diff --git a/README.md b/README.md
index 90a64ee..c6362ed 100644
--- a/README.md
+++ b/README.md
@@ -270,6 +270,7 @@ You don't have to do anything manually!
 1. ISPConfig 3.1 API
 1. Alwaysdata.com API
 1. Linode.com API
+1. FreeDNS (https://freedns.afraid.org/)
 
 **More APIs coming soon...**
 
diff --git a/acme.sh b/acme.sh
index bc21152..df4a0b4 100755
--- a/acme.sh
+++ b/acme.sh
@@ -340,11 +340,29 @@ _is_solaris() {
   _contains "${__OS__:=$(uname -a)}" "solaris" || _contains "${__OS__:=$(uname -a)}" "SunOS"
 }
 
+#_ascii_hex str
+#this can only process ascii chars, should only be used when od command is missing as a backup way.
+_ascii_hex() {
+  _debug2 "Using _ascii_hex"
+  _str="$1"
+  _str_len=${#_str}
+  _h_i=1
+  while [ "$_h_i" -le "$_str_len" ]; do
+    _str_c="$(printf "%s" "$_str" | cut -c "$_h_i")"
+    printf " %02x" "'$_str_c"
+    _h_i="$(_math "$_h_i" + 1)"
+  done
+}
+
 #stdin  output hexstr splited by one space
 #input:"abc"
 #output: " 61 62 63"
 _hex_dump() {
-  od -A n -v -t x1 | tr -d "\r\t" | tr -s " " | sed "s/ $//" | tr -d "\n"
+  #in wired some system, the od command is missing.
+  if ! od -A n -v -t x1 | tr -d "\r\t" | tr -s " " | sed "s/ $//" | tr -d "\n" 2>/dev/null; then
+    str=$(cat)
+    _ascii_hex "$str"
+  fi
 }
 
 #url encode, no-preserved chars
diff --git a/dnsapi/README.md b/dnsapi/README.md
index df728ac..6a86bf4 100644
--- a/dnsapi/README.md
+++ b/dnsapi/README.md
@@ -278,6 +278,33 @@ acme.sh --issue --dns dns_linode --dnssleep 900 -d example.com -d www.example.co
 
 The `LINODE_API_KEY` will be saved in `~/.acme.sh/account.conf` and will be reused when needed.
 
+## 15. Use FreeDNS
+
+FreeDNS (https://freedns.afraid.org/) does not provide an API to update DNS records (other than IPv4 and IPv6
+dynamic DNS addresses).  The acme.sh plugin therefore retrieves and updates domain TXT records by logging
+into the FreeDNS website to read the HTML and posting updates as HTTP.  The plugin needs to know your
+userid and password for the FreeDNS website.
+
+```sh
+export FREEDNS_User="..."
+export FREEDNS_Password="..."
+```
+
+You need only provide this the first time you run the acme.sh client with FreeDNS validation and then again
+whenever you change your password at the FreeDNS site.  The acme.sh FreeDNS plugin does not store your userid
+or password but rather saves an authentication token returned by FreeDNS in `~/.acme.sh/account.conf` and
+reuses that when needed.
+
+Now you can issue a certificate.
+
+```sh
+acme.sh --issue --dns dns_freedns -d example.com -d www.example.com
+```
+
+Note that you cannot use acme.sh automatic DNS validation for FreeDNS public domains or for a subdomain that
+you create under a FreeDNS public domain.  You must own the top level domain in order to automaitcally
+validate with acme.sh at FreeDNS.
+
 # Use custom API
 
 If your API is not supported yet, you can write your own DNS API.
diff --git a/dnsapi/dns_freedns.sh b/dnsapi/dns_freedns.sh
new file mode 100755
index 0000000..f30c895
--- /dev/null
+++ b/dnsapi/dns_freedns.sh
@@ -0,0 +1,375 @@
+#!/usr/bin/env sh
+
+#This file name is "dns_freedns.sh"
+#So, here must be a method dns_freedns_add()
+#Which will be called by acme.sh to add the txt record to your api system.
+#returns 0 means success, otherwise error.
+#
+#Author: David Kerr
+#Report Bugs here: https://github.com/dkerr64/acme.sh
+#
+########  Public functions #####################
+
+# Export FreeDNS userid and password in folowing variables...
+#  FREEDNS_User=username
+#  FREEDNS_Password=password
+# login cookie is saved in acme account config file so userid / pw
+# need to be set only when changed.
+
+#Usage: dns_freedns_add   _acme-challenge.www.domain.com   "XKrxpRBosdIKFzxW_CT3KLZNf6q0HG9i01zxXp5CPBs"
+dns_freedns_add() {
+  fulldomain="$1"
+  txtvalue="$2"
+
+  _info "Add TXT record using FreeDNS"
+  _debug "fulldomain: $fulldomain"
+  _debug "txtvalue: $txtvalue"
+
+  if [ -z "$FREEDNS_User" ] || [ -z "$FREEDNS_Password" ]; then
+    FREEDNS_User=""
+    FREEDNS_Password=""
+    if [ -z "$FREEDNS_COOKIE" ]; then
+      _err "You did not specify the FreeDNS username and password yet."
+      _err "Please export as FREEDNS_User / FREEDNS_Password and try again."
+      return 1
+    fi
+    using_cached_cookies="true"
+  else
+    FREEDNS_COOKIE="$(_freedns_login "$FREEDNS_User" "$FREEDNS_Password")"
+    if [ -z "$FREEDNS_COOKIE" ]; then
+      return 1
+    fi
+    using_cached_cookies="false"
+  fi
+
+  _debug "FreeDNS login cookies: $FREEDNS_COOKIE (cached = $using_cached_cookies)"
+
+  _saveaccountconf FREEDNS_COOKIE "$FREEDNS_COOKIE"
+
+  # split our full domain name into two parts...
+  i="$(echo "$fulldomain" | tr '.' ' ' | wc -w)"
+  i="$(_math "$i" - 1)"
+  top_domain="$(echo "$fulldomain" | cut -d. -f "$i"-100)"
+  i="$(_math "$i" - 1)"
+  sub_domain="$(echo "$fulldomain" | cut -d. -f -"$i")"
+
+  # Sometimes FreeDNS does not reurn the subdomain page but rather 
+  # returns a page regarding becoming a premium member.  This usually
+  # happens after a period of inactivity.  Immediately trying again
+  # returns the correct subdomain page.  So, we will try twice to
+  # load the page and obtain our domain ID
+  attempts=2
+  while [ "$attempts" -gt "0" ]; do
+    attempts="$(_math "$attempts" - 1)"
+
+    htmlpage="$(_freedns_retrieve_subdomain_page "$FREEDNS_COOKIE")"
+    if [ "$?" != "0" ]; then
+      if [ "$using_cached_cookies" = "true" ]; then
+        _err "Has your FreeDNS username and password channged?  If so..."
+        _err "Please export as FREEDNS_User / FREEDNS_Password and try again."
+      fi
+      return 1
+    fi
+
+    # Now convert the tables in the HTML to CSV.  This litte gem from
+    # http://stackoverflow.com/questions/1403087/how-can-i-convert-an-html-table-to-csv    
+    subdomain_csv="$(echo "$htmlpage" \
+      | grep -i -e '</\?TABLE\|</\?TD\|</\?TR\|</\?TH' \
+      | sed 's/^[\ \t]*//g' \
+      | tr -d '\n' \
+      | sed 's/<\/TR[^>]*>/\n/Ig' \
+      | sed 's/<\/\?\(TABLE\|TR\)[^>]*>//Ig' \
+      | sed 's/^<T[DH][^>]*>\|<\/\?T[DH][^>]*>$//Ig' \
+      | sed 's/<\/T[DH][^>]*><T[DH][^>]*>/,/Ig' \
+      | grep 'edit.php?' \
+      | grep "$top_domain")"
+    # The above beauty ends with striping out rows that do not have an
+    # href to edit.php and do not have the top domain we are looking for.
+    # So all we should be left with is CSV of table of subdomains we are
+    # interested in.
+
+    # Now we have to read through this table and extract the data we need
+    lines="$(echo "$subdomain_csv" | wc -l)"
+    nl='
+'
+    i=0
+    found=0
+    while [ "$i" -lt "$lines" ]; do
+      i="$(_math "$i" + 1)"
+      line="$(echo "$subdomain_csv" | cut -d "$nl" -f "$i")"
+      tmp="$(echo "$line" | cut -d ',' -f 1)"
+      if [ $found = 0 ] && _startswith "$tmp" "<td>$top_domain"; then
+        # this line will contain DNSdomainid for the top_domain
+        DNSdomainid="$(echo "$line" | cut -d ',' -f 2 | sed 's/^.*domain_id=//;s/>.*//')"
+        found=1
+      else
+        # lines contain DNS records for all subdomains
+        DNSname="$(echo "$line" | cut -d ',' -f 2 | sed 's/^[^>]*>//;s/<\/a>.*//')"
+        DNStype="$(echo "$line" | cut -d ',' -f 3)"
+        if [ "$DNSname" = "$fulldomain" ] && [ "$DNStype" = "TXT" ]; then
+          DNSdataid="$(echo "$line" | cut -d ',' -f 2 | sed 's/^.*data_id=//;s/>.*//')"
+          # Now get current value for the TXT record.  This method may
+          # not produce accurate results as the value field is truncated
+          # on this webpage. To get full value we would need to load
+          # another page. However we don't really need this so long as
+          # there is only one TXT record for the acme chalenge subdomain.
+          DNSvalue="$(echo "$line" | cut -d ',' -f 4 | sed 's/^[^&quot;]*&quot;//;s/&quot;.*//;s/<\/td>.*//')"
+          if [ $found != 0 ]; then
+            break
+            # we are breaking out of the loop at the first match of DNS name
+            # and DNS type (if we are past finding the domainid). This assumes
+            # that there is only ever one TXT record for the LetsEncrypt/acme
+            # challenge subdomain.  This seems to be a reasonable assumption
+            # as the acme client deletes the TXT record on successful validation.
+          fi
+        else
+          DNSname=""
+          DNStype=""
+        fi
+      fi
+    done
+
+    _debug "DNSname: $DNSname DNStype: $DNStype DNSdomainid: $DNSdomainid DNSdataid: $DNSdataid"
+    _debug "DNSvalue: $DNSvalue"
+
+    if [ -z "$DNSdomainid" ]; then
+      # If domain ID is empty then something went wrong (top level
+      # domain not found at FreeDNS).
+      if [ "$attempts" = "0" ]; then
+        # exhausted maximum retry attempts
+        _debug "$htmlpage"
+        _debug "$subdomain_csv"
+        _err "Domain $top_domain not found at FreeDNS"
+        return 1
+      fi
+    else
+      # break out of the 'retry' loop... we have found our domain ID
+      break
+    fi
+    _info "Domain $top_domain not found at FreeDNS"
+    _info "Retry loading subdomain page ($attempts attempts remaining)"
+  done
+
+  if [ -z "$DNSdataid" ]; then
+    # If data ID is empty then specific subdomain does not exist yet, need
+    # to create it this should always be the case as the acme client
+    # deletes the entry after domain is validated.
+    _freedns_add_txt_record "$FREEDNS_COOKIE" "$DNSdomainid" "$sub_domain" "$txtvalue"
+    return $?
+  else
+    if [ "$txtvalue" = "$DNSvalue" ]; then
+      # if value in TXT record matches value requested then DNS record
+      # does not need to be updated. But...
+      # Testing value match fails.  Website is truncating the value field.
+      # So for now we will always go down the else path.  Though in theory
+      # should never come here anyway as the acme client deletes
+      # the TXT record on successful validation, so we should not even
+      # have found a TXT record !!
+      _info "No update necessary for $fulldomain at FreeDNS"
+      return 0
+    else
+      # Delete the old TXT record (with the wrong value)
+      _freedns_delete_txt_record "$FREEDNS_COOKIE" "$DNSdataid"
+      if [ "$?" = "0" ]; then
+        # And add in new TXT record with the value provided
+        _freedns_add_txt_record "$FREEDNS_COOKIE" "$DNSdomainid" "$sub_domain" "$txtvalue"
+      fi
+      return $?
+    fi
+  fi
+  return 0
+}
+
+#Usage: fulldomain txtvalue
+#Remove the txt record after validation.
+dns_freedns_rm() {
+  fulldomain="$1"
+  txtvalue="$2"
+
+  _info "Delete TXT record using FreeDNS"
+  _debug "fulldomain: $fulldomain"
+  _debug "txtvalue: $txtvalue"
+
+  # Need to read cookie from conf file again in case new value set
+  # during login to FreeDNS when TXT record was created.
+  # acme.sh does not have a _readaccountconf() fuction
+  FREEDNS_COOKIE="$(_read_conf "$ACCOUNT_CONF_PATH" "FREEDNS_COOKIE")"
+  _debug "FreeDNS login cookies: $FREEDNS_COOKIE"
+
+  # Sometimes FreeDNS does not reurn the subdomain page but rather 
+  # returns a page regarding becoming a premium member.  This usually
+  # happens after a period of inactivity.  Immediately trying again
+  # returns the correct subdomain page.  So, we will try twice to
+  # load the page and obtain our TXT record.
+  attempts=2
+  while [ "$attempts" -gt "0" ]; do
+    attempts="$(_math "$attempts" - 1)"
+
+    htmlpage="$(_freedns_retrieve_subdomain_page "$FREEDNS_COOKIE")"
+    if [ "$?" != "0" ]; then
+      return 1
+    fi
+
+    # Now convert the tables in the HTML to CSV.  This litte gem from
+    # http://stackoverflow.com/questions/1403087/how-can-i-convert-an-html-table-to-csv
+    subdomain_csv="$(echo "$htmlpage" \
+      | grep -i -e '</\?TABLE\|</\?TD\|</\?TR\|</\?TH' \
+      | sed 's/^[\ \t]*//g' \
+      | tr -d '\n' \
+      | sed 's/<\/TR[^>]*>/\n/Ig' \
+      | sed 's/<\/\?\(TABLE\|TR\)[^>]*>//Ig' \
+      | sed 's/^<T[DH][^>]*>\|<\/\?T[DH][^>]*>$//Ig' \
+      | sed 's/<\/T[DH][^>]*><T[DH][^>]*>/,/Ig' \
+      | grep 'edit.php?' \
+      | grep "$fulldomain")"
+    # The above beauty ends with striping out rows that do not have an
+    # href to edit.php and do not have the domain name we are looking for.
+    # So all we should be left with is CSV of table of subdomains we are
+    # interested in.
+
+    # Now we have to read through this table and extract the data we need
+    lines="$(echo "$subdomain_csv" | wc -l)"
+    nl='
+'
+    i=0
+    found=0
+    while [ "$i" -lt "$lines" ]; do
+      i="$(_math "$i" + 1)"
+      line="$(echo "$subdomain_csv" | cut -d "$nl" -f "$i")"
+      DNSname="$(echo "$line" | cut -d ',' -f 2 | sed 's/^[^>]*>//;s/<\/a>.*//')"
+      DNStype="$(echo "$line" | cut -d ',' -f 3)"
+      if [ "$DNSname" = "$fulldomain" ] && [ "$DNStype" = "TXT" ]; then
+        DNSdataid="$(echo "$line" | cut -d ',' -f 2 | sed 's/^.*data_id=//;s/>.*//')"
+        DNSvalue="$(echo "$line" | cut -d ',' -f 4 | sed 's/^[^&quot;]*&quot;//;s/&quot;.*//;s/<\/td>.*//')"
+        _debug "DNSvalue: $DNSvalue"
+        #     if [ "$DNSvalue" = "$txtvalue" ]; then
+        # Testing value match fails.  Website is truncating the value
+        # field. So for now we will assume that there is only one TXT
+        # field for the sub domain and just delete it. Currently this
+        # is a safe assumption.
+        _freedns_delete_txt_record "$FREEDNS_COOKIE" "$DNSdataid"
+        return $?
+        #     fi
+      fi
+    done
+  done
+
+  # If we get this far we did not find a match (after two attempts)
+  # Not necessarily an error, but log anyway.
+  _debug2 "$subdomain_csv"
+  _info "Cannot delete TXT record for $fulldomain/$txtvalue. Does not exist at FreeDNS"
+  return 0
+}
+
+####################  Private functions below ##################################
+
+# usage: _freedns_login username password
+# print string "cookie=value" etc.
+# returns 0 success
+_freedns_login() {
+  export _H1="Accept-Language:en-US"
+  username="$1"
+  password="$2"
+  url="https://freedns.afraid.org/zc.php?step=2"
+
+  _debug "Login to FreeDNS as user $username"
+
+  htmlpage="$(_post "username=$(printf '%s' "$username" | _url_encode)&password=$(printf '%s' "$password" | _url_encode)&submit=Login&action=auth" "$url")"
+
+  if [ "$?" != "0" ]; then
+    _err "FreeDNS login failed for user $username bad RC from _post"
+    return 1
+  fi
+
+  cookies="$(grep -i '^Set-Cookie.*dns_cookie.*$' "$HTTP_HEADER" | _head_n 1 | tr -d "\r\n" | cut -d " " -f 2)"
+
+  # if cookies is not empty then logon successful
+  if [ -z "$cookies" ]; then
+    _debug "$htmlpage"
+    _err "FreeDNS login failed for user $username. Check $HTTP_HEADER file"
+    return 1
+  fi
+
+  printf "%s" "$cookies"
+  return 0
+}
+
+# usage _freedns_retrieve_subdomain_page login_cookies
+# echo page retrieved (html)
+# returns 0 success
+_freedns_retrieve_subdomain_page() {
+  export _H1="Cookie:$1"
+  export _H2="Accept-Language:en-US"
+  url="https://freedns.afraid.org/subdomain/"
+
+  _debug "Retrieve subdmoain page from FreeDNS"
+
+  htmlpage="$(_get "$url")"
+
+  if [ "$?" != "0" ]; then
+    _err "FreeDNS retrieve subdomins failed bad RC from _get"
+    return 1
+  elif [ -z "$htmlpage" ]; then
+    _err "FreeDNS returned empty subdomain page"
+    return 1
+  fi
+
+  _debug2 "$htmlpage"
+
+  printf "%s" "$htmlpage"
+  return 0
+}
+
+# usage _freedns_add_txt_record login_cookies domain_id subdomain value
+# returns 0 success
+_freedns_add_txt_record() {
+  export _H1="Cookie:$1"
+  export _H2="Accept-Language:en-US"
+  domain_id="$2"
+  subdomain="$3"
+  value="$(printf '%s' "$4" | _url_encode)"
+  url="http://freedns.afraid.org/subdomain/save.php?step=2"
+
+  htmlpage="$(_post "type=TXT&domain_id=$domain_id&subdomain=$subdomain&address=%22$value%22&send=Save%21" "$url")"
+
+  if [ "$?" != "0" ]; then
+    _err "FreeDNS failed to add TXT record for $subdomain bad RC from _post"
+    return 1
+  elif ! grep "200 OK" "$HTTP_HEADER" >/dev/null; then
+    _debug "$htmlpage"
+    _err "FreeDNS failed to add TXT record for $subdomain. Check $HTTP_HEADER file"
+    return 1
+  elif _contains "$htmlpage" "security code was incorrect"; then
+    _debug "$htmlpage"
+    _err "FreeDNS failed to add TXT record for $subdomain as FreeDNS requested seurity code"
+    _err "Note that you cannot use automatic DNS validation for FreeDNS public domains"
+    return 1
+  fi
+
+  _debug2 "$htmlpage"
+  _info "Added acme challenge TXT record for $fulldomain at FreeDNS"
+  return 0
+}
+
+# usage _freedns_delete_txt_record login_cookies data_id
+# returns 0 success
+_freedns_delete_txt_record() {
+  export _H1="Cookie:$1"
+  export _H2="Accept-Language:en-US"
+  data_id="$2"
+  url="https://freedns.afraid.org/subdomain/delete2.php"
+
+  htmlheader="$(_get "$url?data_id%5B%5D=$data_id&submit=delete+selected" "onlyheader")"
+
+  if [ "$?" != "0" ]; then
+    _err "FreeDNS failed to delete TXT record for $data_id bad RC from _get"
+    return 1
+  elif ! _contains "$htmlheader" "200 OK"; then
+    _debug "$htmlheader"
+    _err "FreeDNS failed to delete TXT record $data_id"
+    return 1
+  fi
+
+  _info "Deleted acme challenge TXT record for $fulldomain at FreeDNS"
+  return 0
+}