diff --git a/arch/arch_mirror_ranking.py b/arch/arch_mirror_ranking.py
index 98e2758..8f56aa6 100755
--- a/arch/arch_mirror_ranking.py
+++ b/arch/arch_mirror_ranking.py
@@ -139,8 +139,9 @@ def parseArgs():
                            help = ('If specified, only include inactive servers (default is active + inactive)'))
     return(args)
 
+
 if __name__ == '__main__':
     args = vars(parseArgs().parse_args())
     m = MirrorIdx(**args, statuses = True)
     for s in m.ranked_servers:
-        print('Server = {0}$repo/os/$arch'.format(s['url']))
\ No newline at end of file
+        print('Server = {0}$repo/os/$arch'.format(s['url']))
diff --git a/arch/relchk2.py b/arch/relchk2.py
new file mode 100755
index 0000000..8ec78e2
--- /dev/null
+++ b/arch/relchk2.py
@@ -0,0 +1,293 @@
+#!/usr/bin/env python3
+
+import datetime
+import json
+import hashlib
+import os
+import pathlib
+import re
+import shutil
+##
+import psutil
+import requests
+from lxml import etree
+##
+import arch_mirror_ranking  # <optools>/arch/arch_mirror_ranking.py
+
+
+class Updater(object):
+    _fname_re = re.compile(r'^archlinux-(?P<version>[0-9]{4}\.[0-9]{2}\.[0-9]{2})-(?P<arch>(i686|x86_64)).iso$')
+    _def_hash = 'sha1'
+    _allowed_hashes = ('md5', 'sha1')
+    _allowed_arches = ('x86_64', )
+    _date_fmt = '%a, %d %b %Y %H:%M:%S %z'
+    _datever_fmt = '%Y.%m.%d'
+    _arch = 'x86_64'  # Arch Linux proper only offers x86_64.
+    _iso_dir = 'iso/latest'
+    _iso_file = os.path.join(_iso_dir, 'archlinux-{ver}-{arch}.iso')
+
+    def __init__(self,
+                 dest_dir = '/boot/iso',
+                 dest_file = 'arch.iso',
+                 ver_file = '.arch.json',
+                 lock_path = '/tmp/.arch.lck',
+                 feed_url = 'https://archlinux.org/feeds/releases/',
+                 grub_cfg = '/etc/grub.d/40_custom_arch',
+                 # check_gpg = True,  # TODO: GPG sig checking
+                 hash_type = 'sha1'):
+        # if arch.lower() not in self._allowed_arches:
+        #     raise ValueError('arch must be one of: {0}'.format(', '.join(self._allowed_arches)))
+        # else:
+        #     self._arch = arch.lower()
+        if hash_type.lower() not in self._allowed_hashes:
+            raise ValueError('hash_type must be one of: {0}'.format(', '.join(self._allowed_hashes)))
+        else:
+            self.hash_type = hash_type.lower()
+        self.dest_dir = os.path.abspath(os.path.expanduser(dest_dir))
+        self.dest_file = dest_file
+        self.ver_file = ver_file
+        self.feed_url = feed_url
+        self.grub_cfg = grub_cfg
+        self.lckfile = os.path.abspath(os.path.expanduser(lock_path))
+        # From the JSON.
+        self.rel_notes_url = None
+        self.old_date = None
+        self.old_ver = None
+        self.old_hash = None
+        self.mirror_base = None
+        self.country = None
+        # New vals.
+        self.new_date = None
+        self.new_ver = None
+        self.new_hash = None
+        # Instance vars again.
+        self.do_update = False
+        self.force_update = False
+        self.iso_url = None
+        self.ipv4 = True
+        self.ipv6 = False
+        self.dest_iso = os.path.join(self.dest_dir, self.dest_file)
+        self.dest_ver = os.path.join(self.dest_dir, self.ver_file)
+        self._init_vars()
+
+    def _init_vars(self):
+        if self.getRunning():
+            return(None)
+        self.getCountry()
+        self.getNet()
+        self.getCurVer()
+        self.getNewVer()
+        return(None)
+
+    def main(self):
+        if self.getRunning():
+            return(None)
+        self.lock()
+        if self.do_update or \
+                self.force_update or not \
+                all((self.old_date,
+                     self.old_ver,
+                     self.old_hash)):
+            self.do_update = True
+            self.findMirror()
+            self.download()
+        self.touchVer()
+        self.unlock()
+        return(None)
+
+    def download(self):
+        if self.getRunning():
+            return(None)
+        if not any((self.do_update, self.force_update)):
+            return(None)
+        if not self.iso_url:
+            raise RuntimeError('iso_url attribute must be set first')
+        req = requests.get(self.iso_url, stream = True, headers = {'User-Agent': 'curl/7.74.0'})
+        if not req.ok:
+            raise RuntimeError('Received non-200/30x {0} for {1}'.format(req.status_code, self.iso_url))
+        with req as uri:
+            with open(self.dest_iso, 'wb') as fh:
+                shutil.copyfileobj(uri.raw, fh)
+        hasher = hashlib.new(self.hash_type)
+        with open(self.dest_iso, 'rb') as fh:
+            hasher.update(fh.read())
+        realhash = hasher.hexdigest().lower()
+        if realhash != self.new_hash:
+            raise RuntimeError('Hash mismatch: {0} (LOCAL), {1} (REMOTE)'.format(realhash, self.new_hash))
+        self.updateVer()
+        return(None)
+
+    def findMirror(self):
+        self.getCountry()
+        if self.mirror_base:
+            return(None)
+        for p in ('http', 'https'):
+            m = arch_mirror_ranking.MirrorIdx(country = self.country,
+                                              proto = 'http',
+                                              is_active = True,
+                                              ipv4 = self.ipv4,
+                                              ipv6 = self.ipv6,
+                                              isos = True,
+                                              statuses = False)
+            for s in m.ranked_servers:
+                try:
+                    req = requests.get(s['url'])
+                    if req.ok:
+                        self.mirror_base = s['url']
+                        break
+                except (OSError, ConnectionRefusedError):
+                    continue
+        return(None)
+
+    def getCountry(self):
+        if self.country:  # The API has limited number of accesses for free.
+            return(None)
+        url = 'https://ipinfo.io/country'
+        req = requests.get(url, headers = {'User-Agent': 'curl/7.74.0'})
+        if not req.ok:
+            raise RuntimeError('Received non-200/30x {0} for {1}'.format(req.status_code, url))
+        self.country = req.content.decode('utf-8').strip().upper()
+        return(None)
+
+    def getCurVer(self):
+        if self.getRunning():
+            return(None)
+        if not os.path.isfile(self.dest_ver):
+            self.do_update = True
+            self.force_update = True
+            self.old_ver = 0.00
+            return(None)
+        with open(self.dest_ver, 'rb') as fh:
+            ver_info = json.load(fh)
+        self.old_date = datetime.datetime.strptime(ver_info['date'], self._date_fmt)
+        self.old_ver = datetime.datetime.strptime(ver_info['ver'], self._datever_fmt)
+        self.old_hash = ver_info.get(self.hash_type, self._def_hash)
+        self.country = ver_info.get('country')
+        self.new_hash = self.old_hash
+        self.new_ver = self.old_ver
+        self.new_date = self.old_date
+        # if ver_info.get('arch') != self._arch:
+        #     self.do_update = True
+        #     self.force_update = True
+        try:
+            hasher = hashlib.new(self.hash_type)
+            with open(self.dest_iso, 'rb') as fh:
+                hasher.update(fh.read())
+            if self.old_hash != hasher.hexdigest().lower():
+                self.do_update = True
+                self.force_update = True
+        except FileNotFoundError:
+            self.do_update = True
+            self.force_update = True
+            return(None)
+        return(None)
+
+    def getNet(self):
+        for k in ('ipv4', 'ipv6'):
+            url = 'https://{0}.clientinfo.square-r00t.net'.format(k)
+            try:
+                req = requests.get(url)
+                setattr(self, k, req.json()['ip'])
+            except OSError:
+                setattr(self, k, False)
+        return(None)
+
+    def getNewVer(self):
+        if self.getRunning():
+            return(None)
+        if not self.mirror_base:
+            self.findMirror()
+        req = requests.get(self.feed_url, headers = {'User-Agent': 'curl/7.74.0'})
+        if not req.ok:
+            raise RuntimeError('Received non-200/30x {0} for {1}'.format(req.status_code, self.feed_url))
+        feed = etree.fromstring(req.content)
+        for item in feed.xpath('//item'):
+            date_xml = item.find('pubDate')
+            ver_xml = item.find('title')
+            notes_xml = item.find('link')
+            date = ver = notes = None
+            if date_xml is not None:
+                date = datetime.datetime.strptime(date_xml.text, self._date_fmt)
+            if ver_xml is not None:
+                ver = ver_xml.text
+            if notes_xml is not None:
+                notes = notes_xml.text
+            new_ver = datetime.datetime.strptime(ver, self._datever_fmt)
+            if not all((self.old_ver, self.old_date)) or \
+                    (new_ver > self.old_ver) or \
+                    (self.old_date < date):
+                self.do_update = True
+                self.new_ver = new_ver
+                self.new_date = date
+                self.rel_notes_url = notes
+                datever = self.new_ver.strftime(self._datever_fmt)
+                self.iso_url = os.path.join(self.mirror_base,
+                                            self._iso_file.lstrip('/')).format(ver = datever, arch = self._arch)
+                hash_url = os.path.join(self.mirror_base,
+                                        self._iso_dir,
+                                        '{0}sums.txt'.format(self.hash_type))
+                req = requests.get(hash_url, headers = {'User-Agent': 'curl/7.74.0'})
+                if not req.ok:
+                    raise RuntimeError('Received non-200/30x {0} for {1}'.format(req.status_code, hash_url))
+                hash_lines = req.content.decode('utf-8').strip().splitlines()
+                tgt_fname = os.path.basename(self.iso_url)
+                for line in hash_lines:
+                    if line.strip().startswith('#'):
+                        continue
+                    hash_str, fname = line.split()
+                    if fname != tgt_fname:
+                        continue
+                    self.new_hash = hash_str.lower()
+                    break
+            break
+        return(None)
+
+    def getRunning(self):
+        if not os.path.isfile(self.lckfile):
+            return(False)
+        my_pid = os.getpid()
+        with open(self.lckfile, 'r') as fh:
+            pid = int(fh.read().strip())
+        if not psutil.pid_exists(pid):
+            os.remove(self.lckfile)
+            return(False)
+        if pid == my_pid:
+            return(False)
+        return(True)
+
+    def lock(self):
+        with open(self.lckfile, 'w') as fh:
+            fh.write(str(os.getpid()))
+        return(None)
+
+    def touchVer(self):
+        if self.getRunning():
+            return(None)
+        ver_path = pathlib.Path(self.dest_ver)
+        ver_path.touch(exist_ok = True)
+        return(None)
+
+    def unlock(self):
+        if os.path.isfile(self.lckfile):
+            os.remove(self.lckfile)
+        return(None)
+
+    def updateVer(self):
+        if self.getRunning():
+            return(None)
+        d = {'date': self.new_date.strftime(self._date_fmt),
+             'mirror': self.mirror_base,
+             'country': self.country,
+             'notes': self.rel_notes_url,
+             'ver': self.new_ver.strftime(self._datever_fmt),
+             self.hash_type: self.new_hash}
+        j = json.dumps(d, indent = 4)
+        with open(self.dest_ver, 'w') as fh:
+            fh.write(j)
+            fh.write('\n')
+        return(None)
+
+
+if __name__ == '__main__':
+    u = Updater()
+    u.main()
diff --git a/sysresccd/relchk.py b/sysresccd/relchk.py
index 3d74bca..297ad3c 100755
--- a/sysresccd/relchk.py
+++ b/sysresccd/relchk.py
@@ -1,6 +1,13 @@
 #!/usr/bin/env python3
 
 # TODO: logging
+# Example .sysresccd.json:
+# {
+#     "date": "Sun, 22 Nov 2020 18:03:52 +0900",
+#     "arch": "amd64",
+#     "ver": 7.01,
+#     "sha512": "9d8c7e6d5c5f22d42bc20a663(...)"
+# }
 
 import datetime
 import json