Linux时间同步脚本

由于实际要求，需要让 Linux 系统的时间和局域网的其他设备保持同步。为了实现上述目标，本文使用 NTP 协议进行时间同步。

由于是局域网环境，不适合直接从互联网上获取当前时间进行时间同步。为此本文采用了在局域网内搭建 NTP 服务器，所有的 Linux 设备都通过向该服务器同步时间，从而保证局域网内的设备时间保持同步。

本文使用 Windows Server 2012 搭建 NTP 服务器， Windows 配置 NTP 服务器可以使用以下方法：

• 通过配置注册表实现，但是操作太麻烦；
• 安装 SNTP Service 软件，安装该软件后默认开启 SNTP 服务，然后就可以使用 NTP 客户端进行时间同步了。

本文采用第二种方法，简单方便。下面是搭建步骤：

1. 下载 SNTP Service 软件 进入 SNTP Service 软件官网下载该软件。

2. 点击安装 SNTP Service 软件

3. 点击 next

4. 选择安装目录，并点击 next

5. 自定义安装组件，并点击 next

6. 并点击 install 进入安装

7. 等待安装完成

8. 安装完成

经过上述步骤后， SNTP 服务就开启了，可以使用 NTP 客户端进行时间同步了。

本文使用 Python 脚本编写 NTP 客户端脚本 ntpclient.py ，使用该脚本访问搭建好的 NTP 服务器获取当前时间。该脚本是基于 ntplib 库， 其源码如下所示：

#-*- coding:utf-8 -*-################################################################################ ntplib - Python NTP library.# Copyright (C) 2009 Charles-Francois Natali <cf.natali@Gmail.com>## ntplib is free software; you can redistribute it and/or modify it under the# terms of the GNU Lesser General Public License as published by the Free# Software Foundation; either version 2 of the License, or (at your option) any# later version.## This PRogram is distributed in the hope that it will be useful, but WITHOUT# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more# details.## You should have received a copy of the GNU Lesser General Public License# along with this program; if not, write to the Free Software Foundation, 51# Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA###############################################################################"""Python NTP library.Implementation of client-side NTP (RFC-1305), and useful NTP-relatedfunctions."""import osimport sysimport datetimeimport socketimport structimport timefrom optparse import OptionParserclass NTPException(Exception):    """Exception raised by this module."""    passclass NTP:    """Helper class defining constants."""    _SYSTEM_EPOCH = datetime.date(*time.gmtime(0)[0:3])    """system epoch"""    _NTP_EPOCH = datetime.date(1900, 1, 1)    """NTP epoch"""    NTP_DELTA = (_SYSTEM_EPOCH - _NTP_EPOCH).days * 24 * 3600    """delta between system and NTP time"""    REF_ID_TABLE = {        "GOES":  "Geostationary Orbit Environment Satellite",        "GPS/0": "Global Position System",        "GAL/0": "Galileo Positioning System",        "PPS/0": "Generic pulse-per-second",        "IRIG":  "Inter-Range Instrumentation Group",        "WWVB":  "LF Radio WWVB Ft. Collins, CO 60 kHz",        "DCF/0": "LF Radio DCF77 Mainflingen, DE 77.5 kHz",        "HBG/0": "LF Radio HBG Prangins, HB 75 kHz",        "MSF/0": "LF Radio MSF Anthorn, UK 60 kHz",        "JJY/0": "LF Radio JJY Fukushima, JP 40 kHz, Saga, JP 60 kHz",        "LORC":  "MF Radio LORAN C station, 100 kHz",        "TDF/0": "MF Radio Allouis, FR 162 kHz",        "CHU/0": "HF Radio CHU Ottawa, Ontario",        "WWV/0": "HF Radio WWV Ft. Collins, CO",        "WWVH":  "HF Radio WWVH Kauai, HI",        "NIST":  "NIST telephone modem",        "ACTS":  "NIST telephone modem",        "USNO":  "USNO telephone modem",        "PTB/0": "European telephone modem",        "LOCL":  "uncalibrated local clock",        "CESM":  "calibrated Cesium clock",        "RBDM":  "calibrated Rubidium clock",        "OMEG":  "OMEGA radionavigation system",        "DCN/0": "DCN routing protocol",        "TSP/0": "TSP time protocol",        "DTS/0": "Digital Time Service",        "ATOM":  "Atomic clock (calibrated)",        "VLF/0": "VLF radio (OMEGA,, etc.)",        "1PPS":  "External 1 PPS input",        "FREE":  "(Internal clock)",        "INIT":  "(Initialization)",        "/0/0/0/0":   "NULL",    }    """reference identifier table"""    STRATUM_TABLE = {        0: "unspecified or invalid",        1: "primary reference (%s)",    }    """stratum table"""    MODE_TABLE = {        0: "reserved",        1: "symmetric active",        2: "symmetric passive",        3: "client",        4: "server",        5: "broadcast",        6: "reserved for NTP control messages",        7: "reserved for private use",    }    """mode table"""    LEAP_TABLE = {        0: "no warning",        1: "last minute of the day has 61 seconds",        2: "last minute of the day has 59 seconds",        3: "unknown (clock unsynchronized)",    }    """leap indicator table"""class NTPPacket:    """NTP packet class.    This represents an NTP packet.    """    _PACKET_FORMAT = "!B B B b 11I"    """packet format to pack/unpack"""    def __init__(self, version=2, mode=3, tx_timestamp=0):        """Constructor.        Parameters:        version      -- NTP version        mode         -- packet mode (client, server)        tx_timestamp -- packet transmit timestamp        """        self.leap = 0        """leap second indicator"""        self.version = version        """version"""        self.mode = mode        """mode"""        self.stratum = 0        """stratum"""        self.poll = 0        """poll interval"""        self.precision = 0        """precision"""        self.root_delay = 0        """root delay"""        self.root_dispersion = 0        """root dispersion"""        self.ref_id = 0        """reference clock identifier"""        self.ref_timestamp = 0        """reference timestamp"""        self.orig_timestamp = 0        """originate timestamp"""        self.recv_timestamp = 0        """receive timestamp"""        self.tx_timestamp = tx_timestamp        """tansmit timestamp"""    def to_data(self):        """Convert this NTPPacket to a buffer that can be sent over a socket.        Returns:        buffer representing this packet        Raises:        NTPException -- in case of invalid field        """        try:            packed = struct.pack(NTPPacket._PACKET_FORMAT,                (self.leap << 6 | self.version << 3 | self.mode),                self.stratum,                self.poll,                self.precision,                _to_int(self.root_delay) << 16 | _to_frac(self.root_delay, 16),                _to_int(self.root_dispersion) << 16 |                _to_frac(self.root_dispersion, 16),                self.ref_id,                _to_int(self.ref_timestamp),                _to_frac(self.ref_timestamp),                _to_int(self.orig_timestamp),                _to_frac(self.orig_timestamp),                _to_int(self.recv_timestamp),                _to_frac(self.recv_timestamp),                _to_int(self.tx_timestamp),                _to_frac(self.tx_timestamp))        except struct.error:            raise NTPException("Invalid NTP packet fields.")        return packed    def from_data(self, data):        """Populate this instance from a NTP packet payload received from        the network.        Parameters:        data -- buffer payload        Raises:        NTPException -- in case of invalid packet format        """        try:            unpacked = struct.unpack(NTPPacket._PACKET_FORMAT,                    data[0:struct.calcsize(NTPPacket._PACKET_FORMAT)])        except struct.error:            raise NTPException("Invalid NTP packet.")        self.leap = unpacked[0] >> 6 & 0x3        self.version = unpacked[0] >> 3 & 0x7        self.mode = unpacked[0] & 0x7        self.stratum = unpacked[1]        self.poll = unpacked[2]        self.precision = unpacked[3]        self.root_delay = float(unpacked[4])/2**16        self.root_dispersion = float(unpacked[5])/2**16        self.ref_id = unpacked[6]        self.ref_timestamp = _to_time(unpacked[7], unpacked[8])        self.orig_timestamp = _to_time(unpacked[9], unpacked[10])        self.recv_timestamp = _to_time(unpacked[11], unpacked[12])        self.tx_timestamp = _to_time(unpacked[13], unpacked[14])class NTPStats(NTPPacket):    """NTP statistics.    Wrapper for NTPPacket, offering additional statistics like offset and    delay, and timestamps converted to system time.    """    def __init__(self):        """Constructor."""        NTPPacket.__init__(self)        self.dest_timestamp = 0        """destination timestamp"""    @property    def offset(self):        """offset"""        return ((self.recv_timestamp - self.orig_timestamp) +                (self.tx_timestamp - self.dest_timestamp))/2    @property    def delay(self):        """round-trip delay"""        return ((self.dest_timestamp - self.orig_timestamp) -                (self.tx_timestamp - self.recv_timestamp))    @property    def tx_time(self):        """Transmit timestamp in system time."""        return ntp_to_system_time(self.tx_timestamp)    @property    def recv_time(self):        """Receive timestamp in system time."""        return ntp_to_system_time(self.recv_timestamp)    @property    def orig_time(self):        """Originate timestamp in system time."""        return ntp_to_system_time(self.orig_timestamp)    @property    def ref_time(self):        """Reference timestamp in system time."""        return ntp_to_system_time(self.ref_timestamp)    @property    def dest_time(self):        """Destination timestamp in system time."""        return ntp_to_system_time(self.dest_timestamp)class NTPClient:    """NTP client session."""    def __init__(self):        """Constructor."""        pass    def request(self, host, version=2, port='ntp', timeout=5):        """Query a NTP server.        Parameters:        host    -- server name/address        version -- NTP version to use        port    -- server port        timeout -- timeout on socket Operations        Returns:        NTPStats object        """        # lookup server address        addrinfo = socket.getaddrinfo(host, port)[0]        family, sockaddr = addrinfo[0], addrinfo[4]        # create the socket        s = socket.socket(family, socket.SOCK_DGRAM)        try:            s.settimeout(timeout)            # create the request packet - mode 3 is client            query_packet = NTPPacket(mode=3, version=version,                                tx_timestamp=system_to_ntp_time(time.time()))            # send the request            s.sendto(query_packet.to_data(), sockaddr)            # wait for the response - check the source address            src_addr = None,            while src_addr[0] != sockaddr[0]:                response_packet, src_addr = s.recvfrom(256)            # build the destination timestamp            dest_timestamp = system_to_ntp_time(time.time())        except socket.timeout:            raise NTPException("No response received from %s." % host)        finally:            s.close()        # construct corresponding statistics        stats = NTPStats()        stats.from_data(response_packet)        stats.dest_timestamp = dest_timestamp        return statsdef _to_int(timestamp):    """Return the integral part of a timestamp.    Parameters:    timestamp -- NTP timestamp    Retuns:    integral part    """    return int(timestamp)def _to_frac(timestamp, n=32):    """Return the fractional part of a timestamp.    Parameters:    timestamp -- NTP timestamp    n         -- number of bits of the fractional part    Retuns:    fractional part    """    return int(abs(timestamp - _to_int(timestamp)) * 2**n)def _to_time(integ, frac, n=32):    """Return a timestamp from an integral and fractional part.    Parameters:    integ -- integral part    frac  -- fractional part    n     -- number of bits of the fractional part    Retuns:    timestamp    """    return integ + float(frac)/2**ndef ntp_to_system_time(timestamp):    """Convert a NTP time to system time.    Parameters:    timestamp -- timestamp in NTP time    Returns:    corresponding system time    """    return timestamp - NTP.NTP_DELTAdef system_to_ntp_time(timestamp):    """Convert a system time to a NTP time.    Parameters:    timestamp -- timestamp in system time    Returns:    corresponding NTP time    """    return timestamp + NTP.NTP_DELTAdef leap_to_text(leap):    """Convert a leap indicator to text.    Parameters:    leap -- leap indicator value    Returns:    corresponding message    Raises:    NTPException -- in case of invalid leap indicator    """    if leap in NTP.LEAP_TABLE:        return NTP.LEAP_TABLE[leap]    else:        raise NTPException("Invalid leap indicator.")def mode_to_text(mode):    """Convert a NTP mode value to text.    Parameters:    mode -- NTP mode    Returns:    corresponding message    Raises:    NTPException -- in case of invalid mode    """    if mode in NTP.MODE_TABLE:        return NTP.MODE_TABLE[mode]    else:        raise NTPException("Invalid mode.")def stratum_to_text(stratum):    """Convert a stratum value to text.    Parameters:    stratum -- NTP stratum    Returns:    corresponding message    Raises:    NTPException -- in case of invalid stratum    """    if stratum in NTP.STRATUM_TABLE:        return NTP.STRATUM_TABLE[stratum] % (stratum)    elif 1 < stratum < 16:        return "secondary reference (%s)" % (stratum)    elif stratum == 16:        return "unsynchronized (%s)" % (stratum)    else:        raise NTPException("Invalid stratum or reserved.")def ref_id_to_text(ref_id, stratum=2):    """Convert a reference clock identifier to text according to its stratum.    Parameters:    ref_id  -- reference clock indentifier    stratum -- NTP stratum    Returns:    corresponding message    Raises:    NTPException -- in case of invalid stratum    """    fields = (ref_id >> 24 & 0xff, ref_id >> 16 & 0xff,              ref_id >> 8 & 0xff, ref_id & 0xff)    # return the result as a string or dot-formatted IP address    if 0 <= stratum <= 1:        text = '%c%c%c%c' % fields        if text in NTP.REF_ID_TABLE:            return NTP.REF_ID_TABLE[text]        else:            return "Unidentified reference source '%s'" % (text)    elif 2 <= stratum < 255:        return '%d.%d.%d.%d' % fields    else:        raise NTPException("Invalid stratum.")if __name__ == '__main__':'''if len(sys.argv) <= 1:print "error, parameters is invalid!"exit(1)'''# 解析用户输入的参数parser = OptionParser(version="%prog 0.1") # 获取参数的选项parser.add_option("-u", "--url", action="store",type="string", dest="url",help="the url of ntp server.")(options, args) = parser.parse_args()if options.url == None:print "error, url is invalid!"exit(1)# 建立NTP客户端client = NTPClient()response = client.request(options.url, version=3)# 从NTP服务器获得当前时间cur = time.ctime(response.tx_time)# 打印当前时间print "%s" %cur

上述客户端脚本只是从 NTP 服务器获取当前时间，而不能设置 Linux 当前时间。为实现该功能，本文创建 Shell 脚本 time_demo.sh 来更新 Linux 的时间。其源码如下所示：

#!/bin/bash # 将本文件和 ntpclient.py 放在同一目录下time=`python ./ntpclient.py -u 172.16.177.212`date -s "$time" > /dev/null

[root@00:B3:42:01:02:23 bin]# dateMon Aug  9 00:00:03 CST 2010[root@00:B3:42:01:02:23 bin]# ./time_demo.sh [root@00:B3:42:01:02:23 bin]# dateFri Nov 21 17:04:09 CST 2014