Adam Williamson from happyassasin.net has a nice article titled Some comparisons between Fedora 13, 15, 17, 19 and 20. Adam works for Red Hat as Fedora QA Community Manager, meaning he knows what he’s taking about:
We can see that the memory used when you simply boot to a console and log in has changed very little all the way back to Fedora 13, released 2010-05-25. We’re doing a fairly good job of keeping our base system from bloating excessively. 19 and 20 are both 30MB worse than 17, but then, 17 was 25MB better than 15.
The same certainly doesn’t hold true for the graphical desktop, though. Just sitting at a mostly-idle desktop with a terminal open, our memory usage has gone from 275MB under the ancien GNOME 2 regime to 300MB with GNOME 3′s ‘fallback mode’ (which was more or less GNOME 2), then rocketed to nearly 400MB, 535MB, and nearly 700MB in subsequent releases. I haven’t yet looked in detail at the changes, but I did take screenshots of ‘top’ ordered by memory usage for each install.
The measurements are done using free command in a gnome-terminal immediately after bootup. GNOME runs in a virtual machine without hardware acceleration, and it ends up using Mesa llvmpipe driver. These are the graphs based on Adam’s measurements:
Fedora server memory (MB)
Fedora GNOME Desktop memory (MB)
Ethernet networks can be partitioned into multiple distinct broadcast domains using VLANs. VLAN domains are mutually isolated. Whenever a hosts in one VLAN domain needs to communicate with a hosts in another VLAN domain, the traffic must be routed between the two domains. This is known as inter-VLAN routing.
This document provides a VLAN configuration example for a small network split into two separate VLAN domains: SALES and ENGINEERING. The backbone consists of two VLAN bridges connected by a VLAN trunk. I will use a Linux-based router, RCPlive, connected to the trunk to provide routing between the two VLAN domains and the outside world. On the router I will also enable a number of services such as DHCP and stateful firewall.
Virtualization refers to the creation of virtual machines that acts like real computers with an operating system. Software executed on these virtual machines is separated from the underlying hardware resources.
This article discusses LXC, a lightweight virtualization technology built into Linux kernel. The user space LXC tool is distributed with a number of templates that allow the creation of different Linux distro filesystems, usually one template for each major Linux distribution. The problem with these templates is they never work, or they stop working with every new release of LXC tool or of the particular Linux distribution. This is the case with all Linux distributions, and Debian is no exception. Currently, the Debian template is borken under “wheezy”. The relevant Debian bug is here, and history shows that as soon such a bug gets fixed, lxc user space driver changes again and breaks it. It could be worse, in Fedora LXC was broken in Fedora 15 and it was never fixed.
The simple way to handle the problem is to forget all about the template mechanism and roll your own containers. In Debian you can build the container filesystem using the standard debootstrap, or mount read-only the host filesystem, and then use lxc-execute to start a simple bash session inside the container. In this session you can than start all the programs you need to run in the container. It is an application container, very similar to the containers created using the official ssh template distributed with LXC.
The virtual machine I will describe in this article uses a root filesystem build using debootstrap (apt-get install debootstrap). The procedure is simple and it should work on any Debian machine. It will probably work also on any other distro based on Debian, such as Ubuntu, Mint etc.
Hundreds of new open source software projects are published on Internet each day. The vast majority are built by private individuals in their spare time, or at least this is how the projects are starting. The usefulness of these projects is secondary in nature, most of the time the goal is learning and personal development, or how somebody else put it, scratching one developer’s personal itch.
This blog post is about how to package and publish an open-source project. I have this source code just sitting there on my hard drive, I wrote it some time ago, other people might find it interesting. Let’s start with the itch.
Many people are very surprised when they find out telnet protocol requires more than a TCP socket connection between a client and a server. There are two tty terminals involved, one on the server side, and one on the client side. These terminals are synchronized by special messages sent over the socket connection, mangled with the session data.
To figure it out, I can start by reading a long list of RFCs, or I can take a shortcut and try to lift it from a wireshark trace:
An SNMP MIB browser is an indispensable tool for engineers and system administrators to manage SNMP enabled network devices such as routers, switches, servers and workstations. The information provided by SNMP includes uptime, interface traffic data, routing information, TCP and UDP connection information, installed software, and much more.
In this tutorial, I introduce qtmib, an easy-to-use SNMP browser available for Linux and published under GPLv2 license. The program is build as a front-end for net-snmp tools using QT4 library.
qtmib browser window
A live CD or live DVD is a complete bootable Linux operating system loaded from a CD or DVD. Although there are a lots of live Linux CDs, for seemingly every taste and purpose, it might still be useful on occasion to build your own. This guide details the steps to build a bootable live CD/DVD based on Debian “wheezy”.
Step 1 – Installing the necessary software
These are the software packages you need to install on your Debian system:
# apt-get install xorriso live-build syslinux squashfs-tools
Step 2 – Create a basic filesystem
Start by creating a new work directory, and bring in a basic Debian filesystem using debootstrap. Depending on your network connection, it will take some time downloading all the necessary packages:
# mkdir ~/livework && cd ~/livework
# debootstrap --arch=amd64 wheezy chroot
The new filesystem was created in ~/livework/chroot directory. It is time to chroot into the new filesystem and finish the installation.
Virtualization allows the creation of multiple virtual machines (VM) on top of an existing computer, each VM configured in a very specific way. All virtual machines run in parallel alongside the regular host applications, without affecting the host system. The type of virtualization I am currently using is Linux containers (LXC), a lightweight virtualization technology built into Linux kernel.
This is my third Debian virtualization article. In the first article, I’ve described the steps to create and run a basic virtual machine using LXC. In the second article I’ve isolated the VM on its own network segment, with its own TCP/IP networking stack. Both articles were dealing with server VMs, I’ve used Lighttpd as an example throughout my articles.
I will describe now how to run desktop applications such as Mozilla Firefox and LibreOffice in a virtual machine. I will use virtenv to build and run the VM. virtenv is a QT4 application released under GPLv2 license. It is basically a configuration wizard that allows you to configure and start the LXC-based virtual machines. Once the VM is started, you get a regular controlling terminal (xterm) and a desktop window running the lightweight Openbox window manager. In this window you can run your GUI applications, very similar to VMware Workstation or Oracle’s VirtualBox.
virtenv desktop and controlling terminal