Taglinux

How to enable telnet in a Linux server?

Telnet is a network protocol, used to provide bi-directional text-oriented communication facility.

Note: Telnet in is insecure protocol and it is recommended that you use ssh server. 

WARNING! Installing telnet on your server makes the server open to an un-encrytpted communications, it’s not recommended to use telnet, use Secure (SSH).

Telnet Server installation

In Debian/Ubuntu
user@techinx$ sudoapt-get install telnetd
In fedora/RedHat
root@techinx# yum install telnet-server telnet xinetd

Configure telnet server (turn on telnet server)

If you are using Red Hat / Fedora Linux
The configuration file for telnet is /etc/xinetd.d/telnet. To enable telnet server you need to open this file and make sure disable = no read as disable = yes.
Alternately,
root@techinx# chkconfig telnet on
To start telnet server type command:
root@techinx# /etc/init.d/xinetd restart

How to enable root login from telnet server

Edit /etc/securetty file, In the end of file add pts/0 to enable one telnet session for root. if you need to open more telnet session for root and add more pts/1 pts/2 and so on.

Restart services, you are done!.

Unable to install IBM Installation Manager on RHEL 6.* (64-bit)

There was an issue, with IBM installation manager not able to install or start in RHEL 6.* series. This issue is fixed by IBM and is available in Fix central for download. The fix name is agent.installer.linux.gtk.x86_64_1.6.0.20120831_1216.

If you are using the old IBM installation manager, during install you may face errors like this.

[root@rhel64]# ./install
bash: ./install: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory

Cause:

Installation Manager is a 32-bit application and requires 32-bit versions of OS system libraries. These libraries are not installed on RHEL 6.0/6.1 x86_64 (64-bit) by default. You must install these 32-bit libraries on your system before you run Installation Manager.

Solution:

Configure yum on your server, install the required 32bit binaries.

To configure yum on your server refer here http://www.technix.in/local-yum-setup-for-rhel/

after the yum configuration install the dependent 32bit binaries as shown below.

[root@localhost]# yum install gtk2.i686
[root@localhost]# yum install libXtst.i686
[root@localhost]# yum install compat-libstdc++

Once the install is complete. IBM installation manager installation can be proceeded as normal.

 

How to use proxy server from Linux terminal

In Linux/Unix there is an environment variable called “http_proxy” which can be configured for text based internet sessions.  This variable is used by wget, curl, lynx etc.

How to set http_proxy variable

Type the following command to set proxy server

#export http_proxy=http://10.99.2.197:8080

 How to set the http_proxy variable globally

#vi /etc/profile

add the following lines.

#export http_proxy=http://10.99.2.197:8080

 How to I use a password protected proxy while using command line internet

#curl --proxy-user <username>:<password> www.technix.in

 

 

What’s a cron and crontab?

Cron is a a time-based job scheduler in Unix/Linux environments. Cron can be used to schedule jobs to run periodically at fixed times, dates or intervals.  Crontab is a configuration file that specifies  shell  commands to run periodically on a given schedule.

Users can have their own individual crontab files and often there is a system wide crontab file (usually in /etc or a subdirectory of /etc) that only system administrators can edit.

Crontab format

MIN  HOUR DOM MON DOW <command to execute>

  1. MIN =Minute(0-59)
  2. HOUR =HOUR(0-23)
  3. DOM =Day Of Month(1-31)
  4. MON =Month(1-12)
  5. DOW =Day Of Week(0-6)

cron

How to view crontab entries?

To view current user’s crontab, use “crontab -l

eg :

cron1

 

 

To view other user’s crontab, login as root and give “crontab -u sam -l

cron2

 

 

How do I edit crontab entries?

We can issue “crontab -e”  for adding or editing crontab entries.

 

How do I rebuild grub after Windows 8 installation

Recently I had updated my System which was dual booted (Debian and Windows 7) from Windows 7 to Windows 8, During the installation process I had messed up with Grub boot loader. Once after the upgrade my Grub has vanished and I was able to boot up only Windows 8.

A bit disappointed thinking about windows Not giving an option to Select a boot loader of my choice, I started looking back on my System admin skills and finally here’s how I recovered my Boot loader.

1. Boot from a CD or Live USB.

2. Go to Linux rescue.

3. Get the partition tables for the hard disk devices using fdisk command, and find out the linux root file system, in mycase it was /dev/sda6

# fdisk -l

4.  mount the root filesystem using the mount command.

#mkdir       /recover

#mount     /dev/sda6        /recover

5. mount /proc and /dev filesystems

#mount    -t     proc     none       /recover/proc

#mount    -o    bind      /dev      /recover/dev

7. Now chroot to the mounted root filesystem

#chroot     /recover

8. Now do grub-install to reinstall grub

#grub-install  /dev/sda

9. Grub-install finished without error  and I was able to dual boot from Grub after a Reboot.

 

Here comes Ubuntu 13.10!

Ubuntu 13.10 Code named “Saucy Salamander” is released for the desktop, server, phone, and cloud – download it here.

Ubuntu 13.10 introduces the first release of Ubuntu for phones and Ubuntu Core for the new 64-bit ARM systems (the “arm64” architecture, also known as AArch64 or ARMv8), and improved AppArmor confinement. In addition to these flagship features there are also major updates throughout.

Ubuntu Server 13.10 includes the Havana release of OpenStack, alongside deployment and management tools that save devops teams time when deploying distributed applications – whether on private clouds, public clouds, x86 or ARM servers, or on developer laptops. Several key server technologies, from MAAS to Ceph, have been updated to new upstream versions with a variety of new features.

Maintenance updates will be provided for Ubuntu 13.10 for 9 months, through July 2014

Users of Ubuntu 13.04 will be offered an automatic upgrade to 13.10 via Update Manager. For further information about upgrading, see:

http://www.ubuntu.com/download/desktop/upgrade

 

For release notes visit here

KDE Releases Beta of Plasma Workspaces, Applications and Platform 4.11

Today KDE released the beta of the new 4.11 versions of Workspaces, Applications, and Development Platform. With API, dependency and feature freezes in place, the KDE team’s focus is now on fixing bugs and further polishing.


Changes to KWalletManager and Okular

The 4.11 releases include many substantial changes and improvements, including:

  • Deeper integration of Qt Quick in Plasma Workspaces
  • Faster Nepomuk indexing; massive performance optimizations, such as reading data is 6 or more times faster than previously
  • Kontact improvements—faster indexing, new theme editor, a lot of bug fixes
  • KWin—many OpenGL improvements, work on an OpenGL 3.1 core context and improved robustness, optimizations aimed at reducing CPU and memory overhead

More improvements can be found in the 4.11 Feature Plan.

With the large number of changes, the 4.11 releases need a thorough testing in order to maintain and improve the quality and user experience. Actual users are critical to maintaining high KDE quality, because developers simply cannot test every possible configuration. We’re counting on you to help find bugs early so they can be squashed before the final release. Please consider joining the 4.11 team by installing the beta and reporting any bugs.

Red Hat Software Collections 1.0 Beta Now Available

Red Hat announced the beta release of the Red Hat software collection 1.0. Red Hat Software collections 1.0 delivers the latest stable versions of some of the most popular web development languages and opensource databases.

redhatRed Hat Software Collections 1.0 Beta includes access to the latest stable versions of the following dynamic languages:

  • Ruby 1.9.3 with Rails 3.2.8, which delivers substantial performance improvements for web-based applications. This results in faster load times, improved unicode support and threading, and a large collection of ruby gems.
  • Python version 2.7, which includes new unit test features, faster I/O, and tools and back-ported features from Python 3 to make future migration easier.
  • Python version 3.3, which offers significant improvements in language consistency, Unicode performance, imports, and distribution of packages.
  • PHP version 5.4, which includes new language syntax, improved performance and reduced memory consumption, and a built-in web server in CLI mode to simplify development workflows and testing.
  • Perl version 5.16.3, which includes improved unicode support, performance enhancements, new debugging options, enhanced security, and a number of new and updated modules.
  • Technology Preview of node.js version 0.10, which delivers an easy to use module for handling streams, better error handling with domains, and performance improvements for web application development.

Red Hat Software Collections 1.0 Beta also includes access to the latest stable versions of the following runtime databases:

  • MariaDB version 5.5, which introduces an easy-to-adopt alternative for MySQL for Red Hat Enterprise Linux users. Binary compatibility allows MySQL users to drop-in MariaDB without converting data files.
  • MySQL version 5.5, which offers performance, scalability, and usability enhancements.
  • PostgreSQL version 9.2, which includes native JSON support, covering indexes, and significant improvements in replication, high availability and performance.

Red Hat Software Collections 1.0 Beta is available now for use with Red Hat Enterprise Linux 6 to customers and partners with select active Red Hat Enterprise Linux Server, Red Hat Enterprise Linux Workstation or developer-related subscriptions.

Local Yum Setup for RHEL

The Yellowdog Updater, Modfied (YUM) is an Open-source command line package-management utility for RPM based Linux systems. YUM allows automatic updates, package and dependency management.

This article helps you in YUM setup in RHEL enviroments

1. Create RPM directory

root@technix#mkdir /RPMS

2. Copy all the rpm packages from disk to “/RPMS" directory

3. Install createrepo rpm

root@technix#rpm -ivh createrepo-0.4.11-3.el5.noarch.rpm

4. createrepo

root@technix# createrepo /RPMS

5. create a local repo file in /etc/yum.repos.d

root@technix#vi /etc/yum.repos.d/local.repo

& save the below lines

[local]
name=RHEL-$releasever - Local
baseurl=file:///RPMS/
gpgcheck=0
enabled=1

6. Make yum Cache, by executing

root@technix#yum makecache

Enjoy software updates locally.

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