diff --git a/README.md b/README.md
index beb4dd6..c866a80 100644
--- a/README.md
+++ b/README.md
@@ -3,13 +3,11 @@
 ## Step 1. Preparation
 
  - A clean normally running true virtualization (e.g. KVM) VPS with GRUB2 and VNC access. This script have been tested on SolusVM KVM VPS & Alibaba Cloud ECS with Debian 8/9 & Ubuntu 16.04/18.04.
-
  - Then check `/etc/default/grub` with your preferred editor (e.g. `nano` or `vi`).
-
+ - Set `GRUB_DEFAULT` to `2` (which means select 3rd entry by default) will let **most of** virtual instances boot to installer automatically after timeout.
+ - Make sure there's reasonable number for `GRUB_TIMEOUT` **timeout**. You can just set `GRUB_TIMEOUT=30` which will be fine.
  - Make sure there's **no** `GRUB_HIDDEN_TIMEOUT_QUIET` and `GRUB_HIDDEN_TIMEOUT`. **Just delete them.**
 
- - Make sure there's reasonable number for `GRUB_TIMEOUT` **timeout**. You can just set `GRUB_TIMEOUT=600` which will be fine (it's 10 minutes).
-
 Install dependencies:
 
 ```
@@ -29,7 +27,7 @@ sudo sh -c "$(wget -O - https://github.com/brentybh/debian-netboot/raw/master/ne
 ### All Options
 
  - `-c US` Debian Installer Country
- - `-fqdn unassigned-hostname.unassigned-domain` FQDN including hostname and domain
+ - `-fqdn debian` FQDN including hostname and domain
  - `-proto http` Transport protocol for archive mirror only but not security repository (`http`, `https`, `ftp`)
  - `-host deb.debian.org` Host for archive mirror only but not security repository
  - `-dir /debian` Directory path relative to root of the mirror
@@ -41,18 +39,20 @@ sudo sh -c "$(wget -O - https://github.com/brentybh/debian-netboot/raw/master/ne
  - `-upgrade full-upgrade` Whether to upgrade packages after debootstrap (`none`, `safe-upgrade`, `full-upgrade`)
  - `-s http://security.debian.org/debian-security` Custom URL for security repository mirror
  - `-ip 192.168.1.42` Configure network manually with an IP address (following options only work when IP address specified)
+ - `-fs ext4` Filesystem for partition
  - `-cidr 255.255.255.0` Netmask for manual network configuration
  - `-gw 192.168.1.1` Gateway for manual network configuration
  - `-ns "8.8.8.8 8.8.4.4"` DNS for manual network configuration
  - `-add "ca-certificates curl fail2ban openssl whois"` Include individual additional packages to install
  - `-ssh secret` Enable network console and specify **password for SSH access during install process**. You can login with `installer` user and check system logs.
+ - `-dry-run` Generate `preseed.cfg` and save to current dir but don't actually do anything
 
 ### Chinese Special
 
 If `-c CN` is used, Chinese Special options will be setup for good connectivity and experience against GFW.
 
- - Default archive mirror is `https://mirrors.ustc.edu.cn/debian`.
- - Default security mirror is `https://mirrors.ustc.edu.cn/debian-security`.
+ - Default archive mirror is `https://chinanet.mirrors.ustc.edu.cn/debian`.
+ - Default security mirror is `https://chinanet.mirrors.ustc.edu.cn/debian-security`.
  - Default time zone is `Asia/Shanghai`.
  - Default NTP server is `cn.ntp.org.cn`.
  - Default DNS is `156.154.70.5 156.154.71.5`.
@@ -63,5 +63,6 @@ If `-c CN` is used, Chinese Special options will be setup for good connectivity
  - Keep your SSH connection and **open VNC console** on your Provider's control panel.
  - `sudo reboot` with your SSH and the VM should **reboot**.
  - Switch to your VNC window **quickly**. You should enter the **GRUB selection menu** now.
- - Use your keyboard to **select** `New Install` and **enter** it. Also, **be quick**, just do not miss the `GRUB_TIMEOUT` timeout you've set.
+ - If you've configured correct `GRUB_DEFAULT`, it should be booted into installer automatically after timeout.
+ - Or, use your keyboard to **select** `New Install` and **enter** it. Also, **be quick**, just do not miss the `GRUB_TIMEOUT` timeout you've set.
  - Finally, you should see the screen of Debian Installer now. It will setup all things automatically and reboot when complete.
diff --git a/netboot.sh b/netboot.sh
index 492cf84..07036dd 100644
--- a/netboot.sh
+++ b/netboot.sh
@@ -92,6 +92,13 @@ while [ $# -gt 0 ]; do
       SSH_PASSWD=$2
       shift
       ;;
+    -fs)
+      FILESYS=$2
+      shift
+      ;;
+    -dry-run)
+      DRYRUN=true
+    ;;
     *)
       echo "Illegal option $1"
       exit 1
@@ -102,7 +109,7 @@ done
 case "$COUNTRY" in
   CN)
     PROTO=${PROTO:-https}
-    HOST=${HOST:-mirrors.ustc.edu.cn}
+    HOST=${HOST:-chinanet.mirrors.ustc.edu.cn}
     TIME_ZONE=${TIME_ZONE:-Asia/Shanghai}
     NTP=${NTP:-cn.ntp.org.cn}
     SECURITY=${SECURITY:-true}
@@ -120,6 +127,7 @@ TIME_ZONE=${TIME_ZONE:-UTC}
 NTP=${NTP:-pool.ntp.org}
 UPGRADE=${UPGRADE:-full-upgrade}
 DNS=${DNS:-8.8.8.8 8.8.4.4}
+FILESYS=${FILESYS:-ext4}
 
 if [ -z "$SECURITY" ]; then
   SECURITY=http://security.debian.org/debian-security
@@ -135,6 +143,9 @@ else
   PASSWD=$(mkpasswd -m sha-512 "$PASSWD")
 fi
 
+
+if [ "$DRYRUN" != true ]; then
+
 BOOT=/boot/debian-$SUITE
 URL=$PROTO://$HOST$DIR/dists/$SUITE/main/installer-$ARCH/current/images/netboot/debian-installer/$ARCH
 
@@ -143,6 +154,8 @@ rm -fr "$BOOT"
 mkdir -p "$BOOT"
 cd "$BOOT"
 
+fi
+
 cat >> preseed.cfg << EOF
 # COUNTRY: 1
 # IP_ADDR: 2
@@ -159,6 +172,7 @@ cat >> preseed.cfg << EOF
 # PASSWD: 4
 # TIME_ZONE: 5
 # NTP: 5
+# FILESYS: 6
 # SECURITY: 8
 # INCLUDE: 9
 # UPGRADE: 9
@@ -192,8 +206,8 @@ if [ -n "$IP_ADDR" ]; then
 fi
 
 cat >> preseed.cfg << EOF
-d-i netcfg/get_hostname string unassigned-hostname
-d-i netcfg/get_domain string unassigned-domain
+d-i netcfg/get_hostname string debian
+d-i netcfg/get_domain string
 EOF
 
 if [ -n "$FQDN" ]; then
@@ -238,7 +252,7 @@ d-i time/zone string {{-TIME_ZONE-}}
 d-i clock-setup/ntp boolean true
 d-i clock-setup/ntp-server string {{-NTP-}}
 
-# 6. Partitioning
+# 6. Partitioning: FILESYS
 
 d-i partman-basicfilesystems/no_swap boolean false
 d-i partman-auto/method string regular
@@ -246,7 +260,7 @@ d-i partman-lvm/device_remove_lvm boolean true
 d-i partman-md/device_remove_md boolean true
 d-i partman-lvm/confirm boolean true
 d-i partman-lvm/confirm_nooverwrite boolean true
-d-i partman-auto/expert_recipe string naive :: 0 1 -1 ext4 $primary{ } $bootable{ } method{ format } format{ } use_filesystem{ } filesystem{ ext4 } mountpoint{ / } .
+d-i partman-auto/expert_recipe string naive :: 0 1 -1 {{-FILESYS-}} $primary{ } $bootable{ } method{ format } format{ } use_filesystem{ } filesystem{ {{-FILESYS-}} } mountpoint{ / } .
 d-i partman-auto/choose_recipe select naive
 d-i partman-partitioning/confirm_write_new_label boolean true
 d-i partman/choose_partition select finish
@@ -298,6 +312,9 @@ sed -i 's/{{-TIME_ZONE-}}/'$(echo "$TIME_ZONE" | sed 's/\//\\\//g')'/g' preseed.
 sed -i 's/{{-NTP-}}/'"$NTP"'/g' preseed.cfg
 sed -i 's/{{-SECURITY-}}/'$(echo "$SECURITY" | sed 's/\//\\\//g')'/g' preseed.cfg
 sed -i 's/{{-UPGRADE-}}/'"$UPGRADE"'/g' preseed.cfg
+sed -i 's/{{-FILESYS-}}/'"$FILESYS"'/g' preseed.cfg
+
+if [ "$DRYRUN" != true ]; then
 
 wget "$URL/linux" "$URL/initrd.gz"
 gunzip initrd.gz
@@ -313,3 +330,5 @@ linux $BOOT/linux
 initrd $BOOT/initrd.gz
 }
 EOF
+
+fi