diff --git a/shadowsocks-all.sh b/shadowsocks-all.sh
index 0040b77..e4978bb 100644
--- a/shadowsocks-all.sh
+++ b/shadowsocks-all.sh
@@ -34,8 +34,8 @@ software=(Shadowsocks-Python ShadowsocksR Shadowsocks-Go Shadowsocks-libev)
 libsodium_file="libsodium-1.0.13"
 libsodium_url="https://github.com/jedisct1/libsodium/releases/download/1.0.13/libsodium-1.0.13.tar.gz"
 
-mbedtls_file="mbedtls-2.5.1"
-mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.5.1-gpl.tgz"
+mbedtls_file="mbedtls-2.6.0"
+mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.6.0-gpl.tgz"
 
 shadowsocks_python_file="shadowsocks-master"
 shadowsocks_python_url="https://github.com/shadowsocks/shadowsocks/archive/master.zip"
@@ -452,15 +452,15 @@ fi
 install_dependencies() {
     if check_sys packageManager yum; then
         echo -e "[${green}Info${plain}] Adding the EPEL repository..."
-        yum install -y epel-release yum-utils
+        [ ! -f /etc/yum.repos.d/epel.repo ] && yum install -y epel-release yum-utils
         [ ! -f /etc/yum.repos.d/epel.repo ] && echo -e "${red}Error:${plain} Install EPEL repository failed, please check it." && exit 1
-        yum-config-manager --enable epel
+        [ -f /etc/yum.repos.d/epel.repo ] && yum-config-manager --enable epel
         echo -e "[${green}Info${plain}] Adding the EPEL repository complete..."
 
         yum_depends=(
             unzip gzip openssl openssl-devel gcc python python-devel python-setuptools pcre pcre-devel libtool libevent xmlto
             autoconf automake make curl curl-devel zlib-devel perl perl-devel cpio expat-devel gettext-devel asciidoc
-            libev-devel udns-devel
+            libev-devel udns-devel c-ares-devel
         )
         for depend in ${yum_depends[@]}; do
             error_detect_depends "yum -y install ${depend}"
@@ -469,7 +469,7 @@ install_dependencies() {
         apt_depends=(
             gettext build-essential unzip gzip python python-dev python-setuptools curl openssl libssl-dev
             autoconf automake libtool gcc make perl cpio libpcre3 libpcre3-dev zlib1g-dev
-            libudns-dev libev-dev
+            libudns-dev libev-dev libc-ares-dev
         )
         # Check jessie in source.list
         if debianversion 7; then
diff --git a/shadowsocks-libev-debian.sh b/shadowsocks-libev-debian.sh
index d42704c..e2e963b 100644
--- a/shadowsocks-libev-debian.sh
+++ b/shadowsocks-libev-debian.sh
@@ -15,8 +15,8 @@ cur_dir=`pwd`
 libsodium_file="libsodium-1.0.13"
 libsodium_url="https://github.com/jedisct1/libsodium/releases/download/1.0.13/libsodium-1.0.13.tar.gz"
 
-mbedtls_file="mbedtls-2.5.1"
-mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.5.1-gpl.tgz"
+mbedtls_file="mbedtls-2.6.0"
+mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.6.0-gpl.tgz"
 
 # Stream Ciphers
 ciphers=(
@@ -296,7 +296,7 @@ pre_install(){
     # Update System
     apt-get -y update
     # Install necessary dependencies
-    apt-get -y --no-install-recommends install gettext build-essential autoconf automake libtool openssl libssl-dev zlib1g-dev libpcre3-dev libudns-dev libev-dev
+    apt-get -y --no-install-recommends install gettext build-essential autoconf automake libtool openssl libssl-dev zlib1g-dev libpcre3-dev libudns-dev libev-dev libc-ares-dev
 }
 
 download() {
diff --git a/shadowsocks-libev.sh b/shadowsocks-libev.sh
index 6fbec2d..39c818e 100644
--- a/shadowsocks-libev.sh
+++ b/shadowsocks-libev.sh
@@ -15,8 +15,8 @@ cur_dir=`pwd`
 libsodium_file="libsodium-1.0.13"
 libsodium_url="https://github.com/jedisct1/libsodium/releases/download/1.0.13/libsodium-1.0.13.tar.gz"
 
-mbedtls_file="mbedtls-2.5.1"
-mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.5.1-gpl.tgz"
+mbedtls_file="mbedtls-2.6.0"
+mbedtls_url="http://dl.teddysun.com/files/mbedtls-2.6.0-gpl.tgz"
 
 # Stream Ciphers
 ciphers=(
@@ -315,11 +315,11 @@ pre_install(){
     char=`get_char`
     #Install necessary dependencies
     echo -e "[${green}Info${plain}] Adding the EPEL repository..."
-    yum install -y epel-release yum-utils
+    [ ! -f /etc/yum.repos.d/epel.repo ] && yum install -y epel-release yum-utils
     [ ! -f /etc/yum.repos.d/epel.repo ] && echo -e "${red}Error${plain} Install EPEL repository failed, please check it." && exit 1
-    yum-config-manager --enable epel
+    [ -f /etc/yum.repos.d/epel.repo ] && yum-config-manager --enable epel
     echo -e "[${green}Info${plain}] Adding the EPEL repository complete..."
-    yum install -y unzip openssl openssl-devel gettext gcc autoconf libtool automake make asciidoc xmlto udns-devel libev-devel pcre pcre-devel git
+    yum install -y unzip openssl openssl-devel gettext gcc autoconf libtool automake make asciidoc xmlto udns-devel libev-devel pcre pcre-devel git c-ares-devel
 }
 
 download() {