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Image of Advanced Programming in the UNIX Environment, Second Edition (Addison-Wesley Professional Computing Series)
Image of Linux Kernel Development (3rd Edition)
Image of XSLT 2.0 and XPath 2.0 Programmer's Reference (Programmer to Programmer)
Image of Operating System Concepts

RHCSA Preparation - Script to Configure a Simple OpenLDAP Server

The ability to quickly configure an LDAP (Lightweight Directory Access Protocol) client for accessing user and group accounts is one of the skills you are expected to have when you sit the Red Hat RHSCA exam. LDAP is a application-level protocol for accessing and maintaining distributed directory services over an IP-based network. It is specified in a series of RFCs (Request for Comments) using ASN.1. The latest LDAP specification is Version 3, published as RFC 4511. Typically, at a minimum, LDAP is used to facilitate centralized user and group account administration. Instead of storing user and group account information locally

My Thoughts on Systemd on RHEL7

From the earliest days of systemd, I have been opposed to the technology as far as it’s use on enterprise servers is concerned. Now that RHEL7 (Red Hat Enterprise Linux v7), which uses systemd instead of upstart, is starting to replace older versions of RHEL in enterprise and DOD environments, I thought I would revisit the issue. My technical reasons for opposing systemd on servers are as follows: There is no guarantee that services will be started in the same order each time a server is rebooted. Logs are binary, non-transactional and in a different format than previously. This means

Revisiting Systemd D-Bus Interfaces

In a May 2013 blog post I examined the then systemd D-Bus interface. At that time the systemd version string was 208. In this short blog I will discuss hostnamectl/hostnamed and timedatectl/timedatectl functionality as it relates to the systemd Dbus. You can use the following dbus-send command to find out what’s available on the D-Bus system bus: # dbus-send –system –print-reply –dest=”org.freedesktop.DBus” \ /org/freedesktop/DBus org.freedesktop.DBus.ListActivatableNames method return sender=org.freedesktop.DBus -> dest=:1.137 reply_serial=2 array [ string “org.freedesktop.DBus” string “org.freedesktop.login1” string “org.fedoraproject.Setroubleshootd” string “org.freedesktop.machine1” string “org.freedesktop.ColorManager” string “com.redhat.problems.configuration” string “org.freedesktop.systemd1” string “org.freedesktop.Avahi” string “org.freedesktop.PolicyKit1” string “org.freedesktop.ModemManager1” string “org.bluez” string “org.freedesktop.hostname1” string “org.freedesktop.NetworkManager” string

Control Group Subsystems in RHEL7

Control groups (cgroups) are a Linux kernel feature that enables you to allocate resources — such as CPU time, system memory, disk I/O, network bandwidth, etc. — among hierarchically ordered groups of processes running on a system. Initially developed by Google engineers Paul Menage and Rohit Seth in 2006 under the name “process containers”, it was merged into kernel version 2.6.24 and extensively enhanced since then. RHEL6 was the first Red Hat distribution to support cgroups. Cgroups provide system administrators with fine-grained control over allocating, prioritizing, denying, managing, and monitoring system resources. A cgroup is a collection of processes that

Boycott Systemd

Finally people are beginning to wake up and understand that systemd and Lennart Poettering, who works for Red Hat, is a cancer that will destroy and splinter the Linux ecosystem. According to a new movement, boycottsystemd.org: It represents a monumental increase in complexity, an abhorrent and violent slap in the face to the Unix philosophy, and its inherent domineering and viral nature turns it into something akin to a “second kernel” that is spreading all across the Linux ecosystem. I could not agree more. systemd flies in the face of the Unix philosophy: “do one thing and do it well,”