Managing temporary files with systemd-tmpfiles on Red Hat Enterprise Linux 7

Have you ever used a temporary directory? I’m guessing if you use a computer, you’ve used one of these. It’s a core feature of nearly every operating-system.

To ensure system stability, you should always check that filesystems on which a temporary directory resides don’t get full — running out of space can quickly bring your system to a grinding halt.

One method to prevent running out of space could be to place those directories on a dedicated partition, but no matter the solution, it is a best practice to clean those directories periodically, based on your/your app’s needs.

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LTTng Packages now Available for Red Hat Enterprise Linux 7

EfficiOS is pleased to announce it is now providing LTTng packages for Red Hat Enterprise Linux 7, available today as part of its Enterprise Packages portal.

EfficiOS specialises in the research and development of open source performance analysis tools. As part of its activities, EfficiOS develops the Linux Tracing Toolkit: next generation for which it provides enterprise support, training and consulting services.

What is tracing?

Tracing is a technique used to understand the behaviour of a software system. In this regard, it is not far removed from logging. However, tracers and loggers are designed to accommodate very different use cases.

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Five different ways to handle leap seconds with NTP

A leap second is an adjustment that is once in a while applied to the Coordinated Universal Time (UTC) to keep it close to the mean solar time. The concept is similar to that of leap day, but instead of adding a 29th day to February to keep the calendar synchronized with Earth’s orbit around the Sun, an extra second 23:59:60 is added to the last day of June or December to keep the time of the day synchronized with the Earth’s rotation relative to the Sun. The mean solar day is about 2 milliseconds longer than 24 hours and in long term it’s getting longer as the Moon is constantly slowing down the Earth’s rotation.

UTC is based on the International Atomic Time (TAI) and it is currently 35 seconds behind TAI. The first leap second was inserted in 1972 and 25 seconds were inserted so far. The next one is scheduled for 30 June 2015, when the offset from TAI will increase to 36 seconds. Leap seconds are scheduled only about 6 months in advance.

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Writing an application that supports DNSSEC in RHEL and Fedora

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DNSSEC introduction

DNS is a distributed database that is capable of storing different types of data, not only IP addresses, in which the domain owner can publish various domain specific data. Yet, plain DNS does not offer any type of security measures. This means that DNS data in the response can be spoofed by anybody at any time.

This is where DNSSEC comes in. DNSSEC stands for DNS SECurity Extensions and brings the data authentication and data integrity check into the DNS world. The whole solution is based on asymmetric cryptography.

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Malloc systemtap probes: an example

gnu logoOne feedback I got from my blog post on Understanding malloc behavior using Systemtap userspace probes was that I should have included an example script to explain how this works. Well, better late than never, so here’s an example script. This script prints some diagnostic information during a program run and also logs some information to print out a summary at the end. I’ll go through the script a few related probes at a time.

global sbrk, waits, arenalist, mmap_threshold = 131072, heaplist

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