diff --git a/git-recursive.sh b/git-recursive.sh
new file mode 100755
index 0000000..ff6ff6d
--- /dev/null
+++ b/git-recursive.sh
@@ -0,0 +1,157 @@
+#!/bin/bash
+if [[ -z "$TUNASYNC_UPSTREAM_URL" ]];then
+  echo "Please set the TUNASYNC_UPSTREAM_URL"
+  exit 1
+fi
+
+if [[ ! -z "$RECURSIVE" ]];then
+  echo "Sync in a recursive mode"
+fi
+
+TMPDIR=${TMPDIR:-"/tmp"}
+
+MIRROR_BASE_URL=${MIRROR_BASE_URL:-"https://mirrors.tuna.tsinghua.edu.cn/git/"}
+WORKING_DIR_BASE=${WORKING_DIR_BASE:-"/data/mirrors/git/"}
+GENERATED_SCRIPT=${GENERATED_SCRIPT:-"/data/mirrors/git/qemu/qemu.sh"}
+
+if [[ ! -z "$RECURSIVE" ]]; then
+  echo "#!/usr/bin/env bash" > $GENERATED_SCRIPT.tmp
+fi
+
+function script_append() {
+if [[ ! -z "$RECURSIVE" ]]; then
+  echo "$1" >> $GENERATED_SCRIPT.tmp
+fi
+}
+
+depth=0
+
+function echon() {
+  echo depth $depth $@
+}
+
+function repo_init() {
+  local upstream=$1
+  local working_dir=$2
+  git clone --mirror "$upstream" "$working_dir"
+}
+
+function update_linux_git() {
+  local upstream=$1
+  local working_dir=$2
+  cd "$working_dir"
+  echon "==== SYNC $upstream START ===="
+  git remote set-url origin "$upstream"
+  /usr/bin/timeout -s INT 3600 git remote -v update -p
+  local ret=$?
+  [[ $ret -ne 0 ]] && echon "git update failed with rc=$ret"
+  local head=$(git remote show origin | awk '/HEAD branch:/ {print $NF}')
+  [[ -n "$head" ]] && echo "ref: refs/heads/$head" > HEAD
+  objs=$(find objects -type f | wc -l)
+  [[ "$objs" -gt 8 ]] && git repack -a -b -d
+  sz=$(git count-objects -v|grep -Po '(?<=size-pack: )\d+')
+  total_size=$(($total_size+1024*$sz))
+  echon "==== SYNC $upstream DONE ===="
+  return $ret
+}
+
+function git_sync() {
+  local upstream=$1
+  local working_dir=$2
+  if [[ ! -f "$working_dir/HEAD" ]]; then
+    echon "Initializing $upstream mirror"
+    repo_init $1 $2
+    return $?
+  fi
+  update_linux_git $1 $2
+}
+
+function checkout_repo() {
+  local repo_dir="$1"
+  local work_tree="$2"
+  local commit="$3"
+  echon "Checkout $repo_dir to $work_tree"
+  rm -rf $work_tree
+  git clone "$repo_dir" "$work_tree"
+  local ret=$?
+  if [[ $ret -ne 0 ]]; then
+    echon "git clone failed with rc=$ret"
+    return $ret
+  fi
+  if [[ ! -z "$commit" ]]; then
+    echon "Worktree $work_tree switch to commit $commit"
+    git -C $work_tree checkout $commit
+  fi
+
+  local repo_dir_no_git=${repo_dir%%.git}
+  local gitmodules="$work_tree/.gitmodules"
+  if [[ -f "$gitmodules" ]]; then
+    local paths_str=$(cat $gitmodules | grep path | cut -d '=' -f 2 | sed 's/^[[:blank:]]*//')
+    local urls_str=$(cat $gitmodules | grep url | cut -d '=' -f 2 | sed 's/^[[:blank:]]*//')
+    local -a paths
+    local -a urls
+    readarray -t paths <<<"$paths_str"
+    readarray -t urls <<<"$urls_str"
+    local -i i
+    for ((i=0;i<${#paths[@]};i++)); do
+      local path=${paths[$i]}
+      # ignore empty .gitmodules
+      if [[ "$path" == "" ]]; then
+        continue
+      fi
+      local commit=$(git -C $work_tree submodule status $path | cut -d ' ' -f 1 | cut -d '-' -f 2)
+      local git_path=$repo_dir_no_git/$path.git
+      mkdir -p $git_path
+      local mirror_url=$(echo $git_path | sed "s#$WORKING_DIR_BASE#$MIRROR_BASE_URL#")
+      script_append "cat >>.git/config <<EOF"
+      script_append "[submodule \"$path\"]"
+      script_append "	active = true"
+      script_append "	url = $mirror_url"
+      script_append "EOF"
+      script_append "mkdir -p $path"
+      script_append "git clone $mirror_url $path"
+      script_append "git submodule init $path"
+      script_append "git submodule update $path"
+      script_append "pushd $path"
+      git_sync_recursive ${urls[$i]} $git_path $commit
+      script_append "popd"
+    done
+  fi
+}
+
+function git_sync_recursive() {
+  depth=$(($depth+1))
+  local upstream=$1
+  local working_dir=$2
+  # it is ok that commit=""
+  local commit=$3
+  git_sync $1 $2
+  local ret=$?
+  if [[ $ret -ne 0 ]]; then
+    echon "git sync failed with rc=$ret"
+    return $ret
+  fi
+
+  if [[ ! -z "$RECURSIVE" ]]; then
+    working_dir_name=$(basename $2)
+    working_dir_name_no_git=${working_dir_name%%.git}
+    checkout_repo $working_dir $TMPDIR/$working_dir_name_no_git $commit
+  fi
+  depth=$(($depth-1))
+}
+
+path=$(basename $TUNASYNC_WORKING_DIR)
+path_no_git=${path%%.git}
+mirror_url=$(echo $TUNASYNC_WORKING_DIR | sed "s#$WORKING_DIR_BASE#$MIRROR_BASE_URL#")
+script_append "mkdir -p $path_no_git"
+script_append "git clone $mirror_url $path_no_git"
+script_append "pushd $path_no_git"
+git_sync_recursive $TUNASYNC_UPSTREAM_URL $TUNASYNC_WORKING_DIR
+script_append "git submodule absorbgitdirs"
+script_append "popd"
+
+if [[ ! -z "$RECURSIVE" ]]; then
+  mv $GENERATED_SCRIPT.tmp $GENERATED_SCRIPT
+fi
+
+echo "Total size is" $(numfmt --to=iec $total_size)