Time is important for systems because all work done according to time and logs get their timestamps. Normally server hardware provides time but it can be false over time because the hardware clock is not precise. Ntp is a protocol designed to get time info from the network. NTP can also provide date and time information to other servers as a daemon. NTP full name is Network Time Protocol.
Install Ntpdate
Ntpdate is simple and fast ntp client used to get information about time.
CentOS, Fedora, Red Hat
$ yum install ntpdate -y
Ubuntu, Debian, Mint, Kali
$ sudo apt-get install ntpdate
Get Time From Ntp Server
We can use ntpdate client to get the current time from the NTP server. We will specify the NTP server as a parameter to the ntpdate command.
$ sudo ntpdate ntp.ubuntu.com 16 Nov 07:06:12 ntpdate[4551]: adjust time server 91.189.89.199 offset -0.000030 sec
We need root privileges to use ntpdate to sync clock
Check Current Time From Local Server
We can list current time in the server by using date command.
$ date Wed Nov 16 07:07:42 +03 2016
Enable Firewall For Ntp Related Ports
We may need to open ports about NTP like below by using iptables
$ iptables -A output -p udp -s 192.168.1.1 --sport 1024:65535 -d 0/0 --dport 123 -m state --state NEW,ESTABLISHED -j ACCEPT $ iptables -A input -p udp -s 0/0 --sport 123 -d 192.168.1.1 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT
Get Current Time Info
ntpdate is an old tool and deprecated we can use datetimectl according to ntpdate
$ timedatectl status
We see that our time is synchronized with ntp with “NTP synchronized” line.
How To Synchronize System Time In Linux? Infographic
