Install iftop, htop and NetHogs on RHEL / CentOS 6.x x86_64 [Internet Required]

Recently I was given a task to create two CentOS 6.5 Jump Servers in the environment I am working currently.

There was a specific requirement for the following packages.

  • iftop – Network Bandwidth Monitoring
  • htop – Linux Process Monitoring
  • NetHogs – Monitor per process Network Bandwidth

We have an internal secure proxy server via which Internet was easily available for my servers. This is how I did:

Step 1 – Enable EPEL (Extra Packages for Enterprise Linux) and install rpm

cd /tmp

wget http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

rpm -ivh epel-release-6-8.noarch.rpm

Step 2 – Verify EPEL Repo

yum repolist

(it should display EPEL repo in the output)

Step 3 – Install packages

yum -y install iftop

yum -y install htop

yum – y install NetHogs

Note: Just in case you face the following error:

yum error “Cannot retrieve metalink for repository: epel. Please verify its path and try again”

You will have to edit the following repo’s by commenting entries ‘mirrorlist=..’ and un-comment entries ‘baseurl=…’

  • /etc/yum.repos.d/epel.repo
  • /etc/yum.repos.d/epel-testing.repo

HowTo configure Telnet on Linux (Redhat)

Telnet
Telnet

Re-blogged from Zahidhaseeb’s Blog:

In my environment I have used Linux Redhat 6.2

  • Install three packages telnet-server, telnet and xinetd.
  • Make sure that the xinetd service should be running.
  • Configure the file name /etc/xinetd/telnet

1.) Install three packages telnet-server, telnet and xinetd.

You need to install three services

for example # yum install telnet-server telnet
the above command will also install the xinetd service. See the following example for reference:

Dependencies Resolved

=====================================================
Package               Arch         Version                  Repository    Size
=====================================================
Installing:
telnet                i686         1:0.17-47.el6            base          56 k
telnet-server         i686         1:0.17-47.el6            base          36 k
Installing for dependencies:
xinetd                i686         2:2.3.14-33.el6          base         121 k

Transaction Summary
=====================================================
Install       3 Package(s)

Total download size: 213 k
Installed size: 409 k

2.) Make sure that the xinetd service should be running.

# service xinetd status
xinetd (pid  13561) is running…

Please also note: Make sure that your firewall also stopped or the telnet traffic is allowed

3.) Configure the file name /etc/xinetd.d/telnet

We need to change the following highlighted line from yes to no

# vi /etc/xinetd.d/telnet
# default: on
# description: The telnet server serves telnet sessions; it uses \
#    unencrypted username/password pairs for authentication.
service telnet
{
flags        = REUSE
socket_type    = stream
wait        = no
user        = root
server        = /usr/sbin/in.telnetd
log_on_failure    += USERID
disable        = yes
}

Note:

In few scenarios, telnet works over the ip, but does not resolve specific ports. In that case xinetd services needs a restart

“service xinetd restart”

Some Linux Definition

Linux
Linux

Some basic definition which I wanted to remember always, in my early stages, whereas which is very important to understand if someone will like to learn Unix / Linux with basic concepts rather then just a knowing.

  1. Kernel – It is the core of the system. It controls all the tasks, schedules all the process and carries out all the functions of the operating system. It is the code that controls the interface between user programs and hardware devices. Please always remember it is not an operating system.
  2. Shell – It is the command interpreter of the operating system. It accepts commands from the user and analyzes and interprets these commands. Hence shell acts as a middle man between the Kernel and the users of operating system.
  3. Command – It is a instruction given by a user telling a computer to do something, such as to run a program.
  4. Program – It is an executable file usually files that are stored in one of the bin directory.

Have figured out these definitions from numerous areas.  Share more if you feel like to include in the list.