10/4/08

Useful commands to know in Linux.

Switching from a windows environment to Linux is a big change, the most obvious to overcome was knowing what commands to use to get information about your operating system. This is why I am putting this list together, to minimize the amount of search needed to find the right information.

This list will be updated from time to time.

ifconfig - this command is used to configure and control network interfaces, simply running this command will display the current state of your network interface.

netstat - combining switch with this command will will display a lot of useful information about your network, such as Routing Tables, all open ports, all listening ports and more.

This command will display a numeric routing table, (-n) tells the command to output IP address instead of hostname, (-r) prints the routing table on your screen.

Example: netstat -nr

This command will display all open ports.

Example: netstat -a

This will display all listening ports.

Example: netstat -l

Installing MySQL on Debian

apt-get install mysql-server mysql-client libmysqlclient-dev

mysqladmin -u root password yourrootsqlpassword

When you run netstat -tap you should now see a line like this:

tcp 0 0 localhost.localdo:mysql *:* LISTEN 2449/mysqld

Installing Apache, PHP and a few other modules

apt-get install apache2 apache2-doc
apt-get install php4 php4-cli php4-common php4-curl php4-dev php4-domxml php4-gd php4-imap php4-ldap php4-mcal php4-mhash php4-mysql php4-odbc php4-pear php4-xslt curl imagemagick

FreeRADIUS

Fetch FreeRADIUS and some tools:

apt-get install freeradius freeradius-mysql freeradius-dialupadmin

Apache Cheat Sheet

Setup a Virtual Domain

NameVirtualHost *
<VirtualHost * >
DocumentRoot /web/example.com/www
ServerName example.com
ServerAlias example.com
CustomLog /web/example.com/logs/access.log combined
ErrorLog /web/example.com/logs/error.log
</VirtualHost>

Include another conf file

Include /etc/apache/virtual-hosts/*.conf

Hide apache version info

ServerSignature Off
ServerTokens Prod

Custom 404 Error message

ErrorDocument 404 /404.html

Create a virtual directory (mod_alias)

Alias /common /web/common

Perminant redirect (mod_alias)

Redirect permanent /old http://example.com/new

Create a cgi-bin

ScriptAlias /cgi-bin/ /web/cgi-bin/

Process .cgi scripts

AddHandler cgi-script .cgi

Add a directory index

DirectoryIndex index.cfm index.cfm

Turn off directory browsing

Options -Indexes

Turn on directory browsing

<Location /images>
Options +Indexes
</Location>

Create a new user for basic auth (command line)

htpasswd -c /etc/apacheusers

Apache basic authentication

AuthName "Authentication Required"
AuthType Basic
AuthUserFile /etc/apacheusers
Require valid-user

Only allow access from a specific IP

Order Deny,Allow
Deny from all
Allow from 127.0.0.1

Only allow access from your subnet

Order Deny,Allow
Deny from all
Allow from 176.16.0.0/16

mod_rewrite

Turn on the rewrite engine

RewriteEngine On

Redirect /news/123 to /news.cfm?id=123

RewriteRule ^/news/([0-9]+)$ /news.cfm?id=$1 [PT,L]

Redirect www.example.com to example.com

RewriteCond %{HTTP_HOST} ^www\.example\.com$ [NC]
RewriteRule ^(.*)$ http://example.com$1 [R=301,L]

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