systemd article slash editorial

Doing some reading on systemd, and found this interesting article.

I come from the old SystemV Release 4 days, so some of this new-fangled stuff like systemd has a bit of a learning curve adjustment (old dog new tricks).

The author here writes an editorial opinion on systemd.

http://www.infoworld.com/article/2608798/data-center/systemd--harbinger-of-the-linux-apocalypse.html

The sysctl interface for system tuning on Linux

I looked into sysctl mainly because of the fact that the TuneD package (used to tune systems dynamically with specific pre-created system profiles) relies on sysctl parameters.

I found a useful article on sysctl in Linux Journal, which I will post here.

http://www.linuxjournal.com/article/2365?page=0,0

In summary, the /proc folder in Linux is essentially the 'portal' to the kernel parameters. While some are locked down and cannot be tinkered with, others (in /proc/sys) are available for configuration.

This is not for the novices. Understanding the parameters themselves is a daunting task; something that only kernel developers used to understand by being thoroughly familiar with the kernel source code. Playing and tinkering with the parameters can absolutely cripple a system if you don't know what you're doing.

But - it is good to understand the architecture and facilities within Linux. And understanding sysctl; what it is, why it is there and what it is used for - is certainly something important if you're going even remotely consider calling yourself a Linux geek.

TuneD

Recently I had someone 'in the field' make a comment that one of our servers was not optimized to send video.

I reported this comment back to the Principal Engineer, who informed me that he had installed a package called TuneD on the server, which - depending on how it is configured of course - handles the automatic activation of certain "profiles"; each having a set of optimization parameters.

I looked into this. Sure enough, I found 2 directories; /etc/tuned and /usr/lib/tuned.

The /etc/tuned/ directory contains the main, or high level, configuration file (tuned.conf).

In the /usr/lib/tuned directory contains a list of individual system profiles. On the system I looked at, it appeared that the default profiles (provided by the tuned packagers) were included - which is probably a good thing if you then proceed to examine each of these profiles.

Inside /usr/lib/tuned, a file exists for each individual profile. So for example, in a "balanced" profile, if one were to peek inside of it with an editor (it is a text file), one would see a number of sysctl kernel parameters with specific values that get set when that profile is activated.

The tuned package uses a command line administrative tool called "tuned-adm" to get things done. It is quite simple, actually. Arguments include "off" (disable), "list" (list profiles), "active" (show the active profile"), and even "recommended" to show the recommended profile. If the system is not configured to automatically activate a profile, or a particular profile happens to be excluded due to policy, what is recommended might not be what happens to be active!

You can also create or modify profiles with the tuned-adm tool.

A useful link to get acquainted with the tool can be found at:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Power_Management_Guide/tuned-adm.html

Multi-NIC - Multiple Default Routes

I am in the process of studying Multi-NIC; a process by which with two external ISP network adaptors, you can leverage both of those adaptors to distribute traffic in a bandwidth aggregation model.

I came across this article:
https://kindlund.wordpress.com/2007/11/19/configuring-multiple-default-routes-in-linux/

I configured this, and indeed, it seems to work, but need to do more testing with it.