Bhutan Horizon » Linux

Create User With Full Name in Linux

younten — Tue, 25 Oct 2011 13:44:06 +0000

If you want to add a user along with his/her full name. Here is how to do it.

useradd -s /sbin/nologin -c “Younten Jamtsho” younten

With the above command, I am creating a user younten, who’s full name is Younten Jamtsho. Addition to that, I am assigning nologin shell to the user younten so that he cannot log in to ssh.

Now that you have created the user, use finger command to see the details of the user.

finger younten

IPTABLE Linux Firewall

younten — Sun, 15 May 2011 06:04:18 +0000

Linux have its own firewall package named iptables. iptables are installed by default. iptables file is located in /etc/sysconfig/iptables. Unfortunately, the /etc/sysconfig/iptables file doesn’t support the loading of modules, so you’ll have to add the statements to your /etc/rc.local file which is run at the end of every reboot. Now lets check what modules are being loaded for iptables:

lsmod | grep ip_tables

Now lets add module for iptables.

vi /etc/rc.local

# Module to track the state of connections
modprobe ip_conntrack

Download my iptables file. In this iptables file i have added so many features. Freely use it and secure your network. After downloading rename the file. as iptables only. That mean you have to remove “.txt” from the file name iptables.txt

Install Clamav Antivirus

younten — Tue, 26 Apr 2011 07:27:05 +0000

Before you start installing Clamav Antivirus in your Linux box, please add the extra repository for yum. Install Dag repository, and how to install, go to my post Add Repository for yum.

yum – -enablerepo=dag install clamav -y

After installing there is few changed needed in configuration file.

vim /etc/freshclam.conf
#locate the line below and comment it
#NotifyClamd /etc/clamd.conf

Now update the clamd and its virus defination
#freshclam

To scan for Virus
#clamscan – -infected – -remove – -recursive

eg.
#clamscan – -infected – -remove – -recursive /home

chown

younten — Mon, 25 Apr 2011 09:47:11 +0000

chown stands for Change Ownership.
To change the ownership and group of files and directories

Change ownership of a single file

chown :

eg.
chown root:root message.txt

Change ownership of a directory and all sub files and directories

chown -R :

eg.
chown -R root:root photo

Fail2ban – Block attacks

younten — Sun, 17 Apr 2011 04:43:39 +0000

Your server is venerable to attacks, and you have to time and again monitor. After monitoring you have to block the attackers IP’s. Use Fail2ban package, which would ease you a bit. To install Fail2ban you need to add extra 3rd party repositories – Extra Package for Enterprise Linux (EPEL). After that you can use yum to install the package.

How to install addition repositories for your linux box (Add Repository)

yum install fail2ban

Add repositories for yum

younten — Sun, 17 Apr 2011 04:38:31 +0000

Add Dag RPM Repository for yum because that has many useful packages.

wget http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt
rpm – -import RPM-GPG-KEY.dag.txt
rm -f RPM-GPG-KEY.dag.txt
vim /etc/yum.repos.d/dag.repo

# create new file like below
[dag]
name=Dag RPM Repository for Red Hat Enterprise Linux
baseurl=http://apt.sw.be/redhat/el5/en/$basearch/dag/
gpgcheck=1
enabled=0

When you use DAG repository, Input yum command like below.

yum – -enablerepo=dag install [package]

Add repository Extra Package for Enterprise Linux (EPEL) that is provided from Fedora project.

wget http://download.fedora.redhat.com/pub/epel/RPM-GPG-KEY-EPEL
rpm – -import RPM-GPG-KEY-EPEL
rm -f RPM-GPG-KEY-EPEL
vim /etc/yum.repos.d/epel.repo

# create new file like below
[epel]
name=EPEL RPM Repository for Red Hat Enterprise Linux
baseurl=http://download.fedora.redhat.com/pub/epel/$releasever/$basearch/
gpgcheck=1
enabled=0

When you use EPEL repository, Input yum command like below.

yum – -enablerepo=epel install [package]

Add Remi Collent Repository

wget http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-5.rpm
rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm

When you use Remi repository, Input yum command like below

yum – -enablerepo=remi install [package]

DHCP Server

younten — Wed, 13 Apr 2011 13:59:33 +0000

Set DHCP ( Dynamic Host Configuration Protocol ) Server in Linux Box.

Lets first install DHCP package in
1. yum -y install dhcp

Now that you have installed the dhcp package in your linux box, lets start configuring it.

2. cp /usr/share/doc/dhcp*/dhcpd.conf.sample /etc/dhcpd.conf

3. vim /etc/dhcpd.conf

#line 4: specify your network and subnet

subnet 192.168.0.0 netmask 255.255.255.0 {

# line 7 : specify default gateway
option routers192.168.0.1;

# line 8: specify subnetmask
option subnet-mask255.255.255.0;

# line 10: specify NIS domain name if you are using.
# make it comment if you don not use.
option nis-domain “bhutanhorizon.com”;

# line 11: specify domain name
option domain-name “bhutanhorizon.com”;

# line 12: specify IP address of DNS
option domain-name-servers 192.168.0.10;

# line 14: make it comment
# option time-offset-18000;

# line 21: specify the range of IP addresses for clients
range dynamic-bootp 192.168.0.128 192.168.0.254;

# line 22: default’s terms of lease
default-lease-time 21600;

# line 23: maximun terms of lease
max-lease-time 43200;

# line 26: make following lines comment
#host ns {
#next-server marvin.redhat.com;
#hardware ethernet 12:34:56:78:AB:CD;
#fixed-address 207.175.42.254;
#}

4. Now you have configured the DHCP server. Now you need to start the service named dhcpd

service dhcpd start

5. Now you have to make the service start when ever the linux box starts/reboot

chkconfig dhcpd on

That’s it! you see how easy it is to configure DHCP in linux box compare to Windows Server OS.

Yum to access through Proxy Server

younten — Sat, 08 Jan 2011 05:11:18 +0000

In some network where you have to enter the IP Address of the proxy server to access the internet and you are not able to use the yum command to update your system. You normally put the Proxy Server IP and Ports in your browser setting, but in Linux box that doesnot solve the problem. You need to edit the file /etc/yum.conf, and make a new entry in the bottom of the file as below:

proxy=http://:

Now run the yum command and you will see its now working.

Broadband Connection setup in Fedora 14

younten — Fri, 07 Jan 2011 13:20:51 +0000

I just installed Fedora 14 in my Laptop, after that I wanted to setup a Druknet broadband connection to access internet. After so much of trying i finally did it. My Current Situation of broadband connection was:

Connecting to druknet Broadband through my home wireless network.

1. I connected to my wireless network
2. I went to System > Administration > Network
3. Clicked New
4. Select xDSL Connection from the Device Type
5. Provider Name: broadband
Account Type: Normal
Login Name: dnetXXXXXXXX
Password: XXXXXXXXXXXXXXX
6. Apply
7. I edited /etc/sysconfig/network-scripts/ifcfg-broadband, the line that had ETH to below
ETH:wlan0
8. System > Administration > Network. Then Select the current xDSL broadband connection and Activate it.

Yahoooo, now you are connected to internet!

Problem accessing through FTP Client

younten — Thu, 06 Jan 2011 09:10:32 +0000

There are times when you come across an error message when you use FTP Client, the error message with be something like Failed to list directory or something like that. During such error make sure your Linux server has port 20 and 21 opened in IPTABLES. If those ports are allowed in your IPTABLES than make sure “ip_conntrack_ftp” module is loaded. Check in /etc/sysconfig/iptables-config if the following line exist:
IPTABLES_MODULES=”ip_conntrack_ftp”

If it doesn’t contain then add it or load it in module of kernal.

Loading module for Kernal using rc.local file.

# File: /etc/rc.local

# Module to track the state of connections
modprobe ip_conntrack

# Load the iptables active FTP module, requires ip_conntrack
modprobe ip_conntrack_ftp

# Load iptables NAT module when required
modprobe iptable_nat

# Module required for active an FTP server using NAT
modprobe ip_nat_ftp