March 12, 2013
by Lubos Rendek
Whether you are administrating a small home network or an enterprise network for a large company the data storage is always a concern. It can be in terms of lack of disk space or inefficient backup solution. In both cases GlusterFS can be the right tool to fix your problem as it allows you to scale your resources horizontally as well as vertically. In this guide we will configure the distributed and replicated/mirror data storage. As the name suggests a GlusterFS's distributed storage mode will allow you to evenly redistribute your data across multiple network nodes, while a replicated mode will make sure that all your data are mirrored across all network nodes.
What is GlusterFS
After reading the introduction you should have already a fair idea what GlusterFS is. You can think of it as an aggregation service for all your empty disk space across your whole network. It connects all nodes with GlusterFS installation over TCP or RDMA creating a single storage resource combining all available disk space into a single storage volume ( distributed mode ) or uses the maximum of available disk space on all notes to mirror your data ( replicated mode ). Therefore, each volume consist of multiple nodes, which in GlusterFS terminology are called bricks.
Although GlusterFS can by installed and used on any Linux distribution, this article will primarily use Ubuntu Linux. However, you should be able to use this guide on any Linux Distribution like RedHat, Fedora, SuSe, etc. The only part which will be different will be the GlusterFS installation process.
Furthermore, this guide will use 3 example hostnames:
- storage.server1 - GlusterFS storage server
- storage.server2 - GlusterFS storage server
- storage.client - GlusterFS storage client
Use DNS server or /etc/hosts file to define your hostnames and adjust your scenario to this guide.
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Steganography is the art of hiding messages within other messages or data. Most commonly we see this utilized with pictures. This is probably encryption at its finest.
Mostly because it doesn't look like usual garbled text that we are used to seeing with encryption. The changes made by Steganography are so slight the human eye cannot perceive them. Even trained cryptographers may have an encoded message inside a picture and be unaware of it. There is a very deep science to this. Usually this is done by flipping parity bits at the binary level. While it is great to learn how this works, sometimes it can be a very tedious job. Fortunately for us there is a tool that will take away most of the grunt work.
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This article describes an installation of SysAid software on a Linux system using tomcat and Apache. SysAid is a commercial web-based help desk software and if you were thinking to install either its free or paid version in your organization this guide should help you to achieve it. The default installation of SysAid IT help desk is quite very straight forward. On top of this basic installation this guide will provide you with some extra settings on how to configure SysAid with apache's https service using AJP proxy.
At first, we will perform basic Sysaid ROOT context installation using tomcat. After that we will combine this default Sysaid installation with mysql database and apache2 on port 80. Next we will create a self-signed SSL certificate and deploy sysaid to be accessible via HTTPS URL on port 443.
Here are listed basic environment attributes used in this guide:
- operating system Debian 6.0
- mysql 5.1, apache 2.2, tomcat 6
- example installation URL helpdesk.linuxcareer.com
The following command will fetch all prerequisites for a Sysaid installation on Debian Linux server. Please alter below packages to fit your RPM Linux system such as Fedora, Redhat, Suse and etc.
# apt-get install apache2 tomcat6 mysql-server sun-java6-jre
Debian users only:
If you get a message "Package 'sun-java6-jre' has no installation candidate" make sure to add non-free debian repository into your /etc/apt/sources.list. The following 2 lines below should do the trick:
# sed -i 's/main/main non-free/g' /etc/apt/sources.list
# apt-get update
Set default Java environment
It is possible that your system is running a OpenJDK java environment. Feel free to test this installation using your free OpenJDK java version or set the default java environment to Sun's Java(TM) SE Runtime Environment with:
# update-java-alternatives -s java-6-sun
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This article will deal with installation and configuration of WebDAV server on Ubuntu Linux. WebDAV stands for Web Distributed Authoring and Versioning and allows connected users the edit and share data online via the HTTP protocol. This makes WebDAV a popular choice for developers when combined, for example, with Subversion or OpenLink Virtuoso. WebDAV is supported by number of clients ranging from davfs2, which makes it possible to mount the WebDAV's data storage to include into the local filesystem. This can be done with the mount command to various GUI applications with the native WebDAV support such as Nautilus, konqueror, etc. Futhermore, in this guide we will combine WebDAV with the Apache2 server.
In this section I would like to describe a scenario used in this tutorial. WebDAV can be very flexible service, which allows for number of configuration settings and scenarios. In this WebDAV tutorial we will start with the simplest basic startup WedDAV configuration and from there we will build it up to fit more complex environment. You can think of WebDAV as a HTTP extension for your existing website configuration. Normally, you may already have your apache website up and running. Thus, in that case, all you need to do to in order to include the WevbDAV service is to:
- create additional upload data directory to use by WebDAV
- configure your existing apache2 virtual host file
However, in this guide we will start from scratch starting from apache2 installation, virtual host creation, etc. Therefore, feel free to skip to any section most appropriate to your configuration requirement.
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Introduction and concepts
Every system administrator I know develops in time the habit of putting together a toolbox where, as time passes, many useful pieces of software get added up, as the recurrent need arises. Please do not imagine this in the most classical of the sense, as this is not about a carpenter's toolkit, nor a mechanic's toolbox. It usually is a CD portfolio with live CDs, installable most-used distributions, vendor-specific tools and whatever not. Of the (indispensable) live CDs, one usually sees in the aforementioned toolbox a disk cloning item. What does it do? It helps a tremendous amount when you need to save and restore a hard disk, operating system included, and by save I mean 1/1 copy with the possibility of restoring in a few minutes, despite the ever-increasing size of the hard drives offered by the market today, where the terabyte becomes more and more common.
Such software exists, and indeed it makes the lives of admins and users alike much easier and efficient. Unfortunately, companies tried to impose their own proprietary disk image formats, so that restoring could be possible only by using their tools. Fortunately, there is a FOSS solution that deals with this, offering a very efficient live CD and server for download, and that is Clonezilla, which we'll talk about today. You are expected to have some knowledge on how disks work, networking and system administration. We will treat more advanced subjects a bit later on, but all you need to know if you are a beginner in those matters is right here.
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