kvmapp/system/init.d/S30eth
index 17db97f..604a673 100755
--- a/kvmapp/system/init.d/S30eth
+++ b/kvmapp/system/init.d/S30eth
@@ -1,119 +1,67 @@
 #!/bin/sh
 
-. /etc/profile
+RESERVE_INET="192.168.90.1/22"
 
-# /boot/eth.nodhcp for example
-# ipaddr/net        gw[optional]
-# 192.168.0.101/24 192.168.0.1
-# 192.168.3.116/22  
+clean_line() {
+    echo "$1" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//;s/\r//g'
+}
 
-RESERVE_INET="192.168.0.1/24"
+calc_gw() {
+    addr="$1"
+    netid="$2"
+    IFS=. read a b c d <<EOF
+$addr
+EOF
+    ipnum=$(( (a<<24) + (b<<16) + (c<<8) + d ))
+    mask=$(( 0xFFFFFFFF << (32-netid) & 0xFFFFFFFF ))
+    gwnum=$(( (ipnum & mask) | 1 ))
+    echo "$(( (gwnum>>24)&255 )).$(( (gwnum>>16)&255 )).$(( (gwnum>>8)&255 )).$(( gwnum&255 ))"
+}
 
 start() {
-    printf "start ethernet: "
-    if [ -e /boot/eth.nodhcp ] 
-    then
-        [ -e /boot/eth.nodhcp ] &&
-            cat /boot/eth.nodhcp | while read inet gw
-            do
-                addr=${inet%/*}
-                netid=${inet#*/}
-                [ -z $gw ] &&
-                gw=$( echo $addr| ( IFS='.' read a b c d; echo $((
-                    (((((($a<<8)+$b)<<8)+$c)<<8)+$d)
-                        & (((1<<$netid)-1)<<(32-$netid))
-                    ))
-                )) &&
-                gw=$(($gw>>24&0xff)).$(($gw>>16&0xff)).$(($gw>>8&0xff)).$((1+( $gw>>0&0xff )))
+    if [ -e /boot/eth.nodhcp ]; then
+        while IFS= read -r line || [ -n "$line" ]; do
+            line=$(clean_line "$line")
+            [ -z "$line" ] && continue
+            set -- $line
+            inet="$1"
+            gw="$2"
+            [ -z "$inet" ] && continue
+            addr=${inet%/*}
+            netid=${inet#*/}
+            [ -z "$gw" ] && gw=$(calc_gw "$addr" "$netid")
+            arping -Dqc2 -Ieth0 "$addr" || continue
+            ip a add "$inet" brd + dev eth0
+            ip r add default via "$gw" dev eth0
+            echo -e "nameserver $gw" >> /etc/resolv.conf
+            break
+        done < /boot/eth.nodhcp
 
-                arping -Dqc2 -Ieth0 $addr || continue
-                ip a add $inet brd + dev eth0
-                ip r add default via $gw dev eth0
-                cp -f /etc/resolv.conf /etc/resolv.conf.old
-                cat > /etc/resolv.conf << EOF
-nameserver $gw
-nameserver 8.8.4.4
-nameserver 8.8.8.8
-nameserver 114.114.114.114
-nameserver 119.29.29.29
-nameserver 223.5.5.5
-EOF
-                break
-            done &&
-            ip a show dev eth0|grep inet || (
-                udhcpc -i eth0 -t 3 -T 1 -A 5 -b -p /run/udhcpc.eth0.pid &>/dev/null
-                ip a show dev eth0|grep inet
-            ) || (
-                # failed to apply dynamic addr, need a available static addr to visit the LAN 
-                inet=$RESERVE_INET
-                addr=${inet%/*}
-                ip a add $inet brd + dev eth0
-            ) || exit 1
+        ip a show dev eth0 | grep inet > /dev/null || {
+            udhcpc -i eth0 -t 3 -T 1 -A 5 -b -p /run/udhcpc.eth0.pid &>/dev/null
+            ip a show dev eth0 | grep inet > /dev/null
+        } || {
+            inet=$RESERVE_INET
+            addr=${inet%/*}
+            ip a add "$inet" brd + dev eth0
+        } || exit 1
     else
-        (udhcpc -i eth0 -t 10 -T 1 -A 5 -b -p /run/udhcpc.eth0.pid) &
+        udhcpc -i eth0 -t 10 -T 1 -A 5 -b -p /run/udhcpc.eth0.pid &
     fi
-
-    echo "OK"
 }
+
 stop() {
-    [[ ! -e "/run/udhcpc.eth0.pid" ]] && echo "udhcpc is not running..." && exit 1
-    kill `cat /run/udhcpc.eth0.pid`
+    [ ! -e "/run/udhcpc.eth0.pid" ] && exit 1
+    kill "$(cat /run/udhcpc.eth0.pid)"
     rm /run/udhcpc.eth0.pid
 }
 
 case "$1" in
-        start)
-                start
-                ;;
-        stop)
-                stop
-                ;;
-        restart|reload)
-                $0 stop
-                $0 start
-                ;;
-        doc)
-                cat <<EOF
-If you want to set your own static ip address
-    rather then fetch it by dhcp.
-Then you need to create a file \`/boot/eth.nodhcp\`,
-    and edit it following the format below:
-    \`addr/netid        gw[optional]\` in one line
-    for example (support muti definations, checks with arp):
-    1. 192.168.0.101/24 192.168.0.1
-    2. 192.168.3.116/22
-Delete this file if you change to use dhcp default.
-ATTENTION: If all the STATIC address you set in the file is
-    already in use on this LAN checked with arp, then none
-    of them will be yours. And it will trigger dhcp, try to 
-    fetch DYNAMIC one. If it's also failed, your address will 
-    be the REVERSE one, 192.168.0.1/24. Just to be sure that
-    you can visit your NanoKVM device through eth to fix some
-    problems by ssh, unless you must disassemble it and modify
-    or rewrite the TFCard once again.
-EOF
-                echo ""
-                cat <<EOF
-如果您想自行设置静态 ip 地址而不是使用 dhcp 来获取它。
-
-那么您需要新建一个文件 \`/boot/eth.nodhcp\`，然后按照以下格式编辑它：
-    \`addr/netid        gw[optional]\` 在一行内
-示例（支持多个预设，会通过 arp 检查是否占用）：
-    1. 192.168.0.101/24 192.168.0.1
-    2. 192.168.3.116/22
-
-如果您想改回默认 dhcp 获取 ip 地址的方式，删除该文件后即可恢复。
-
-注意：如果您预设的所有静态 ip 地址都被 arp 检测到已占用，则不会成功设置。
-    此时会触发 dhcp 尝试获取 ip 地址，如果仍失败，那么最终会强制设置成
-    192.168.90.1/24。这是为了保证您的 NanoKVM 设备总是能有一个可用的
-    ip 地址，方便您通过局域网 ssh 连接设备进行一些修复，否则您可能需要
-    拆开外壳以手动修改 TF 卡或重新烧卡。
-
-
-EOF
-                ;;
-        *)
-                echo "Usage: $0 {start|stop|restart}"
-                exit 1
-esac
+    start) start ;;
+    stop) stop ;;
+    restart|reload)
+        $0 stop
+        $0 start
+        ;;
+    *) exit 1 ;;
+esac
\ No newline at end of file