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This article mainly introduces "how to solve centos time asynchrony". In daily operation, I believe many people have doubts about how to solve the problem of centos time asynchrony. The editor consulted all kinds of data and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts of "how to solve centos time asynchrony"! Next, please follow the editor to study!

First, update the time from the time server with ntpdate

If your linux system does not have the command ntpdate at all

Yum install ntp

After the installation, you don't have to do any configuration, and you don't need to test it directly.

The code is as follows:

[root@localhost ~] # ntpdate time.nist.gov

22 Oct 21:11:43 ntpdate [5014]: adjust time server 207.200.81.113 offset-0.018788 sec

If you go out of the above description, the synchronization is successful. Then add the following to the crontab.

1.Placement 10 * ntpdate time.nist.gov # domain name or IP

Synchronize every ten minutes. Recommend several time servers.

Time.nist.gov

Time.nuri.net

Asia.pool.ntp.org

Asia.pool.ntp.org

Asia.pool.ntp.org

Asia.pool.ntp.org

Second, use ntp to build your own time server.

Above we use other people's time servers to synchronize time, these time servers are more authoritative. When we build our own time server, we don't use crontab to run regularly.

1. Install the time server ntp

1.yum install ntp

2, configure ntp

The code is as follows

[root@localhost ~] # cat / etc/ntp.conf | awk'{if ($0! ~ / ^ $/ & & $0! ~ / ^ # /) {print $0}}'

Restrict default ignore / / does not allow you to modify or query ntp by default, and does not receive special packets

Restrict 127.0.0.1 / / gives all permissions to this machine

Restrict 192.168.1.0 mask 255.255.255.0 notrap nomodify / / machines on the LAN have permission to synchronize time

Server time.nist.gov prefer / / set time server, plus prefer means priority

Server 0.asia.pool.ntp.org

Server 1.asia.pool.ntp.org

Server 2.asia.pool.ntp.org

Server 127.127.1.0 # local clock

Fudge 127.127.1.0 stratum 10

Driftfile / var/lib/ntp/drift

Keys / etc/ntp/keys

3. Start ntp

[root@localhost ~] # / etc/init.d/ntpd start

4, view and test

The code is as follows:

[root@localhost ~] # netstat-upnl | grep ntpd / / View schedule

[root@localhost ~] # ntpq-pn / / View synchronized server IP

Remote refid st t when poll reach delay offset jitter

=

50.77.217.185.INIT .16u-64 0 0.000 0.000 0.000

202.90.158.4. Int. 16u-64 0 0.000 0.000 0.000

202.71.100.89. Int. 16u-64 0 0.000 0.000 0.000

202.134.1.10 .INIT. 16u-64 0 0.000 0.000 0.000

* 127.127.1.0. LOCL. 10 l 18 64 377 0.000 0.000 0.001

[root@localhost ~] # ntpstat / / result of synchronization

Synchronised to local net at stratum 11

Time correct to within 12 ms

Polling server every 512 s

Remote: that is, the IP or host name of the NTP host. Pay attention to the leftmost symbol. If "+" represents the upper NTP that is currently working on the clock, if it is "*", it means that it is also connected, but as a secondary online NTP host.

Refid: the address of the upper-level NTP host referenced

St: the stratum class

When: time synchronization update was done a few seconds ago

Poll: the next update is in a few seconds

Reach: the number of updates that have been requested from the upper NTP server

Delay: the time of clock delay during network transmission

Offset: the result of time compensation

Difference time between jitter:Linux system time and BIOS hardware time

Recommend the first method, although it is relatively simple to build a time server, but I do not think this is necessary. If you use someone else's time server, synchronize every 10 minutes, which can be accurate to milliseconds.

Author: undersea goshawk

Solution to the inconsistency between CentOS system time and UTC time

Install centos and find out that date is not the time we want. What should we do?

1. Vi / etc/sysconfig/clock # Editing time profile

ZONE= "Asia/Shanghai"

UTC=false # is set to false, and the hardware clock is not consistent with utc time.

ARC=false

2. The time zone of ln-sf / usr/share/zoneinfo/Asia/Shanghai / etc/localtime # linux is set to Shanghai time zone

3. Ntpdate 192.43.244.18 # alignment time

If you do not have a ntp server installed, you just need to execute the following command:

Yum install ntp # install ntp server

4. / sbin/hwclock-- systohc # set hardware time and system time consistent and calibrated

Well, our CentOS linux system time and computer hardware time are finally cst time, and both are in the Shanghai time zone, which is finally normal.

The ultimate solution of centos vps modification time and zone asynchrony

Due to the first use of domestic hyper-v architecture VPS and before buying to specify windows or centos system, because there is no reinstalled panel, for I am used to using debian is really torture, encountered a variety of minor problems in the process of operation. Ask customer service directly only understand winows environment, let you install WIN you have to install linux. Well, centos will have to fumble on his own. Because hyper-v is a virtualization product of Microsoft, it does not support linux earlier, and because of the corporate operation of debian, debian has entered a stage of rapid development, and even google has abandoned linux customization and turned to the debian development camp, which makes Microsoft feel some pressure, so Microsoft has pulled up centos, which is why hyper-v only supports centos, but does not support other linux derivative versions, and the support is not so reliable. After complaining, let's get to the point.

Topic: the time of installing lnmp in centos5.5 VPS of hyper-v architecture is out of sync, resulting in some functions of the website can not be used.

All kinds of methods found on the Internet failed. Then I looked for some documents carefully and finally got it done.

The time management of linux is strange that it is divided into system time and hardware time and subdivided into what UTC time. -_-|.

Hardware time is basically a CMOS clock.

Linux check hardware time: hwclock-- show

Linux View system time: date-R

Time and time zone synchronization for centos VPS.

System time part:

1. Edit the time zone profile: vi / etc/sysconfig/clock

ZONE= "Asia/Shanghai"

UTC=false # set UTC to false off

ARC=false

two。 Run the following command

# Delete default configuration

Rm-rf / etc/localtime

# reassign configuration

Ln-s / usr/share/zoneinfo/Asia/Shanghai / etc/localtime

# synchronize system time

Ntpdate-u pool.ntp.org

3. Hardware time part:

# adjust the hardware time to be consistent with the current system clock.

Hwclock-systohc

Or clock-- systohc

# forcing the system time to be written into CMOS to prevent restart failure

Hwclock-w

Or clock-w

Although the above steps have been successful, the time of my centos system of hyper-v architecture is not right. It can be a few minutes faster every day.

It can be solved by synchronizing the time with crontab.

# Editing the schedule

Vi / etc/crontab

# add the following line at the end of the table

30 5 * root / usr/sbin/ntpdate-u pool.ntp.org & & / sbin/clock-- systohc

# synchronize time at 05:30 every day. Clock-- systohc means hard disk time synchronizes system time.

At this point, the study on "how to solve the problem of centos time asynchrony" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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