How to configure a Linux PPTP VPN client

Last Updated on Sunday, 27 November 2011 01:58 Written by A.Jesin Sunday, 27 November 2011 01:58

Configuring a VPN client connection is a simple matter of point and click in Windows OSes, but in Linux it is involves installing a package, configuring passwords, VPN server settings and finally routing the traffic destined for the VPN network via the VPN connection. The package named pptp is used on the client side for configuring a connection. To setup a VPN server read How to setup a VPN Server in Windows Server 2008. This tutorial is for both Debian Linux variants and Red Hat Linux variants. Read More…

How to setup an unmanaged Debian server

Last Updated on Tuesday, 1 November 2011 10:17 Written by A.Jesin Sunday, 30 October 2011 10:42

So you’ve bought a shiny new VPS or dedicated unmanaged server to cut costs on hosting but don’t know how to begin ? Read this post to make this easirer.  This tutorial will cover the instructions for a basic setup of a Debian unmanaged VPS or dedicated server. The following are covered in this article

• Configuring the Timezone
• Selecting locales
• Creating a sudo user
• Securing SSH
• Adding firewall rules

The first task is to update the apt database and check if any installed packages can be upgraded.

apt-get update && apt-get upgrade

Read More…

How to use MSMTP with Gmail, Yahoo and PHP Mail

Last Updated on Monday, 24 October 2011 09:26 Written by A.Jesin Monday, 24 October 2011 09:26

This is a three in one tutorial which combines how to use MSMTP to send mails via Gmail and Yahoo servers and how to use MSMTP with PHP Mail() function instead of the default sendmail.

Installing msmtp

To install msmtp on Red Hat/CentOS/Fedora type of distributions

yum install msmtp

To install msmtp on Debian/Ubuntu type of distributions

apt-get install msmtp

Configuring msmtp with Gmail and Yahoo

Create or edit the msmtp configuration file in the user’s home directory. I use VI editor to achieve this

vi ~/.msmtprc

Add the following lines to the file, it configures msmtp for both Gmail and Yahoo

account yahoo
tls on
tls_starttls off
auth on
host smtp.mail.yahoo.com
user user1
from user1@yahoo.com
password ******

account gmail
tls on
auth on
host smtp.gmail.com
port 587
user user1@gmail.com
from user1@gmail.com
password ******

Since the file contains sensitive data like passwords you should assign secure permissions

chmod 600 ~/.msmtprc
Read More…

How to save IPtables rules in Debian

Last Updated on Saturday, 22 October 2011 06:44 Written by A.Jesin Saturday, 22 October 2011 02:15

This article explains how to make IPtables firewall rules sustain a boot in Debian. But this can also be applied on other Debian based OSes like Ubuntu and Knoppix. You show execute all these commands as the root user or use the sudo command to do it.

First view the list of rules in IPtables

iptables -L

If its a new installation there will be no rules. So add some firewall rules, the following rules will allow HTTP, HTTPS, FTP, SMTP, SSH incoming connections and rejects all other incoming connections including ICMP ping packets.

iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 443 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 21 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 25 -j ACCEPT
iptables -A INPUT -m state --state NEW -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -j REJECT

View the firewall rules once more

iptables -L

Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED
ACCEPT     all  --  anywhere             anywhere
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:www
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ftp
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:smtp
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp dpt:ssh
REJECT     all  --  anywhere             anywhere            reject-with icmp-port-unreachable

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Write these rules to a file using the following command.

iptables-save > /etc/iptables.rules

Now each time Debian boots iptables-restore command has to be called with these rules, so create and edit a new file as shown below. This file does NOT exist and you have to create it. I’m using VI editor to edit it

vi /etc/network/if-pre-up.d/firewall

Add the following text to that file

#!/bin/bash
/sbin/iptables-restore < /etc/iptables.rules

Save the file and grant executable permissions on that file.

chmod +x /etc/network/if-pre-up.d/firewall

Reboot the system and list the iptables rules to check if it has been applied.

reboot

After reboot

iptables -L

IMPORTANT: Whenever you add or delete rules you should overwrite the changes to the iptables.rules file using the following command

iptables-save > /etc/iptables.rules

How to assign a static IP address in Linux

Last Updated on Monday, 17 October 2011 03:21 Written by A.Jesin Monday, 17 October 2011 03:21

This article explains assigning a static IP to your Linux machine through the command line. If you’re assigning a public IP address, you should’ve purchased it from your ISP. Assigning the IP address in Linux requires you to edit the network configuration file. The network interface files are located at different places according the Linux OS variant. This article will cover both Red Hat and Debian variants. You need to logged in as the root user to edit these files, or you should have sudo permissions. Read More…

Linux ACL Tutorial

Last Updated on Sunday, 9 October 2011 02:46 Written by A.Jesin Sunday, 9 October 2011 02:46

Access Control Lists( (ACLs) are a way to assign fine tuned permissions in Linux apart from using the chmod command. When the chmod command is used only one owner and one group can be assigned permissions on a file or directory. If multiple users need access to a resource we need to place them in a group and then give that group the necessary permissions. But with File ACLs in Linux we can assign fine grained permissions to each user and group on a file and even deny access to a particular user even if the file has world permissions. This tutorial on Linux File ACL will explain the usage of the commands getfacl and setfacl. Read More…