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Showing posts with label linux. Show all posts
Showing posts with label linux. Show all posts

Wednesday, 11 June 2014

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Set or Change User Password in Linux

      How do I set or change Linux system password for any user account?
Both Linux and UNIX use the passwd command to change user password. The passwd is used to update a user’s authentication token (password) stored in shadow file.
The passwd changes passwords for user and group accounts. A normal user may only change the password for his/her own account, the super user (or root) may change the password for any account. The administrator of a group may change the password for the group. passwd also changes account information, such as the full name of the user, user's login shell, or password expiry date and interval.

Task: Set or Change User Password

Type passwd command as follows to change your own password:
$ passwd
Output:
Changing password for vivek
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
The user is first prompted for his/her old password, if one is present. This password is then encrypted and compared against the stored password. The user has only one chance to enter the correct password. The super user is permitted to bypass this step so that forgotten passwords may be changed.
A new password is tested for complexity. As a general guideline, passwords should consist of 6 to 8 characters including one or more from each of following sets:
  1. Lower case alphabetics
  2. Upper case alphabetics
  3. Digits 0 thru 9
  4. Punctuation marks

Task: Change Password For Other User Account

You must login as root user, type the following command to change password for user vivek:
# passwd vivek
Output:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Where,
  • vivek - is username or account name.

Task: Change Group Password

When the -g option is used, the password for the named group is changed. In this example, change password for group sales:
# passwd -g sales
The current group password is not prompted for. The -r option is used with the -g option to remove the current password from the named group. This allows group access to all members. The -R option is used with the -g option to restrict the named group for all users.


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How to install a .deb package from Ubuntu Command Line (Terminal)

Debian (.deb) packages are the packages that are used in Ubuntu. You can install any .deb package in your system. .deb files can generally be installed from your file manager (Nautilus) merely by clicking on them, since file associations with the default installer is already set in Ubuntu. These instructions are for those who wish to install packages from the command-line terminal (Terminal).

To install a downloaded Debian (Ubuntu) package (.deb): Open Terminal and type

sudo dpkg -i packagename.deb

To remove a Debian (Ubuntu) package (.deb):

sudo dpkg -r packagename

To Reconfigure/Repair an installed Debian (Ubuntu) package (.deb):

sudo dpkg-reconfigure packagename
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Install RPM Packages on Ubuntu/Linux Mint

        Ubuntu/Mint Support only deb package installation, If you have some software in rpm package you can install it in Ubuntu/Linux Mint easily. Fedora/Redhat and Mandriva support RPM packages.
In Ubuntu/Linux Mint you can easily install softwares from Software Centers or via PPA. If any software is not available in deb/software center/ppa and it's only available in rpm, than you can easily convert that rpm file to deb package with one command using terminal.

This RPM to DEB Conversion Utility called Alien, Which converts packages from one to the other format. It doesn't mean that convert rpm package will always work on your system. Cause there can be problem of Dependencies or libraries.

To install open Terminal (Press Ctrl+Alt+T) and copy the following command in the Terminal:




Now convert package from RPM format to Deb format, use the following command. Change your packagename in command:



To install the deb package enter following command:



That't it 


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How to Use Linux:Problems You'll Face Using Linux Offline


Using Linux Operating System can be a real headache for early beginners when they are not connected to Internet. So I am writing this article covering major problems faced when one has to install software on an offline Linux machine and solutions to them.
When I first met Linux, thing I was screaming for was, where to find the setups of software. As I used to do in Windows, downloading and saving software setups for future installs is quite handy than downloading it every time. But it is hard to do this in Linux for a number of reasons.

Many so called user-friendly Linux Distributions like Ubuntu come without software people (new to Linux) expect preinstalled e.g. Ubuntu come without mp3 plugins and other codecs. So when offline, it is really irritating when one can’t even play his/her favorite music. These include a large number of files which are hard to fetch manually.
Most software are available as source-codes packages on their websites to download and not in binaries. 
Even when it is possible to download .deb/.rpm packages and install them, as Linux uses a shared library system, most packages have lots of dependencies which have to be built and installed before main software. Downloading and building all the dependencies and main software in right order can be a real headache at times.
Source codes are tough to compile for novices and if even they can compile, uninstalled dependencies come in the way.


How to install software on an Offline Linux machine:


Solutions here are focused on Debian based Linux Operating Systems like Ubuntu and other Debian/Ubuntu derivatives.

The main idea is to install or download software on a machine connected to internet and then somehow carry them to the offline computer. Package managers of GNU/Linux distributions like apt-get do a very nice job of downloading and installing software ’with’ their dependencies, and we are going to use their power for our purpose (installing software on offline Linux machine).

Manually copying software installed using apt-get: Software installed on a system through apt-get, aptitude or synaptic etc are saved on hard disk. This method involve manually copy them and installing them on offline machine. However this method is not recommended for novices.
⇒  Install software on Linux system connected to Internet.
⇒ Copy software from apt archives ( var/cache/apt/archives ) to usb drive etc.
⇒ Carry software on offline machine and paste them there.
⇒ Install software using packet managers ( Synaptic recommended).
Using Aptoncd: Aptoncd is a software developed for automating above stated process of backing up software downloaded and installed  using apt-get, and it do this job very well. It is a very nice software with nice GUI interface and easy to use for beginners.
⇒ Open Aptoncd
⇒ Create iso image of apt archives directory
⇒ Burn it to CD/DVD
⇒ Restore to offline computer
⇒Install all packages using one command
           sudo dpkg -i /var/cache/apt/archieves/*.deb
   
Using Keryx: Keryx is a portable, cross platform offline package manager for Debian based Linux distributions (Ubuntu and derivatives). It works on a different principle. Keryx Download software on computer connected to internet (it may be on Linux or Windows) and then install them to offline PC.
⇒ Extract Keryx to a USB drive
⇒ First run Keryx on the offline Linux machine where it make a profile about the Linux  Distribution and software installed on it.
⇒ Then run it on Computer with Internet connection (it may be Windows or Linux) where you  can select and download software.
This method is highly recommended for novices/ beginners as it involve very little manual work. Read complete Keryx tutorial here.
Using Remastersys\Create Custom Live disk: This is my favorite method for backups as I frequently reinstall my Operating System(s) ( I have my reasons). This method involve using a script called Remastersys for making a bootable disk from a system already installed with Debian/Ubuntu/derivatives. In this process all the software installed on the machine also get included in the disk prepared with Remastersys. This is a brilliant method highly recommended for novices.
⇒ Run Remastersys GUI
⇒ Follow the instructions (choose dist option)
⇒ Copy iso image of your custom Live CD/DVD from /usr/home/remastersys/remastersys
⇒ Burn it to disk or make a live USB using Unetbootin
⇒ Install newly born custom Linux Distribution to offline PC 
But as with everything in life, all solutions have their own cons, pros and side effects. It is recommended to read each their tutorials (follow given links) for details.
If I am missing something here, or something I have written wrong, suggestions are more than welcome.



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