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Time Server

由 datahunter 在 一, 30/04/2012 - 17:20 發表

最後更新: 2022-07-19

 

目錄

 

date

 

設定:

date [-u|--utc|--universal]  FORMAT

opts:

  • -u,--utc
  • -s,--set (-s, --set=STRING)
  • -d,--date TIME  Display TIME, not 'now'
  • -R,--rfc-2822   Output RFC-2822 compliant date string (Sat, 01 Jan 2000 01:02:42 +0000)

FORMAT:

  • hh:mm[:ss]
  • YYYY-MM-DD hh:mm[:ss]

e.g.

date -s "2000-01-01 01:01"

 

# Display Format

date +%s

P.S.

%s        Epoch

%Y        year
%m       month (01..12)
%d        day of month (e.g, 01)
%k        hour ( 0..23)
%M        minute (00..59)
%S        second (00..60)

%F     full date; same as %Y-%m-%d

 

# Display time described by STRING

Usage

-d, --date=STRING

date +%s -d"Jan 1, 1980 00:00:01"

315504001

date -d @1190000000

output:

Mon Sep 17 11:33:20 HKT 2007

# Time Zone

tzconfig

tzselect

 

hwclock

 

查看當時時間

hwclock (相當於 hwclock --show --utc 縮寫 hwclock -r -u)

Output

Thu 08 Nov 2018 05:19:37 PM HKT  -1.005565 seconds

Remark

ISO 8601 format.

The time shown is always in local time, even if you keep your Hardware Clock in UTC.

UTC or the local timescale

The Hardware Clock may be configured to use either the UTC or the local timescale

Indicate which timescale the Hardware Clock is set to.

  • --localtime
  • --utc, -u (Default)

hwclock --localtime

Thu 08 Nov 2018 09:26:07 AM HKT  -0.360894 seconds

hwclock --utc

Thu 08 Nov 2018 05:26:12 PM HKT  -0.360834 seconds

互 sync

hwclock --hctosys      # -s

hwclock --systohc      # -w

設定時間:

hwclock --set --date=newdate

Example:

hwclock --set --date="2011-08-14 16:45:05"

* local time

有關檔案

/etc/default/rcS:

# assume that the BIOS clock is set to UTC time (recommended)
UTC=no

 

ntpdate

 

Centos6 Package:

yum install ntpdate

更新系統時間:

ntpdate stdtime.gov.hk

Options:

-d     Enable the debugging mode
-u     Direct  ntpdate  to use an unprivileged port for outgoing packets.

Trobleshoot:

1:

 2 Jul 10:25:06 ntpdate[24686]: the NTP socket is in use, exiting

# 原因:  ntpd service 是啟動狀態導致無法使用 ntpdate

 

Debian

 

/usr/sbin/ntpdate-debian 與 ntpdate 是一樣的 program.

它們分別在它會讀取

  • /etc/default/ntpdate
  • /etc/ntp.conf

去更新時間

# /etc/ntp.conf

NTPDATE_USE_NTP_CONF=yes
NTPSERVERS="ntp.ubuntu.com"
  • -q     Query only - don't set the clock.
  • -d     Enable  the debugging mode
  • -u     Direct ntpdate to use an unprivileged port for outgoing packets.
22 Jul 09:40:23 ntpdate[26930]: ntpdate [email protected] Tue Jun  5 20:12:09 UTC 2012 (1)
Looking for host stdtime.gov.hk and service ntp
host found : 118.143.17.82
transmit(118.143.17.82)
receive(118.143.17.82)
transmit(118.143.17.82)
receive(118.143.17.82)
transmit(118.143.17.82)
receive(118.143.17.82)
transmit(118.143.17.82)
receive(118.143.17.82)
transmit(118.143.17.82)
server 118.143.17.82, port 123
stratum 1, precision -19, leap 00, trust 000
refid [MRS], delay 0.02773, dispersion 0.00005
transmitted 4, in filter 4
reference time:    d5970c10.095f035a  Mon, Jul 22 2013  9:40:32.036
originate timestamp: d5970c14.772ed3bc  Mon, Jul 22 2013  9:40:36.465
transmit timestamp:  d5970c11.14e85899  Mon, Jul 22 2013  9:40:33.081
filter delay:  0.02924  0.02782  0.02802  0.02773
         0.00000  0.00000  0.00000  0.00000
filter offset: 3.382756 3.382675 3.382854 3.382739
         0.000000 0.000000 0.000000 0.000000
delay 0.02773, dispersion 0.00005
offset 3.382739

22 Jul 09:40:35 ntpdate[26930]: step time server 118.143.17.82 offset 3.382739 sec

 

Openwrt - NTP

( 由 BusyBox v1.19.4 提供 )

它是同一個 Program 提供了 Server 及 Client 的功能的

NTP client/server:

        -d             Verbose
        -n             Do not daemonize
        -q             Quit after clock is set
        -N             Run at high priority
        -w             Do not set time (only query peers), implies -n
        -l              Run as server on port 123
        -S PROG    Run PROG after stepping time, stratum change, and every 11 mins
        -p PEER     Obtain time from PEER (may be repeated)

start up script:

/etc/init.d/sysntpd [start|Stop|enable|disable]

 

Query only:

行以下 command 之後鍵入 "Ctrl + c"

ntpd -q 0.openwrt.pool.ntp.org

-q     Query only - don't set the clock.

config:

/etc/config/system

config timeserver 'ntp'
        list server '0.openwrt.pool.ntp.org'
        list server '1.openwrt.pool.ntp.org'
        list server '2.openwrt.pool.ntp.org'
        list server '3.openwrt.pool.ntp.org'
        option enable_server '0'

 

Attack Description

 

NTP amplification is essentially a type of reflection attack. Reflection attacks involve eliciting a response from a server to a spoofed IP address. The attacker sends a packet with a forged IP address (the victim’s) and the server replies to this address.

Reflection attacks are dangerous. But they are even more dangerous when amplified. “Amplification,” in this context,

In an NTP amplification attack, the query-to-response ratio is anywhere between 20:1 and 200:1 or more.

 

Public Time Server

 

  • time.google.com
  • stdtime.gov.hk               # 香港天文台

 

限 IP

time.google.com 它一共有4架server, 分別係

  • time1.google.com
  • time2.google.com
  • time3.google.com
  • time4.google.com
chain=input action=accept protocol=udp src-address-list=GoogleNTP dst-address-list=RouterIP
    in-interface=eth16-mgt src-port=123 dst-port=123

 

Sync time scripts

 

/root/scripts/synctime.sh

/usr/sbin/ntpdate time.google.com > /dev/null 2>&1
hwclock -w > /dev/null 2>&1

 

timesyncd

 

On Ubuntu 20 LTS, ystemd-timesyncd.service is running by default on

Config

/etc/systemd/timesyncd.conf

A space-separated list of NTP server host names or IP addresses.
systemd-timesyncd will contact all configured system or
per-interface servers in turn until one is found that responds.

NTP=time.google.com

# the maximum estimated time required for a packet to travel to the server we are connected to from the server with the reference clock.
# If the current server does not satisfy this limit, systemd-timesyncd will switch to a different server

RootDistanceMaxSec=5

# 多久 refresh  一次

# Default Settings
PollIntervalMinSec=32
PollIntervalMaxSec=2048

Service

systemctl restart systemd-timesyncd

timedatectl timesync-status

 

 

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