Git is a version control system which means that it allows you to keep track of your code or any kind of text throughout the development.

Meaning, you can rewind back and forward to any stage of the code development. Without going into much detail, this is done mainly via few basic commands: clone,
add,commit, push and pull.

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Introduction

For many years people have wanted to protect their right to privacy. As technology changes, it seems that privacy evolves away more and more. I2P is a protocol used for an encrypted multi-proxy on the Internet. While, this sounds simple, there is actually a lot of work going on with I2P to achieve this. Unlike some multi-proxies, I2P will allow you to tunnel many more applications through it than just web browsing, making it a very robust protocol.

I2P is available for all platforms, not just Linux. For this example I have used Debian Sid to perform the installation. With the exception of ‘apt-get’, these instructions should work fine with any Linux distribution. But if you experience problems, please seek documentation for your distro.

Legal Disclaimer

As I explain this to help you maintain priviacy, there will always be a few bad apples in the crowd. I do not condone this use of this article for anything illegal. Even if you are not passing illegal information on I2P, please check your country’s laws on encryption and it’s exportation before you begin.

The Problem with Tor

One would probably see I2P as an overkill without knowing the downfalls of its predecessor. Tor was once a wonderful multi-proxy used for hiding ip addresses and bouncing off servers all over the world. At one time, it was even trusted by most governments for strong anonymity. All of that seemed to change after an article was posted in 2600 Hacker Quartley. One author exposed how becoming an exit node for Tor allowed all the traffic on the Tor network to pass right through your machine. Becoming an exit node was the same as performing a Man-In-The-Middle attack. All one had to do was open up a packet sniffer and see all the traffic going through encrypted. Tor is still used by people trying to protect their privacy. But at the same time it has become a playground for hackers and governments monitoring what they consider suspicious. I2P has secured this problem while adding more functionality.

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As a system administrator or just a backup-conscious home user, sooner or later (usually sooner) you will have to deal with backups. Disasters do happen, ranging from electrical storms to drive failures, and one needs to be prepared. We cannot stress enough the importance of having copies of important data. While the whole concept of backup is too long for this article, we will focus on rsync for what’s called incremental backups.

Incremental backups are based on the idea that, once you have a copy of the data you need to backup, consequent backups of the same data should be incremental, meaning that you only update the backup copy with the differences since the last operation occurred, not create another full copy. We will detail here a setup we have at home for backing up important data, but the examples here can be used at larger facilities. Once you get started, you will know what, where and when you need.

If you have a backup server that’s up 24/7, you can create a cronjob to backup your data periodically. Since our example is home-based, we have a backup server, but since it’s not up all the time, we will show you how to do it manually. rsync needs to be installed on both systems, and that’s about it, no other setup chores must be performed, at least in simple cases. Please remember that you are not by all means tied to Linux or other Unix platform : rsync is available also for Windows. If you are worried about security, rsync is working over SSH and can be regarded as a secure replacement for rcp (remote copy) command, so it’s all good.

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XZ is another compression method used to compress data. There are several ways on how to decompress XZ archive on Linux. For a tarball XZ compressed archive first try a tar command with xf options. This way a tar command will try automatically guess a compression method. Before you run the above command firs install XZ tools:

# apt-get install xz-utils

Otherwise, you will receive error message output:

tar (child): xz: Cannot exec: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now

To extract XZ tarball run:

$ tar xf myarchive.tar.xz

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Objective

The Virtual Machine creation using template provisioner may spawn unnamed VDI disks. Usually, the VID description states Created by template provisioner at most.
Example:

uuid ( RO)                : 093e128a-2632-43bd-bb45-8f864bc69d6f
          name-label ( RW): 0
    name-description ( RW): Created by template provisioner
             sr-uuid ( RO): 3ef7b35b-5d39-7414-0c91-bbb281b9a521
        virtual-size ( RO): 21474836480
            sharable ( RO): false
           read-only ( RO): false

The objective is to set a proper name and description to VDI disk.

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Normal data deletion does not erase all data from SSD as same parts are reserved and omitted by removal process. The function secure erase function allows for a complete data removal from all cells. The secure erase function is offered by SSD manufactures and not all hard drives or Linux kernels support it. In the below examples we will refer to /dev/sda block device as our test drive. To find whether your SSD hard drive supports secure erase run a following linux command:

Warning:

ATA Security Feature Set
These switches are DANGEROUS to experiment with, and might not work with some kernels. USE AT YOUR OWN RISK.

# hdparm -I /dev/sda | grep erase
		supported: enhanced erase

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Introduction

Any decent Linux distribution comes with an installation option to automatically encrypt user’s home directory. In case you do not wish to encrypt the entire home directory or perhaps you wish to encrypt some random directories on your Linux system you can use EncFS the FUSE-based cryptographic filesystem. EncFS will allow you to encrypt and decrypt any directory in a matter of seconds. It will reside on top of your current filesytem and provide access to any EncFS encrypted directory only upon entering a correct predefined password. This short tutorial will show you how to encrypt and decrypt your directories with the EncFS cryptographic filesystem.

Scenario

Let’s assume that you are a heavy Laptop user traveling from one place to another. You also use ssh quite often and so you have generated ssh keypair. For your convenience you even generated a private key without using a pass-phrase ( never good idea ). Furthermore, you have copied you public ssh key to multiple servers for an easy access. The problem with this scenario is that once someone gets hold of your Laptop s/he gets instantly access to all servers using you private ssh key. In this article we will show you how to encrypt your .ssh directory and avoid such problem.

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Objective

The objective is to set a new name label on a existing XenServer’s VM ( virtual machine ).

Requirements

Privileged access to XenServer’s command line as well as configured ISO image storage containing an ISO image of the Linux distribution you wish to install.

Difficulty

EASY

Instructions

Identify VM’s UUID

In order to set/rename VM’s name label we fisrt need to identify its UUID. List all VM’s and take a note of a relevant UUID. Example:

# xe vm-list
uuid ( RO)           : bad8e456-df88-435d-ba12-3f0f6e54b2c6
     name-label ( RW): Control domain on host: xenserver
    power-state ( RO): running


uuid ( RO)           : 699dcb0c-e897-5bd4-30c1-ab1dd9a3ca4e
     name-label ( RW): Debian Jessie 8.0
    power-state ( RO): halted

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