Author: Sahil Suri

4 Iotop command examples in Linux/Unix

Posted by | Oct 30, 2017 | , |

The iotop is a free and useful Linux top command like monitoring tool meant to monitor disk I/O activity on the server. You must have a kernel version of 2.6.20 or later to use iotop. It requires root privileges to execute. We could also use sar command or iostat to monitor I/O activity on the server, but iotop is different from these tools because it displays columns for the I/O bandwidth utilized by each process/thread during the sampling period. It also shows the percentage of time the thread/process spent while swapping in and while waiting on I/O. Having I/O utilization information based on process IDs instead of disks makes identification of processes causing I/O bottlenecks straightforward. The iotop is not available by default on most systems. So, let’s see the installation process on Redhat/Centos and Ubuntu/Debian based systems. Installing iotop on Debian/Ubuntu systems root@linuxnix:~# apt-get install iotop Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: iotop 0 upgraded, 1 newly installed, 0 to remove and 12 not upgraded. Need to get 23.8 kB of archives. After this operation, 127 kB of additional disk space will be used. Get:1 http://ap-southeast-1.ec2.archive.ubuntu.com/ubuntu/ trusty/universe iotop amd64 0.6-1 [23.8 kB] Fetched 23.8 kB in 0s (36.7 kB/s) Selecting previously unselected package iotop. (Reading database ... 118631 files and directories currently installed.) Preparing to unpack...

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ntptrace and ntpdate commands for debugging ntp

Posted by | Oct 27, 2017 | |

In this article, I’ll explain how we may use ntpdate and ntptrace commands while working o debugging or troubleshooting NTP related issues. We already showed how to install and configure NTP in Linux Redhat/Centos and Ubuntu/Debian. What is a ntpupdate command in Linux? The ntpdate command is used to manually sync time with an NTP server when you don’t have NTP agent running. Note: ntpdate will only sync to the time server if the ntpd daemon is not running. Install ntpupdate command in Linux This package is installed on the system, but if it isn’t we can easily install it via yum as shown below: [root@linuxnix ~]# yum install ntpdate -y Loaded plugins: fastestmirror, presto Setting up Install Process Determining fastest mirrors * base: mirror.nus.edu.sg * extras: mirror.nus.edu.sg * updates: mirror.nus.edu.sg base | 3.7 kB 00:00 centos-sclo-rh | 2.9 kB 00:00 centos-sclo-rh/primary_db | 2.6 MB 00:04 extras | 3.4 kB 00:00 extras/primary_db | 29 kB 00:00 updates | 3.4 kB 00:00 updates/primary_db | 4.7 MB 00:00 Resolving Dependencies --> Running transaction check ---> Package ntpdate.x86_64 0:4.2.6p5-10.el6.centos.2 will be installed --> Finished Dependency Resolution Dependencies Resolved ============================================================================================================================================================================================================== Package Arch Version Repository Size ====================================================================================================================================== Installing: ntpdate x86_64 4.2.6p5-10.el6.centos.2 base 78 k Transaction Summary ====================================================================================================================================== Install 1 Package(s) Total download size: 78 k Installed size: 123 k Downloading Packages: Setting up and reading Presto delta metadata Processing delta metadata Package(s) data still...

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Configure NTP Server on Centos/Redhat and Ubuntu/Debian

Posted by | Oct 26, 2017 | , |

What is NTP? Accurate system time is essential for the software and applications installed on the server to be able to operate correctly. NTP synchronizes very critically for financial and telemetric applications. The issue with system clock is with the passage of time; the system clock may become inaccurate owing to a variety of reasons like power failures, cheap hardware clocks, etc. To buy a uber accurate and costly crystal clock for each system is not a viable solution. This is where the Network Time Protocol (NTP) comes into the picture. What are NTP server and client? The NTP server: As said earlier to have an accurate and costly clock for each and every system is not a good solution. Thats where we have NTP servers on the Internet which have precise system times with the help of costly time crystal clocks.  These servers intern synchronize with other NTP servers to have accurate system clocks. The NTP client: These are just NTP agents which keep local system time synchronize with internet-based or local NTP servers for keeping local time not to drift away. What actually NTP service do constantly monitor Internet-based NTP servers operates on UDP port number 123 and is used to synchronize system time with a reference source. The reference source, in this case, could be another server or a GPS clock. The package is generally installed on the...

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My name is Surendra Kumar Anne. I hail from Vijayawada which is cultural capital of south Indian state of Andhra Pradesh. I am a Linux evangelist who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. At present I work at Bank of America as Sr. Analyst Systems and Administration. You can contact me at surendra (@) linuxnix dot com.