tutorial 9ku

tutorial - Testing firewall rules

Sometimes it is handy to check firewall rules without coordinating a test with the end user. For these tests, use the hping2 utility to "spoof" traffic coming from the source IP address(es) used in the firewall rules.

At the same time, monitor the internal and external network interfaces on the firewall to make sure traffic is reaching the firewall and allowed through the firewall. In order to do this, you must have root access on the firewall and on the machine running hping2.

Example firewall rule:
Permit source IP 192.168.1.1 to communicate with destination IP 10.0.0.1 over TCP port 1000.

To test the rule, issue the following hping2 command:
hping2 -a 192.168.1.1 10.0.0.1 -p 1000

At the same time, log into the firewall and run the following commands (example with internal network interface etho and external network interface eth1)

In window 1:
tcpdump -i eth0 host 192.168.1.1 and port 1000

In window 2:
tcpdump -i eth1 host 10.0.0.1 and port 1000

If you do not see any output in window 1, traffic is not reaching the firewall. A choke router or other packet-filtering device may not be allowing the traffic to reach the firewall.

If you see output in window 1 but not in window 2, traffic is not being allowed through the firewall. Check the firewall rulebase for any errors.

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source:http://linuxpoison.blogspot.com/2008/03/13578175805532.html

tutorial - ctime, atime, and mtime

It is important to distinguish between a file or directory's change time (ctime), access time (atime), and modify time (mtime).

ctime -- In UNIX, it is not possible to tell the actual creation time of a file. The ctime--change time--is the time when changes were made to the file or directory's inode (owner, permissions, etc.). It is needed by the dump command to determine if the file needs to be backed up. You can view the ctime with the ls -lc command.

atime -- The atime--access time--is the time when the data of a file was last accessed. Displaying the contents of a file or executing a shell script will update a file's atime, for example. You can view the atime with the ls -lu command.

mtime -- The mtime--modify time--is the time when the actual contents of a file was last modified. This is the time displayed in a long directoring listing (ls -l).

In Linux, the stat command will show these three times.

source:http://linuxpoison.blogspot.com/2008/03/135781758010301.html

tutorial - HowTo run an Perl or shell script using procmail

This is a sample (example) of procmail configuaration and in this configuation we want to run some script

:0 * conditions, if any | your-script-here

Obviously, you are not restricted to Perl or shell scripts. Anything you can run from a Unix command prompt can be run from Procmail.

source:http://linuxpoison.blogspot.com/2008/03/13578175809093.html

tutorial - Are you an Ubuntu User? - Get Counted !!!

The Ubuntu Counter Project is like a miniature version of The Linux Counter. It aims to catalogue the number of registered machines using the numerous varients of the Ubuntu Linux distribution.

Why? Because, quite simply, Ubuntu rocks.

To register your Ubuntu machines, simply register yourself as a user, and add your machines to your account.

Once registered, you will have a user button (like the ones below) to place on your website, in forum signatures or wherever you want!

source:http://linuxpoison.blogspot.com/2008/03/1357817580302.html

tutorial - Edit grub.conf file with QGRUBEditor

Anyone who runs more than one operating system has had to deal with GNU GRUB (the GRand Unified Bootloader). Grub is the tool that allows you to pick which operating system to book when you turn your computer on. But you can do a ton more than that by configuring it and derailing from the standard configuration. Unfortunately, until recently users were forced to open up cryptic config files in text editors and try and figure out what to do based on the comments (or, more diligently, by reading man pages). Now, users can use QGRUBEditor.

source:http://linuxpoison.blogspot.com/2008/04/13578175804597.html

tutorial - How security Certificates works?

Certificate security provides a mechanism for achieving encrypted communications over unsecured networks and is built upon the Public Key Infrastructure (PKI). Certificates use asymmetrical cryptography whereby different keys are used for the encryption and decryption process.

Under public key encryption two keys are required, a public key and a private key. A client contacts a Certificate Authority (CA) to obtain both of these keys. The public key is then provided to anyone who needs to send encrypted data to the client. The sender uses the this public key to encrypt the data and send it to the original client. On receipt, the client decrypts the message using the private key (which is the only key which can be used to decrypt the message since this is asymmetrical encryption.

So far we have looked at certificates in terms of encrypting data between parties where the public key is used to encrypt a message to a client and the client's private key is used to decrypt the message. When using certificates as a means of authentication this process is reversed. In such a situation the client encrypts its signature using its private key and sends it to the receiving system. If the sending client is who it claims to be the receiving system should be able to decrypt the signature using the client's public key. If the decryption using the public key fails, the sender is not who they claim to be and the authentication has failed.

source:http://linuxpoison.blogspot.com/2008/04/135781758017130.html

tutorial - Automate Wallpapers directly from Flickr and Webshots to your Linux desktop

Webilder delivers stunning wallpapers to your Linux desktop, directly from Flickr and Webshots. You choose what keywords (tags) to watch for, and photos are automatically downloaded to your computer. Webilder can also change the wallpaper every few minutes.

It also include:

A simple photo collection browser, that will let you view the images in fullscreen, or set them as a wallpaper. Browser integration for webshots - downloaded images are automatically added to your collection. Command-line photo downloader.

Download Webilder: here

source:http://linuxpoison.blogspot.com/2008/04/135781758019310.html

tutorial - CrossFTP - synchronization tool and FTP/FXP/FTPS/SFTP/WebDav(s) client

CrossFTP is an excellent FTP client. CrossFTP Pro is a synchronization tool and FTP/FXP/FTPS/SFTP/WebDav(s) client.

CrossFTP is an excellent FTP client for reliable transfers. CrossFTP uses a familiar, Explorer-like interface that even the most novice user can master in minutes. It offers features such as Web starting, international encoding support, archive browsing, site password encryption, drag-and-drop, filtering, Web searching, image quick viewer, auto-reconnecting and anti-idle, and sound triggers, etc.

CrossFTP Pro is a turbo synchronization tool and FTP/FXP/FTPS/SFTP/WebDav(s) client. It provides value-added features like secure and multi-thread transports, remote file editing, speed limitation, synchronization, etc.

This application requires GTK+ version 1.2.x. and Sun Java 1.4+

Download CrossFTP : Here

source:http://linuxpoison.blogspot.com/2008/04/135781758012736.html

tutorial - Comparing Three Files by using diff3

The diff3 command compares three files and outputs descriptions of their differences. Its arguments are as follows:

diff3 options... mine older yours

The files to compare are mine, older, and yours. At most one of these three file names may be -, which tells diff3 to read the standard input for that file.

An exit status of 0 means diff3 was successful, 1 means some conflicts were found, and 2 means trouble.

read the man pages for detail options

source:http://linuxpoison.blogspot.com/2008/04/13578175809873.html

tutorial - How To Find Mac Address In Linux

You can think of a Mac address as a serial number for your network card. It is a unique six two-digits hexadecimal numbers separated by colons. It is used for routing traffic on a network.

In this example I will show you how to find your mac address in Ubuntu. This command should work any any terminal. Some distributions of linux you may need to be logged in as SU to see this information.

Open a terminal window and execute the command : ifconfig

source:http://linuxpoison.blogspot.com/2008/04/1357817580950.html

tutorial - Linux Runlevel Descriptions

Runlevel	Runlevel Description
Runlevel 0	The halt runlevel - this is the runlevel at which the system shuts down. For obvious reasons it is unlikely you would want this as your default runlevel.
Runlevel 1	Single runlevel. This causes the system to start up in a single user mode under which only the root user can log in. In this mode the system does not start any networking or X windowing, X or multi-user services. This run level is ideal for system admins to perform system maintenance or repair activities.
Runlevel 2	Boots the system into a multi-user mode with text based console login capability. This runlevel does not, however, start the network.
Runlevel 3	Similar to runlevel 2 except that networking services are started. This is the most common runlevel for server based systems that do not require any kind of graphical desktop environment.
Runlevel 4	Undefined runlevel. This runlevel can be configured to provide a custom boot state.
Runlevel 5	Boots the system into a networked, multi-user state with X Window System capability. By default the graphical desktop environment will start at the end of the boot process. This is the most common run level for desktops or workstation use.
Runlevel 6	Reboots the system. Another runlevel that you are unlikely to want as your default.

source:http://linuxpoison.blogspot.com/2008/04/13578175807301.html

tutorial - Working with Linux Services

There are number of ways to control what services get started using both command line and graphical tools without having to going into the depths of your Linux system.

The command line tool chkconfig (usually located in /sbin) can be used to list and configure which services get started at boot time. To list all service settings run the following command:

/sbin/chkconfig --list

This will display a long list of services showing whether or not they are started up at various runlevels. You may want to narrow the search down using Linux grep command. For example to list the entry for the HTTP daemon you would do the following:

/sbin/chkconfig --list | grep httpd

which should result in something like:

httpd 0:off 1:off 2:off 3:on 4:off 5:off 6:off

Alternatively you may just be interested to know what gets started for runlevel 3:

/sbin/chkconfig --list | grep '3:on'

chkconfig can also be used to change the settings. If we wanted the HTTP service to start up when we at runlevel 5 we would issue the following command:

/sbin/chkconfig --level 5 httpd on

A number of graphical tools are also available for administering services. On RedHat you can run the following command:

redhat-config-services

The equivalent command on Fedora Core is:

system-config-services

The above graphical tools allow you to view which services will start for each runlevel, add or remove services for each runlevel and also manually start or stop services.

source:http://linuxpoison.blogspot.com/2008/04/13578175802475.html

tutorial - Using GPG

1. Key Generation

gpg # Initialize GPG for this user (e.g. create ~/.gnupg). Only have to run once.
gpg --gen-key # Start key generation process. Follow prompts.

2. Viewing Keys

gpg --list-keys # View public keys
gpg --list-secret-keys # View private keys

3. Exporting Public Keys

gpg --export # Exports key in binary format
gpg --export --armor # Export in a usable, ASCII format

4. Importing Public Keys

gpg --import /path/to/public/key/file

5. Encrypting a Message

gpg --encrypt --armor --recipient message_file

6. Decrypting a Message

gpg encrypted_message_file

You will be prompted for the filename to use for the output of the decryption process.

7. Encrypting with a Symmetric Key

gpg --symmetric --armor message_file

8. Signing and Encrypting a Message

gpg --sign --encrypt --armor --recipient message_file

9. Creating a Detached Signature

gpg --detach-sign --armor message_file # Sender
gpg --verify message_file.asc message_file # Recipient

10. Signing Another's Public Key

Alice is going to sign Bob's key.

# First, user A must do:
gpg --sign-key user_B
gpg --export --armor user_B > B.key

# Then, user_b must do:
gpg --import B.key

source:http://linuxpoison.blogspot.com/2008/04/13578175801985.html

tutorial - Execute more than one commands

Executing the second command only if the first is successful

To do this you would type: command1 && command2

command2 will be executed if command1 successfully completes (if command1 fails command2 won't be run). This is called a logical AND.

Executing the second command only if the first fails

To do this you would type: command1 || command2

command2 will be executed if command1 does not successfully completes (if command1 is successful command2 won't be run). This is called a logical OR.

Executing commands sequentially

To execute command sequentially regardless of the success/failure of the previous you simply type: command1; command2

command2 will execute once command1 has completed.

source:http://linuxpoison.blogspot.com/2008/04/13578175809888.html

tutorial - How To increase the MAX file upload size in PHP

There is a variable in your php.ini file (Location of this file may differ for different distribution but is mainly located in /etc directory or in /etc/php directory, try to find this file)

Open this php.ini file in any text editor and locate the section "File Uploads", now in this section, first, you need to enable the upload of file by modifying the variable "file_uploads = On" and next you can increase the upload limit to any value that you may required by modifying the value of "upload_max_filesize = 20M".

As you can see here in my case I have made the limit to 20MB, you can put your any required value here and restart the apache server to take the effect.

source:http://linuxpoison.blogspot.com/2008/04/13578175808690.html

tutorial - HTML to PS/PDF converter

htmldoc is a powerful simple-to-use tool which converts HTML to Postscript, PDF, or indexed HTML output. It provides a graphical user interface for manual document conversion -- useful for tasks such producing printed manuals from web pages -- but it can also be used as a filter.

Installing from the command line (Fedora): yum install htmldoc
Installing using the graphical installer: Applications > Office/Productivity > htmldoc
Menu location after installation: Office > HTMLDOC
Command: /usr/bin/htmldoc
website: http://www.htmldoc.org/

source:http://linuxpoison.blogspot.com/2008/04/135781758012644.html

tutorial - Database explorer and query tool

CrunchyFrog is a database explorer and query tool for GNOME.

Currently PostgreSQL, MySQL, Oracle, SQLite3 databases and LDAP servers are supported for browsing and querying. More databases can be added using the plugin system.

This application requires GTK+ version 2.12.x. Other dependencies include:
For a (almost) complete list of dependencies see http://code.google.com/p/crunchyfrog/wiki/Requirements

Download : here

source:http://linuxpoison.blogspot.com/2008/04/13578175802069.html

tutorial - How To Disable a User Account in Linux

Linux systems use /etc/shadow to store the encrypted user passwords. The quickest way to disable a user is to alter is password stored in /etc/shadow. Normally an active user account will have one line in /etc/shadow that will look like:

user:$1$eFd7EIOg$EeCk6XgKktWSUgi2pGUpk.:13852:0:99999:7:::

where the second field is the encrypted password.

If we replace the password with “*” or “!” this will make the account unusable, and it will mean that no login is permitted for the user: user:*:13852:0:99999:7:::

This method has the disadvantage that the user password will be lost (unless saved somewhere, etc.) in the case we will want to re-enable it again later. From this point of view a much better method is to use the passwd command to lock the account: passwd -l

and the output of the successful change will be “Password changed.”. This actually just changes the shadow file and adds “!” in front of the user password:

user:!$1$eFd7EIOg$EeCk6XgKktWSUgi2pGUpk.:13852:0:99999:7:::

Of course we could do this manually ourselves also if we want ;-).

If you will ever need to re-enable the account just unlock it: passwd -u
or just remove manually the “!” character from the user’s password line in /etc/shadow.

source:http://linuxpoison.blogspot.com/2008/04/135781758011558.html

tutorial - How to find - Size of a directory & Free disk space

‘du’ - Finding the size of a directory

$ du
Typing the above at the prompt gives you a list of directories that exist in the current directory along with their sizes. The last line of the output gives you the total size of the current directory including its subdirectories. The size given includes the sizes of the files and the directories that exist in the current directory as well as all of its subdirectories. Note that by default the sizes given are in kilobytes.

$ du /home/nikesh
The above command would give you the directory size of the directory /home/nikesh

$ du -h
This command gives you a better output than the default one. The option ‘-h’ stands for human readable format. So the sizes of the files / directories are this time suffixed with a ‘k’ if its kilobytes and ‘M’ if its Megabytes and ‘G’ if its Gigabytes.

$ du -ah
This command would display in its output, not only the directories but also all the files that are present in the current directory. Note that ‘du’ always counts all files and directories while giving the final size in the last line. But the ‘-a’ displays the filenames along with the directory names in the output. ‘-h’ is once again human readable format.

$ du -c
This gives you a grand total as the last line of the output. So if your directory occupies 30MB the last 2 lines of the output would be

30M .
30M total

The first line would be the default last line of the ‘du’ output indicating the total size of the directory and another line displaying the same size, followed by the string ‘total‘. This is helpful in case you this command along with the grep command to only display the final total size of a directory as shown below.

$ du -ch | grep total
This would have only one line in its output that displays the total size of the current directory including all the subdirectories.

$ du -s
This displays a summary of the directory size. It is the simplest way to know the total size of the current directory.

$ du -S
This would display the size of the current directory excluding the size of the subdirectories that exist within that directory. So it basically shows you the total size of all the files that exist in the current directory.

$ du –exculde=mp3
The above command would display the size of the current directory along with all its subdirectories, but it would exclude all the files having the given pattern present in their filenames. Thus in the above case if there happens to be any mp3 files within the current directory or any of its subdirectories, their size would not be included while calculating the total directory size.

-
‘df’ - finding the disk free space / disk usage

$ df
Typing the above, outputs a table consisting of 6 columns. All the columns are very easy to understand. Remember that the ‘Size’, ‘Used’ and ‘Avail’ columns use kilobytes as the unit. The ‘Use%’ column shows the usage as a percentage which is also very useful.

$ df -h
Displays the same output as the previous command but the ‘-h’ indicates human readable format. Hence instead of kilobytes as the unit the output would have ‘M’ for Megabytes and ‘G’ for Gigabytes.

source:http://linuxpoison.blogspot.com/2008/04/13578175809103.html

tutorial - HowTo Allow windows updates through squid

Add the following to your squid.conf, It 'MUST' be added near the top before any ACL that require authentication.

acl windowsupdate dstdomain windowsupdate.microsoft.com
acl windowsupdate dstdomain .update.microsoft.com
acl windowsupdate dstdomain download.windowsupdate.com
acl windowsupdate dstdomain redir.metaservices.microsoft.com
acl windowsupdate dstdomain images.metaservices.microsoft.com
acl windowsupdate dstdomain c.microsoft.com
acl windowsupdate dstdomain www.download.windowsupdate.com
acl windowsupdate dstdomain wustat.windows.com
acl windowsupdate dstdomain crl.microsoft.com

acl CONNECT method CONNECT
acl wuCONNECT dstdomain www.update.microsoft.com

http_access allow CONNECT wuCONNECT localnet
http_access allow windowsupdate localnet

The above config is also useful for other automatic update sites such as Anti-Virus vendors, just add their domains to the acl.

source:http://linuxpoison.blogspot.com/2008/04/135781758016367.html

tutorial - Get Hostname from IP address

To get the hostname from the IP address.
The simplest way is to use the “host” utility provided by Gnu/Linux. Just run…

poison:~ # host 64.233.187.99
99.187.233.64.in-addr.arpa domain name pointer jc-in-f99.google.com.
poison:~ #

This will query the name server and provide you with the hostname of the IP address.By default it will query the nameserver listed in the /etc/resolv.conf file.

source:http://linuxpoison.blogspot.com/2008/04/135781758019216.html

tutorial - Working with Archives

Working with tar Archives

To create an archive of a directory tree with tar, you can do something like this:

nikesh@poison:~/temp> tar -cf directory.tar directory/
nikesh@poison:~/temp> ls
directory directory.tar

The preceding command creates (c), verbosely (v), the file (f) directory.tar, which is a tar archive, by running tar on directory.

If you want to list the files in the archive:

nikesh@poison:~/temp> tar -tf directory.tar
directory/
directory/afile
directory/bfile

Here the option lists the contents of the file (f) directory.tar.

Using gzip Compression with tar

If you want to create a gzipped tar archive (the -z option implies compression, while the c means create):

nikesh@poison:~/temp> tar -zcf directory.tgz directory/
nikesh@poison:~/temp> ls
directory directory.tgz

The original is still there, unlike when we compressed a single file with gzip. (Note that .tgz and .tar.gz are used interchangeably for filenames of gzipped tar archives.)

To list the files in this case, use the following:

nikesh@poison:~/temp> tar -tzf directory.tgz
directory/
directory/afile
directory/bfile

Using bzip2 Compression with tar

If you want to use compression with bzip2 instead of gzip, the required option is -j rather than -z:

nikesh@poison:~/temp> tar -jcf directory.tar.bz2 directory/
nikesh@poison:~/temp> ls
directory directory.tar.bz2

nikesh@poison:~/temp> tar -jtf directory.tar.bz2
directory/
directory/afile
directory/bfile

Unpacking tar Archives

To unpack a tar archive, you need to use the -x option (for extract):

nikesh@poison:~/temp> tar -xvf directory.tar
or
nikesh@poison:~/temp> tar -zxvf directory.tgz
or
nikesh@poison:~/temp> tar -jxvf directory.tar.bz2

Here the options have the following meanings:
The -x option to tar means extract.
The z option implies that you are uncompressing a tar archive where gzip compression has been used.
The joption is needed if you are extracting an archive where bzip2 compression has been used.

Working with zip Archives

The common zip archive format (associated with the DOS and Windows programs PKZIP and WinZip among others) is supported on Linux. To unzip a zip archive, simply do the following:

nikesh@poison:~/temp> unzip zipfile.zip

To create a zip archive of the current directory:

nikesh@poison:~/temp> zip -r ~/newzip.zip .

This will recursively zip up the current directory and create the zip file newzip.zip in you’re your home directory (~).
The program zipinfo will give a listing and information about compression ratios:

nikesh@poison:~/temp> zipinfo zipfile.zip

source:http://linuxpoison.blogspot.com/2008/04/13578175805616.html

tutorial - Great Comment on Linux Vs Windows

Some days back I was reading an article on OpenSuse 10.2 review (Linux Vs Windows) and fortunately I came across a great comments on that article …..

read below …..

Shaking my head at you guys (gals?)! 8^)

I’ve been using linux on my main computer for 5+ years, and on my webservers for over 10. Actually started with SUSE desktop (well tried Caldera 2.1 waaay back when UGH!), then went to Fedora to get the “latest & greatest.” (They usually had bleeding edge software before other distros… Mozilla, etc.). I’ve had to purchase Windows due to my job. Picked up Vista, couldn’t upgrade from ME, so got the XP upgrade instead.

Tried Ubuntu on a friends puter, liked it so tried it on mine. All good except could not make on the motherboard nVidia Ge6100 work. Had read some reviews about SUSE, so d/led it. Setting up dual boot. Windows & Linux can read FAT32, so decided to set up my box like this. The 1st 200Gb drive as NTFS XP, 200Gb #2 as linux, 400Gb as FAT32 shared between the 2 for docs, pics, music and such.

Has anyone installed Windoze lately or just purchased pre-installed?
It took about 1 1/2 hours just to format 200Gb!!! So don’t get picky about 30 or 40 minutes to install a linux distro!
And it only formatted 128Gb, so had to use System Commander to stretch it out to the full 200Gb!

Rebooted into my newly installed XP.
NO SOUND
NO INTERNET
NO PRINTER
Call ISP. duh! I needed to install the drivers off the CD that came with my motherboard. I’ve been installing Linux for so long, I forgot about that crap.
Everything just works from linux install. (Except nVidia problem mentioned earlier).
Rounded up my driver CDs and got all that working.
Can anyone explain to me why after paying $100USD for Windoze upgrade it could not do something my FREE linux programs do like install drivers for motherboards and printers???

So now I have a great OS system installed on my box… NOT!
NO SOFTWARE!!!
Installed Office 2003, an old copy of CorelDraw I had, and some other webmaster programs, like ftp, ssh, 1stPage, etc. (You know, programs you get installed for free when using linux…)
Shelled out $40USD for Windows Live virus etc protector.
If I wasn’t dual booting, I’d still be looking around for buggy shareware to do simple things us Linux geeks just take for granted… (burn CDs, play games, make to do lists, bitTorrent, IM, etc.)

In all, it took me about 8 hours to get xp up and running close to the way I wanted.

Installed SUSE, complete with HUGE software stash, did complete update, changed a few things around like I wanted, and it only took me about 1 1/2 hours. That included formatting 3 times as much hard drive.

Oh yeah, I won’t go into trying to get FAT32 working on the large hard drive too much. Checked MS knowledge base. An older one said to go into device manager to format large hard drives. A newer article says, xp can’t do it, use your 95, 98 or ME install disk. HUH? Xp won’t see FAT32 formatted by System Commander, Linux, or DOS command line format. My conspiracy theory is that they knew Linux can read & write to it so they took it out of their OS. Shaking my head at Billie…

source:http://linuxpoison.blogspot.com/2008/04/135781758016770.html

tutorial - HowTo Forward the mail to many addresses using procmail

We just need to add more addresses to the action line:

:0
* ^Subject: This is urgent$ ! first@one.com second@two.net third@three.org

If you have a large list of recipients, you might prefer to store the addresses in an external file you can edit without mucking with your Procmail filters:

:0
* ^Subject: This is urgent$
! `cat addresses.txt`

source:http://linuxpoison.blogspot.com/2008/04/13578175804164.html

tutorial - Starting Qmail through Xinetd

Here is the entry info for starting Qmail through Xinetd

service smtp
{
flags = REUSE NAMEINARGS
socket_type = stream
protocol = tcp
wait = no
user = qmaild
server = /usr/sbin/tcpd
server_args = /var/qmail/bin/tcp-env -R /var/qmail/bin/qmail-smtpd
}

source:http://linuxpoison.blogspot.com/2008/12/135781758018656.html

tutorial - Configure Apache with with mod_deflate

mod_deflate is included in the Apache 2.0.x source package, and compiling it in is a simple matter of adding it to the configure command.

./configure --enable-modules=all --enable-mods-shared=all --enable-deflate

When the server is made and installed, the GZIP-encoding of documents can be enabled in one of two ways: explicit exclusion of files by extension; or by explicit inclusion of files by MIME type. These methods are specified in the httpd.conf file.

Explicit Exclusion

SetOutputFilter DEFLATE
DeflateFilterNote ratio
SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.(?:exe|t?gz|zip|bz2|sit|rar)$ no-gzip dont-vary
SetEnvIfNoCase Request_URI \.pdf$ no-gzip dont-vary

Explicit Inclusion

DeflateFilterNote ratio
AddOutputFilterByType DEFLATE text/*
AddOutputFilterByType DEFLATE application/ms*
application/vnd* application/postscript

Both methods enable the automatic GZIP-encoding of all MIME-types, except image and PDF files. Image files and PDF files are excluded as they are already in a highly compressed format. In fact, PDFs become unreadable by Adobe's Acrobat Reader if they are further compressed by mod_deflate or mod_gzip.

source:http://linuxpoison.blogspot.com/2008/04/135781758015586.html

tutorial - How To convert flv to avi Using FFmpeg

Move to the path where you have your video files:
cd /path/where/is/the/video

Run ffmpeg command with -i for input and output.avi is the output file in avi or mpg:
# ffmpeg -i input.flv output.avi

What is FFmpeg?
"FFmpeg is a collection of software libraries that can record, convert and stream digital audio and video in numerous formats. It includes libavcodec, an audio/video codec library used by several other projects, and libavformat, an audio/video container mux and demux library."

source:http://linuxpoison.blogspot.com/2008/04/135781758019498.html

tutorial - HowTo to get the lists of installed package/software on Fedora/RedHat/CentoOS/OpenSuse

You can list the packages that are installed on a RedHat or CentOS or Fedora or OpenSuse system, running this commands:

# rpm -qa

You can also redirect the list of packages to a file by using this command

# rpm -qa > /root/list.txt

You should remove packages you dont use for security reasons.

source:http://linuxpoison.blogspot.com/2008/04/13578175806977.html

tutorial - How TO install/Configure APF (Advanced Policy Firewall) Firewall

Advanced Policy Firewall (APF) is an iptables(netfilter) based firewall system designed around the essential needs of today's Internet deployed servers and the unique needs of custom deployed Linux installations. The configuration of APF is designed to be very informative and present the user with an easy to follow process, from top to bottom of the configuration file. The management of APF on a day-to-day basis is conducted from the command line with the 'apf' command, which includes detailed usage information and all the features one would expect from a current and forward thinking firewall solution.

Login to your server as root, then:
# Download -- http://www.r-fx.ca/downloads/apf-current.tar.gz
# tar -xvzf apf-current.tar.gz
# rm -f apf-current.tar.gz
# cd apf-*
# ./install.sh

Edit conf.apf
# cd /etc/apf
# vi conf.apf

Common ingress (inbound) TCP IG_TCP_CPORTS="20,21,22,25,53,80,110,143,443,465,993,995,2082,2083,2086,2087,2095,2096,3306,10000,35000_35999"

Common ingress (inbound) UDP
IG_UDP_CPORTS="20,21,53,1040"

Exit and save and then restart apf:
# service apf start

If APF is functioning fine, edit the conf.apf
# vi conf.apf

Set the DEVM parameter to 0DEVM="0"

Now you can Restart APF, and is done:
# service apf restart

Configure APF to start at boot
# chkconfig --add apf
# chkconfig --level 345 apf on

Summary of features:
- detailed and well commented configuration file
- granular inbound and outbound network filtering
- user id based outbound network filtering
- application based network filtering
- trust based rule files with an optional advanced syntax
- global trust system where rules can be downloaded from a central management server
- reactive address blocking (RAB), next generation in-line intrusion prevention
- debug mode provided for testing new features and configuration setups
- fast load feature that allows for 1000+ rules to load in under 1 second
- inbound and outbound network interfaces can be independently configured
- global tcp/udp port & icmp type filtering with multiple methods of executing filters (drop, reject, prohibit)
- configurable policies for each ip on the system with convenience variables to import settings
- packet flow rate limiting that prevents abuse on the most widely abused protocol, icmp
- prerouting and postrouting rules for optimal network performance
- dshield.org block list support to ban networks exhibiting suspicious activity
- spamhaus Don't Route Or Peer List support to ban known "hijacked zombie" IP blocks
- any number of additional interfaces may be configured as firewalled (untrusted) or trusted (not firewalled)
- additional firewalled interfaces can have there own unique firewall policies applied
- intelligent route verification to prevent embarrassing configuration errors
- advanced packet sanity checks to make sure traffic coming and going meets the strictest of standards
- filter attacks such as fragmented UDP, port zero floods, stuffed routing, arp poisoning and more
- configurable type of service options to dictate the priority of different types of network traffic
- intelligent default settings to meet every day server setups
- dynamic configuration of your servers local DNS revolvers into the firewall
- optional filtering of common p2p applications
- optional filtering of private & reserved IP address space
- optional implicit blocks of the ident service
- configurable connection tracking settings to scale the firewall to the size of your network
- configurable kernel hooks (ties) to harden the system further to syn-flood attacks & routing abuses
- advanced network control such as explicit congestion notification and overflow control
- special chains that are aware of the state of FTP DATA and SSH connections to prevent client side issues
- control over the rate of logged events, want only 30 filter events a minute? 300 a minute? - you are the boss
- logging subsystem that allows for logging data to user space programs or standard syslog files
- logging that details every rule added and a comprehensive set of error checks to prevent config errors
- if you are familiar with netfilter you can create your own rules in any of the policy files
- pluggable and ready advanced use of QoS algorithms provided by the Linux
- 3rd party add-on projects that compliment APF features

source:http://linuxpoison.blogspot.com/2008/04/13578175801292.html

tutorial - How To disable telnet service

Login as root to your server:

Edit /etc/xinetd.d/telnet
# vi /etc/xinetd.d/telnet

Search for: "disable = no"
Change it to: disable = yes

Save and Exit

Restart xinted
# /etc/rc.d/init.d/xinetd restart

source:http://linuxpoison.blogspot.com/2008/04/13578175809312.html