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Convert SSH private key with PuTTY keygen

This tutorial will show you how to convert SSH private key with Putty keygen.
It is silly, but SSH2 private keys do not have standard format. OpenSSH, ssh.com, PuTTY have different formats, and any key generated with one client cannot immediately be used with another.

For example in my tutorial create and use SSH key under linux we have discussed how to create key pair using ssh-keygen tool. My private key was looking like this:

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Create and use SSH key

This tutorial will explain how to create ssh key which you can use to access your Linux /Unix server without entering password, or just because this is securest and more professional way to access any server.

I presume that you have certain knowledge with SSH and unix /linux commands, so I am going directly to the point were we are going to generate ssh key.

Access your server, login as your preferred user and start ‘ssh-keygen’.
There are a lot of options with which you can play, as encryption type, how many bits it will be ‘¦ etc.
In our case we will use the default one just to show you the method. Once you manage to create key pair and it works, you can always go back and create another one.

So, type ‘ssh-keygen’ in the command line and fallow the instructions.

Using FIND command in Linux/Unix

This tutorial is dedicated to the ‘find’ command used in Linux/Unix operating systems.
‘Find’ is really powerful and commonly used command which helps in troubleshooting, finding stuff and as a part of server scripts.

The very common usage, just to find a file name or folder on your server is:

This will find all files or folders on a particular server with STRING included in the name located into the current folder and all the subfolder.

The next one will find string in files into the current folder and all the rest subfolders.

or

just for your information another way to find string in files :

Why I am giving you two or more commands?
Take in mind that the find command may be different on a different Linux and Unix based operating systems, and the syntax may differ.

Let’s see if we want to find all files bigger than 5MB:

Or find files bigger than 10MB using different find syntax :

To find user files you may search by ‘User ID’ into the systems (this may take time!)

To find all files modified in the last 5 minutes‘¦

… and if you want them all deleted:

Let’s find directories with certain permissions:

Here is how to find files with same permissions

or

Find files without associated user:

Find files modified and created last two days:

The next command will show you a list of SUID/SGID of programs in your system.

The next ‘find’ string will show you how many directories, files and links has a particular folder.

Note that if you remove the “-follow” ‘find’ parameter it wont search/ trace symlinks (Symbolic links).

With the following command you can find and replace in all files using ‘sed’, from the current folder recursively for a string (in my example ‘mamma mia!’) and will replace it with another which will be ‘daddy dog’.
(For the special characters you have to use so-called ‘escape’ character )

As it is too complicated you can find and replace with FIND and SED

It is very, very useful, but be careful how you are using it. It is a must to have backup, before messing all around!

With the next string one you can do a change on every ‘.php’ file in this case we are going to change the permissions of all files to 644 found inside the current and all of the subfolders.

Hope you liked the ‘find’ command examples. I am using them very often and even that I am referring to this tutorial for fresh ideas.

Think twice cut ones!

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Debian software selection

This tutorial continues from Partitioning disk – Debian installation and will cover the final steps of Install Debian Linux using graphical install .

We will continue with Debian Software selection as at the moment, only the core of the system is installed. To fit the system as per your needs, you can choose to install one or more of the following predefined collections of software.

The Debian software installation options are:

Desktop environment ‘“ with this package Debian will add all applications needed for fully functional Desktop environment.

Web server – program that, using the client/server model and the World Wide Web”s Hypertext Transfer Protocol ( HTTP ), serves the files that form Web pages to Web users. This will install Apache one of the leading Web server applications.

Print server ‘“ this will add print support

DNS server ‘“ if you want to have custom DNS like ns1.mydomain.com, then this service will be needful

File server ‘“ thjis will provide a location for the shared storage of computer files (such as documents, sound files, photographs, movies, images, databases, etc.) that can be accessed by the workstations that are attached to the computer network.
Mail server

SQL database ‘“ this is a computer program that provides database services to other computer programs or computers, as defined by the client-server model.

Laptop ‘“ includes packages for Laptop power-management and features support.

Standard system ‘“ most of the standard Linux packages that usually.

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Partitioning disk Debian installation

This tutorial continues from Install Debian Linux using graphical install , and will proceed with disk partitioning for the Debain installation.

When you are ready click on ‘Continue’ to proceed with Debian partition disk section. The installer can guide you trough partitioning a disk (using different standard schemes) or, if you prefer, you can do it manually. Using guided partitioning you will still have a chance later to review and customize the results.

If you choose guided partitioning for an entire disk, you will be asked which disk should be used.

The partition methods are:

– Guided ‘“ use entire disk
– Guided ‘“ use entire disk and set up LVM (Logical volume management)
– Guided ‘“ use entire disk and set up encrypted LVM
– Manual

Just for your information: Logical volume management provides a higher-level view of the disk storage on a computer system than the traditional view of disks and partitions. This gives the system administrator much more flexibility in allocating storage to applications and users.

Install Debian Linux using graphical install

This will be a review of an installation of Debian Linux using graphical install. This will be useful in case you are changing Operating systems and just want to see what the install requires.

In general – Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run.
Debian GNU/Linux provides more than a pure OS: it comes with over 25000 packages, precompiled software bundled up in a nice format for easy installation on your machine.

First find a suitable Debian distribution at http://www.debian.org/ . If you have good network connection, you may decide to do Debian network install. Otherwise just choose one of the provided Debian CD ISO images and download it locally. Then burn it with your preferred CD/DVD burning program, and boot from that new media.

You will see the first Debian installation page:

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Pcmcia module viaccess

Pcmcia module viaccess – three words that are used very often in the Internet. Certainly we are talking about digital television, and in this article we will give you directions about how to install a DVB pcmcia device on Linux.

We assume that you already have pcmcia module viaccess plugged in your laptop. By default pcmsi is running on Linux, also the distribution of your OS should be > 2.6 kernel.
If this is so, there is an option to have the needed modules already compiled.

You need to check the specification of your card and to have the drivers coming from the manufacturer. If there are not any provided you will have to use the common ones developed by the Linux geeks over the word.

Lets start because our ‘pcmcia module viaccess’ is waiting.

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Base Linux network settings

Like any other operating system Linux needs adjustment after its installation. One of the largest facilities of the operating system is easily configured through simple text files. These files are located in the directory /etc. This folder contains many files and sub folders, such sub folder pool configuration files status. For example all the scripts, which run and stop processes, respectively the trigger and shut the computer located in sub folder rc.d. Sub folder X11 configuration files then combines the graphic server, etc. This lecture will introduce how you can tune your network settings after the installation of your Linux.

Files that set the network configuration of the operating system are many, but we will check only the important ones:

hosts – file describes the names of computers by connecting them with their IP addresses. Every computer can be taken, short name or nickname. File format is the following:

Disable or enable ping

This tutorial will show you how to disable or enable ping(ICMP) requests on a machine with RedHat like Linux operating systems.

There is a flag that must be changed according to your needs e.g. to disable or enable ”icmp_echo”
That flag must be set at this file:

/proc/sys/net/ipv4/icmp_echo_ignore_all

by default it is enabled as the flag is set to ”0”

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How to disable the direct root login via SSH

This tutorial will show you how to disable the direct root login on a computer with Unix/Linux operating system.

To stop the direct root access you must edit the SSH configuration file located at ”/etc/ssh/sshd_config”

Open the file with your favorite editor, for example VIM, and locate the ”Authentication” section. There set PermitRootLogin to be ”no” as in the example bellow.