tag:blogger.com,1999:blog-32442569802628923612024-03-13T14:00:57.310-07:00LINUXAnonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-3244256980262892361.post-59985356006313847262014-08-28T06:06:00.002-07:002014-08-28T06:06:56.104-07:00LAMP WAMP & XAMMP<div dir="ltr" style="text-align: left;" trbidi="on">
<h3 style="background-color: white; color: #222222; font-family: arial, sans-serif; text-align: left;">
<span style="font-size: small;">Hello Friends. </span></h3>
<h3 style="background-color: white; color: #222222; font-family: arial, sans-serif; text-align: left;">
<span style="font-size: small;">Today i will discuss about the difference between wamp, lamp and xampp. All these three are used for php websites and acts as the local server so that you can see your working website without uploading it first.<br />By this all technology you don`t require any other<br />techonolgy.These all are called package. All have different working area with different different role.<br />First of all i will discuss about LAMP.</span></h3>
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<b>LAMP</b> :-LAMP is an acronym for a solution stack of free, open source software, referring to the first letters of Linux (operating system), Apache HTTP Server, MySQL (database software) and PHP (or sometimes Perl or Python), principal components to build a viable general purpose web server.</div>
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<strong>WAMP</strong> :-WAMPs are packages of independently-created programs installed on computers that use a Microsoft Windows operating system.</div>
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WAMP is an acronym formed from the initials of the operating system Microsoft Windows and the principal components of the package: Apache, MySQL and one of PHP, Perl or Python. Apache is a web server. MySQL is an open-source database. PHP is a scripting language that can manipulate information held in a database and generate web pages dynamically each time content is requested by a browser. Other programs may also be included in a package, such as phpMyAdmin which provides a graphical user interface for the MySQL database manager, or the alternative scripting languages Python or Perl. Equivalent packages are MAMP (for the Apple Mac) and LAMP (for the Linux operating system).</div>
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<strong>XAMMP</strong> :-XAMPP is a free and open source cross-platform web server solution stack package, consisting mainly of the Apache HTTP Server, MySQL database, and interpreters for scripts written in the PHP and Perl programming languages.</div>
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Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-52513682537735519092014-07-01T00:20:00.002-07:002014-07-01T00:20:18.563-07:00The Secure Shell (ssh)<div dir="ltr" style="text-align: left;" trbidi="on">
<a href="https://www.blogger.com/null" name="WhatIsSsh">
</a><br />
<h1>
<a href="https://www.blogger.com/null" name="WhatIsSsh"><b><span style="font-weight: normal;">What is ssh?</span></b></a></h1>
Ssh is set of programs which employ public/private key technology for
authenticating and encrypting sessions between user accounts on
distributed hosts on the Internet. It can be compiled and used by a
normal user without having to ask permission or assistance from the
system administrator, or the system administrator can install it as a
plug-in replacement for the Berkeley "r" utilities without the users
needing to know it is there at all (or do anything to learn how to use
it). <br />
Ssh can also be used as a way to "tunnel" other protocols, such as the
X Window System protocol, adding encryption to the channel to improve
security against packet sniffing and "man in the middle" attacks.
When used with X, ssh looks like a normal (albeit a proxy) X server on
the local machine which redirects X protocol communication across an
encrypted channel to the actual X server on the other end. <br />
<a href="https://www.blogger.com/null" name="HowDoesItWork">
</a><br />
<h1>
<a href="https://www.blogger.com/null" name="HowDoesItWork">How does ssh work?</a></h1>
Ssh works by the exchange and verification of information, using
public and private keys, to identify hosts and users. It then
provides encryption of subsequent communication, also by the use of
public/private key cryptography.
In describing ssh here, the term <em>client</em> means a workstation
or PC that you are already logged in to, e.g., your own personal
workstation or a group workstation that provides XDM session
management for several X terminals. The term <em>server</em> means a
secondary remote workstation that you wish to log in to to do some
work; a login session server. <br />
Put simply, the client is where you type "<tt>rlogin server</tt>" or
"<tt>rcp file server:newfile</tt>" and the server is where you get a
new login session and shell prompt or are copying files,
respectively. <br />
As a user, you generate an "identity" on the client system by running
the <tt>ssh-keygen</tt> program. This program creates a subdirectory
<tt>$HOME/.ssh</tt> and inserts in it two files named
<tt>identity</tt> and <tt>identity.pub</tt> which contain your private
and public keys for your account on the client system. This latter
file can then be appended to a file
<tt>$HOME/.ssh/authorized_keys</tt> that should reside on any/all
servers where you will make ssh connections. <br />
As a system administrator, you generate a public and private key pair
for the system itself. By use of this information contained within
the system itself, the possibility of someone spoofing the system's
identity by faking IP addresses or munging up DNS records that
associate IP addresses and domain names is removed. You would have to
break into the system and steal its private key in order to
sucessfully pretend to be that system. This is a big improvement in
security. <br />
The biggest task if you manage a large number of systems that are
meant to be used together is collecting and distributing the keys that
identify all the hosts which run ssh. Tools exist for handling this
task: ssh includes the program <tt>make-ssh-known-hosts.pl</tt> (which
requires <tt>POSIX.pm</tt> be installed in your Perl library
directory) and another script (<a href="http://www.uni-karlsruhe.de/%7Eig25/ssh-faq/comp-host-list">http://www.uni-karlsruhe.de/~ig25/ssh-faq/comp-host-list</a>)
is available on the Internet. <br />
See also: Kimmo Suominen's <a href="http://www.tac.nyc.ny.us/%7Ekim/ssh/">Getting started with SSH</a>.<br />
<a href="https://www.blogger.com/null" name="HowDoIUseIt">
</a><br />
<h1>
<a href="https://www.blogger.com/null" name="HowDoIUseIt">How do I use ssh?</a></h1>
First, you need to <a href="http://staff.washington.edu/dittrich/misc/ssh/#WhereCanYouGetIt">get and install ssh</a>
on your client workstation, plus it must be installed on the remote
system you wish to connect to. You can do this for your own account,
or your system administrator can install it for the entire system.
Once installed, there are several ways you can use ssh, each with
varying steps you must go through first. <br />
The most basic use of ssh is transparent when compared with the
standard Berkeley "r" utilities. In fact, a system administrator can
install ssh on both client and remote server workstations and users
who connect using <tt>rlogin server</tt> will see no difference
whatsoever, nor will they need to know anything new. This kind of use
gets you the most basic protection of encrypted sessions from systems
with ssh installed, usually with a fall back capability to the old
(and less secure) Berkeley methods if the other system does not
support ssh. <br />
If you wish to make security tighter, you can stop using
<tt>.rhosts</tt> and <tt>/etc/hosts.equiv</tt> files (or disable the
Berkeley utilities altogether) and only allow passwordless connections
with ssh keys. <br />
Each system has its own public/private key pair that identifies it to
other systems. A client system's public key can be placed in a server
system's <tt>/etc/ssh_known_hosts</tt> file to allow the server to
authenticate the client by a key exchange dialog. <br />
If the client host's public key (from the
<tt>/etc/ssh_host_key.pub</tt> file) is found in the in the server's
<tt>/etc/ssh_known_hosts</tt> file, and you place the host name in
your own <tt>.rhosts</tt> or <tt>.shosts</tt> file, you get the same
passwordless connection behavior as the standard Berkeley "r"
utilities. If the client's key is not found, ssh will prompt you for
the password on the server and will transmit this password -- in
encrypted form, rather than plain text -- to the server for
authenticating your login. This method involves the system
administrator, who must place the client's public keys in the server's
<tt>/etc/ssh_known_hosts</tt> file. There is another way to use ssh
that doesn't require the administrator's intervention. <br />
Each user account also has a public and private key that identifies
that user account. You get this key when you run the
<tt>ssh-keygen</tt> program. It creates a directory called
<tt>$HOME/.ssh</tt> and puts the keys in there. You can now take your
public key, found in the <tt>$HOME/.ssh/identity.pub</tt> file and
place it on the server in your <tt>$HOME/.ssh/authorized_keys</tt>
file. Once you have done this, even though the server doesn't know
the key of the client workstation, it <em>does</em> now know your key
and will allow the login to your account without a password. <br />
To use the X Window System protocol tunneling (if enabled), you only
need to log in successfully and ssh will create a DISPLAY environment
variable for you that points to a proxy X server on the server system,
which passes X protocol traffic to the real X server on the client
system. You can start running X client programs as soon as you get a
shell prompt. </div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-73791839308601896252014-03-12T23:54:00.000-07:002014-03-12T23:54:37.158-07:00 Configuring Bind Non Recursive<div dir="ltr" style="text-align: left;" trbidi="on">
<div style="text-align: center;">
<span style="font-size: large;">Configuring Bind Non Recursive<br /> </span></div>
<div>
<div id="page-content">
When configuring the bind DNS name server, it's almost always beneficial to restrict who can perform recursive queries.<br />
A recursive query occurs when your DNS server is queried for a domain
that it currently knows nothing about, in which case it will try to
resolve the given host by performing further queries (e.g. by starting
at the root servers and working out, or by simply passing the request to
yet another DNS server).<br />
When this happens for arbitrary queries on the Internet, your DNS
server is open to anybody, so they can cost you bandwidth for their DNS
queries.<br />
However, there are situations that call for recursive queries being
answered. For example, if you have one DNS server serving your local
network, you may want all of your local computers to use your DNS
server.<br />
The solution is to add a line to the 'options' of your bind configuration. For example: -<br />
<br />
<br />
<div class="code">
<pre><code>options {
allow-recursion { 127.0.0.1; 192.168.1.0/24; 192.168.2.1; };
};</code>
</pre>
</div>
<br />
<br />
<br />
This would allow hosts localhost, 192.168.2.1, and the network
192.168.1.0/24 to use this DNS server for recursive lookups (e.g. as a
general name server). For everyone else, the server will only answer
queries for what's in the local zone files and in the cache.<br />
On Debian, this is placed in '/etc/bind/named.conf.options', other servers may be configured in '/etc/bind/named.conf'<br />
</div>
</div>
</div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-84999846301458935322014-03-06T21:21:00.000-08:002014-03-06T21:21:23.231-08:00Domain Name System<div dir="ltr" style="text-align: left;" trbidi="on">
<br />
<br />
<b><span style="font-size: large;">DNS stands for Domain Name System, or Domain Name Server.</span></b><br />
<br />
<br />
<b><span style="font-size: large;">
</span></b><b><span style="font-size: large;">DNS resolves an <span style="color: black;"><a href="http://www.thegeekstuff.com/2012/01/ip-address-fundamentals/">IP address</a></span> to a hostname or vice versa.</span></b><br />
<b><span style="font-size: large;">
</span></b><b><span style="font-size: large;">DNS is basically a large database which resides on various computers
that contains the names and IP addresses of various hosts/domains. Other
than ip-address DNS also associates various information with the domain
names.</span></b>
<b><span style="font-size: large;"><span id="more-14925"></span></span></b><br />
<b><span style="font-size: large;">
</span></b><h3>
<span style="color: blue;"><span style="font-size: large;">Structure of a DNS</span></span></h3>
<b><span style="font-size: large;">
</span></b><b><span style="font-size: large;">DNS uses a hierarchical tree based name structure. At top of the tree
is the “root” ( represented as a dot (.) ) followed by the TLD ( Top
Level Domain ), then by the domain-name and any number of lower level
sob-domains separated by a dot.</span></b><br />
<b><span style="font-size: large;">
</span></b><b><span style="font-size: large;">The Top Level Domains are divided into 2 categories:</span></b><br />
<b><span style="font-size: large;">
</span></b><ul>
<li><b><span style="font-size: large;">1. Generic TLD (gTLD)</span></b></li>
<li><b><span style="font-size: large;">2. Country Code TLD (ccTLD)</span></b></li>
</ul>
<b><span style="font-size: large;">
</span></b><b><span style="font-size: large;">Below are some of the common Generic Top Level Domains:</span></b><br />
<b><span style="font-size: large;">
</span></b><ul>
<li><b><span style="font-size: large;">.com – comercial web sites</span></b></li>
<li><b><span style="font-size: large;">.org – non profit organizations web sites</span></b></li>
<li><b><span style="font-size: large;">.edu – restricted to schools and institutions.</span></b></li>
<li><b><span style="font-size: large;">.net – originally for network infrastructures, now unrestricted</span></b></li>
</ul>
</div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0Ernakulam, Kerala, India10.05276592628751 75.9452820103615529.92763192628751 75.783920510361554 10.177899926287509 76.10664351036155tag:blogger.com,1999:blog-3244256980262892361.post-43714025389994882772014-03-06T21:09:00.002-08:002014-03-06T21:09:49.926-08:00What is the difference between a Registry and a Registrar?<div dir="ltr" style="text-align: left;" trbidi="on">
<br />
<br />
<br />
<b><span style="font-size: large;">A registry provides direct services to registrars only, not Internet
end-users. The Registry database contains only Domain Name service (DNS)
information (Domain Name, name server names and name server Internet
Protocol [IP] numbers) along with the name of the Registrar that
registered the name and basic transaction data. It does not contain any
Domain Name Registrant or contact information.
A Registrar provides direct services to Domain Name registrants. The
Registrar database contains customer information in addition to the DNS
information contained in the registry database. Registrars process name
registrations for Internet end-users and then send the necessary DNS
information to a Registry for entry into the centralized Registry
database and ultimate propagation over the Internet. </span></b></div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-71190622087785205032014-03-04T01:07:00.000-08:002014-03-04T01:07:21.189-08:00The /etc/fstab File<div dir="ltr" style="text-align: left;" trbidi="on">
<h4>
<span style="color: blue;"><br /></span></h4>
<div style="text-align: center;">
<h2>
<span style="color: #cc0000;"><i><span style="font-weight: normal;"><span style="color: blue;">/etc/fstab</span></span></i></span></h2>
</div>
<h4>
<span style="color: #cc0000;"></span></h4>
<h4>
<span style="color: #cc0000;">
</span></h4>
<table style="width: 100%px;"><tbody>
<tr><td width="10%"><h4>
<span style="color: #cc0000;"><br /></span></h4>
</td><td width="80%"><h4>
<span style="color: #cc0000;"><br /></span>
</h4>
<h4>
<span style="color: #cc0000;"><i>fstab</i> is a system configuration file on <a href="http://www.linfo.org/linuxdef.html">Linux</a> and other <a href="http://www.linfo.org/unix-like.html">Unix-like</a> <a href="http://www.linfo.org/operating_systems_list.html">operating systems</a> that contains <a href="http://www.linfo.org/information.html">information</a> about major <a href="http://www.linfo.org/filesystem.html"><i>filesystems</i></a> on the system. It takes its name from <i>file systems table</i>, and it is located in the <i>/etc</i> directory.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
The term <i>filesystem</i> can refer to a hierarchy of directories (also called a <a href="http://www.linfo.org/directory_tree.html"><i>directory tree</i></a>) that is used to organize files on a <a href="http://www.linfo.org/computer.html">computer</a> system. It can also refer to the <i>type</i> of filesystem, that is, how the <a href="http://www.linfo.org/storage.html">storage</a> of <a href="http://www.linfo.org/data.html">data</a> is organized (i.e., files, folders, etc.) on a computer disk (hard disk, floppy disk, <a href="http://www.linfo.org/cdrom.html">CDROM</a>, etc.) or on a <a href="http://www.linfo.org/partition.html"><i>partition</i></a> (i.e., a logically independent section) on a <a href="http://www.linfo.org/hdd.html">hard disk drive</a>
(HDD). Each type of filesystem has its own set of rules for controlling
the allocation of disk space to files and for associating each file
with its <a href="http://www.linfo.org/metadata.html"><i>metadata</i></a> (e.g., name, <i>permissions</i> and <a href="http://www.linfo.org/timestamp.html">timestamps</a>).
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
/etc/fstab is created automatically when the operating system is
installed, and it is modified automatically when changes are made to the
filesystems. It can also be modified by using specialized <a href="http://www.linfo.org/program.html">programs</a> or manually by using a <a href="http://www.linfo.org/text_editor.html">text editor</a>.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
The access permissions (i.e., the ability to read and modify) for
/etc/fstab are set by default to read-only for ordinary users as a
security and safety measure, and it is necessary to use the <a href="http://www.linfo.org/root.html"><i>root</i></a>
(i.e., administrative) account to modify it. This is because even a
small, unnoticed error could cause the system to malfunction, and repair
could be difficult for ordinary users. When modifying configuration
files such as /etc/fstab, it is important to make an emergency backup
copy, preferable on a separate HDD or on removable <a href="http://www.linfo.org/storage.html">storage</a> media (e.g., a floppy disk), prior to opening it in a text editor.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
/etc/fstab can be safely viewed by using the <a href="http://www.linfo.org/cat.html"><i>cat</i></a> <a href="http://www.linfo.org/command.html">command</a> (which is used to read text files) as follows:
</span></h4>
<h4>
</h4>
<blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><code>cat /etc/fstab</code></span>
</h4>
<h4>
</h4>
</blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
It can be seen that the content of the file is a six-column table, with
the columns separated by tabs or spaces. The columns are as follows:
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(1) The first column lists the physical location of each filesystem,
which can be a partition on the HDD or a separate device such as a CDROM
or floppy disk. Partitions are generally listed in the order in which
they are located on the HDD. If there are two HDDs, then all the
partitions on the first one are listed first. Which drive is considered
to be the first is defined in the computer's <a href="http://www.linfo.org/bios.html">BIOS</a> (basic input output system), which controls a computer's hardware while it is <a href="http://www.linfo.org/boot.html">booting</a> (i.e., starting up) and is usually stored in a <a href="http://www.linfo.org/flash_memory.html">flash memory</a> chip. Also, filesystems that are <i>mounted</i> (i.e., logically attached to the system) beneath other filesystems must follow their <i>parent</i> partitions.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
Any filesystem can be prevented from being automatically mounted during booting by <i>commenting out</i>
the line on which it is listed. This is accomplished by using a text
editor to add a hash symbol (#) to the beginning of the line. If at some
later date it is decided to again let that filesystem be automatically
mounted when the system boots up, all that is necessary is to remove the
hash symbol.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(2) The second column shows the <a href="http://www.linfo.org/mount_point.html"><i>mount point</i></a>, which is the directory in which the filesystem listed on that line is attached to the <a href="http://www.linfo.org/root_filesystem.html"><i>root filesystem</i></a>
(i.e., the main filesystem). Partitions that are located on removable
storage media are usually mounted as a sub-directory of the directory <a href="http://www.linfo.org/mnt.html"><i>/mnt</i></a>, such as <i>/mnt/floppy</i> for floppy disks and <i>/mnt/cdrom</i>
for CDROM drives. Some users may prefer to delete the /mnt directory
and create directories for devices on the root partition, with names
such as <i>/floppy</i> and <i>/cdrom</i>, in order to save time by typing in shorter <i>mount</i> commands. The mount command is used to manually mount filesystems and directories.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
In general, no attempt should be made to modify lines containing the <i>/proc</i> directory. /proc is a filesystem that is used to gather information for commands such as <a href="http://www.linfo.org/ps.html"><i>ps</i></a> and <a href="http://www.linfo.org/pstree.html"><i>pstree</i></a>, which report on <a href="http://www.linfo.org/process.html"><i>processes</i></a> currently on the system. A process is a running <a href="http://www.linfo.org/instance.html">instance</a> of a program.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(3) The third column shows the filesystem type with which each partition or device is formatted. Most modern Linux <a href="http://www.linfo.org/distributions_list.html">distributions</a>
(i.e., versions) support a large number of filesystem types, among the
most commonly used are ext2 (the basic Linux filesystem type), ext3 (an
enhanced version of ext2 with <i>journaling</i> capabilities), reiser
(another journaling filesystem), vfat (which is compatible with some
Microsoft filesystems), iso9660 (used by most CDROMs) and nfs (network
file system). The entry <i>swap</i> shows that the partition is used as <a href="http://www.linfo.org/swap_space.html"><i>swap space</i></a> (i.e., for <a href="http://www.linfo.org/virtual_memory.html">virtual memory</a>). The entry <i>udf</i> represents the <i>Universal Disk Format</i>) filesystem defined by the Optical Storage Technology Association, and is often used for CDROMs.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(4) The fourth column adds some basic security to the system by
designating by whom and how the filesystem or device can be used.
Numerous possible options are available, and any number of them can be
used, provided that they are separated with commas and do not conflict
with each other. Thus, the contents of this column for a partition or
device can become rather long and extend into the space under other
column headings.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
The inclusion of the term <i>user</i> indicates that ordinary users are allowed to mount the filesystem; if user is replaced by <i>nouser</i>, it means that only the root user can mount the filesystem. <i>owner</i> means that the owner of the device is allowed to mount it. <i>dev</i> permits any user to mount the filesystem.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><i>auto</i> means that the the system tries to detect the filesystem
type so that it can be mounted automatically when the computer is
started or when the <i>-a</i> <a href="http://www.linfo.org/option.html">option</a> (i.e., mount <i>all</i> filesystems mentioned in fstab) is used with the mount command. For auto to work, the <a href="http://www.linfo.org/kernel.html"><i>kernel</i></a> (i.e., the core of the operating system) must be <a href="http://www.linfo.org/compiler.html">compiled</a> to support the type of filesystem to be mounted. <i>noauto</i>
prevents the filesystem from being mounted when the computer starts,
even when the -a option is used with the mount command; thus, a
filesystem must be mounted manually (i.e., with the mount command) if it
is to be used. <i>ignore</i> means that the system does not try to
mount the partition or device; this is useful if it is desired to list
all partitions on the system for later reference and possible mounting
at some future date.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><i>ro</i> (read-only) allows users to read files on the filesystem but not modify them; <i>rw</i> (read-write) allows users to both read files on the filesystem and also write to them. <i>exec</i> lets users run <a href="http://www.linfo.org/executable.html"><i>executable files</i></a> (i.e., programs) on the filesystem; <i>no exec</i> prevents users from running executable files on the filesystem.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><i>suid</i> permits user or group identifiers to be used on the partition.
<i>nosuid</i> prevents user or group identifiers from being used.
<i>supermount</i>, which is used in Mandriva Linux, allows floppies and
CDROM disks to be replaced without the user having to unmount and
remount them.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
Red Hat and Fedora Linux include an option called <i>kudzu</i> for
removable media drives, which allows such drives to be automatically
added to and removed from /etc/fstab. This option can be deleted by the
root user if it is desired to permanently add the entry for the
corresponding removable media drive to /etc/fstab.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><i>async</i> indicates that all input and output to the filesystem or
device should be performed asynchronously, and it is the default because
of generally better performance. <i>sync</i> signifies that all input and output to the file system should be done synchronously.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><i>defaults</i> uses the default options, which are rw, suid, dev, exec,
auto, nouser and async. If it is desired for all users to be able to
use the partition or device freely, then this field should read: <i>user, auto, dev, exec, rw</i>.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(5) The fifth column is used to determine whether the <i>dump</i>
command will back up the filesystem. This column is rarely used and has
two options: 0, do not dump, which is used for most partitions, and 1,
dump, which is used for the root partition.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
(6) The sixth column is used by the <i>fsck</i> program to determine the
order in which the computer checks the filesystems when it boots. The
three possible values for the column are: 0, do not check, 1, check
first (only the root partition should have this setting) and 2, check
after the root partition has been checked. Most Linux distributions set
all the partitions to 0, except for the root partition. If maintenance
is important, 2 should be used, although this can increase the amount of
time required for booting.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
Because /etc/fstab defines how filesystems are mounted when starting the
computer, changes made to the file will not take effect until the
computer is restarted. It is read by the commands mount, <i>umount</i> (which unmounts filesystems), <i>swapon</i>
(which which enables devices and files for swapping) and fsck, and thus
it is important that all of its data be accurate and complete.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
One of the nice features of /etc/fstab is that it will fill in the
details for shortened mounting commands. For example, the command <i>mount /mnt/cdrom</i> can be used in place of the command <i>mount -t iso9660 -ro,noauto,owner, /dev/cdrom /mnt/cdrom</i>.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
/etc/fstab does not necessarily list all potentially available
partitions on the system, particularly if they are formatted for another
operating system. The full list of partitions that are available for
mounting can be seen by using the command <i>fdisk</i> as root and then typing the letter <i>p</i> and pressing the ENTER key. As the first HDD on a system is designated by <i>hda</i>, the following will list all available partitions on a system with a single HDD:
</span></h4>
<h4>
</h4>
<blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><code>/sbin/fdisk /dev/hda</code></span>
</h4>
<h4>
</h4>
</blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
In contrast to the Microsoft Windows operating systems, in which
partitions are labeled with letters, Linux gives each partition a
three-part name. Partitions (as well as devices and ports) are defined
in the <i>/dev</i> directory, thus each partition name starts with /dev. The first partition on a system is usually designated <i>/dev/hda1</i>. A partition that exists on another computer on the <a href="http://www.linfo.org/network.html">network</a> usually consists of the name of the <a href="http://www.linfo.org/host.html"><i>host</i></a> (i.e., other computer on the network) followed by a colon, a space and a directory name
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
Filesystems that are described in /etc/fstab are typically mounted when
the computer is booted, unless the noauto option is used. A list of
which filesystems are actually mounted can be seen by using the mount
command with no options and no <a href="http://www.linfo.org/argument.html"><i>arguments</i></a> (i.e., input data), that is,
</span></h4>
<h4>
</h4>
<blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><code>mount</code></span>
</h4>
<h4>
</h4>
</blockquote>
<h4>
</h4>
<h4>
<span style="color: #cc0000;">
Additional filesystems (i.e., those listed by fdisk) can be mounted
immediately by using mount with the appropriate options and arguments.
They can also be mounted at the next boot by modifying or adding entries
to /etc/fstab.
</span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><br /></span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><br /></span></h4>
<h4>
</h4>
<h4>
<span style="color: #cc0000;"><br /></span></h4>
<h4>
<span style="color: #cc0000;"><br /></span></h4>
</td><td width="10%"><h4>
<span style="color: #cc0000;"><br /></span></h4>
</td></tr>
</tbody></table>
<span style="color: #cc0000;">
</span></div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-62013472898222408472014-02-28T01:33:00.004-08:002014-02-28T01:33:45.861-08:00File Compression and Archiving with Gzip, Zip, and Tar<div dir="ltr" style="text-align: left;" trbidi="on">
<h1 class="SECT1" style="color: red;">
<a href="https://www.blogger.com/blogger.g?blogID=3244256980262892361" name="S1-ZIP-TAR"><br /></a></h1>
<div class="SECT2" style="color: #6aa84f;">
<h2 class="SECT2" style="color: red;">
<a href="https://www.blogger.com/blogger.g?blogID=3244256980262892361" name="S1-GZIP-ZIP">Compressing with Gzip and Zip</a></h2>
Compressed files use less disk space and download faster than large,
uncompressed files. You can compress Linux files with the open-source
compression tool <b class="APPLICATION">Gzip</b> or with <b class="APPLICATION"> Zip</b>, which is recognized by most operating systems.
<br />
By convention, compressed files are given the extension<tt class="FILENAME"> .gz</tt>. The command <tt class="USERINPUT"><b>Gzip</b></tt> creates a
compressed file ending with <tt class="FILENAME">.gz</tt>;
<tt class="USERINPUT"><b>Gunzip</b></tt> extracts the compressed files and
removes the <tt class="FILENAME">.gz</tt> file.
<br />
To compress a file, at a shell prompt, type the following command:
<br />
<table bgcolor="#e0e0e0" border="0" style="width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">gzip filename.ext</tt></pre>
</td></tr>
</tbody></table>
The file will be compressed and saved as
<tt class="FILENAME">filename.ext.gz</tt>.
<br />
To expand a compressed file, type:
<br />
<table bgcolor="#e0e0e0" border="0" style="width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">gunzip filename.ext.gz</tt></pre>
</td></tr>
</tbody></table>
The <tt class="FILENAME">filename.ext.gz</tt> is deleted and replaced with
<tt class="FILENAME">filename.ext</tt>.
<br />
If you exchange files with non-Linux users, you may want to use
<tt class="USERINPUT"><b>zip</b></tt> to avoid compatibility problems. Red Hat Linux can
easily open zip or gzip files, but non-Linux operating systems may
have problems with gzip files.
<br />
To compress a file with <tt class="USERINPUT"><b>zip</b></tt>, type the following:
<br />
<table bgcolor="#e0e0e0" border="0" style="width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">zip -r filename.zip files</tt></pre>
</td></tr>
</tbody></table>
In this example, <i class="EMPHASIS">filename</i> represents the file you
are creating and <i class="EMPHASIS">files</i> represents the files you
want to put in the new file:
<br />
To extract the contents of a zip file, type:
<br />
<table bgcolor="#e0e0e0" border="0" style="width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">unzip filename.zip</tt></pre>
</td></tr>
</tbody></table>
You can zip or gzip multiple files at the same time. List the files
with a space between each one.
<br />
<table bgcolor="#e0e0e0" border="0" style="width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">gzip filename.gz file1 file2 file3 /user/work/school </tt></pre>
</td></tr>
</tbody></table>
The above command will compress <tt class="FILENAME">file1</tt>,
<tt class="FILENAME">file2</tt>, <tt class="FILENAME"> file3</tt>, and the
contents of the <tt class="FILENAME">/user/work/school</tt> directory and
put them in <tt class="FILENAME">filename.gz</tt>.
</div>
<h2 class="SECT2" style="color: #6aa84f;">
<a href="https://www.blogger.com/blogger.g?blogID=3244256980262892361" name="S2-TAR">Archiving with Tar</a></h2>
<div style="color: #6aa84f;">
Tar files place several files or the contents of a directory or directories
in one file. This is a good way to create backups and
archives. Usually, tar files end with the <tt class="FILENAME">.tar</tt>
extension.
</div>
<div style="color: #6aa84f;">
To create a tar file, type:
</div>
<table bgcolor="#e0e0e0" border="0" style="color: #6aa84f; width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">tar -cvf filename.tar files/directories</tt></pre>
</td></tr>
</tbody></table>
<div style="color: #6aa84f;">
In this example, <tt class="FILENAME">filename.tar</tt> represents the file
you are creating and <tt class="FILENAME">files/directories</tt> represents
the files or directories you want to put in the new file.
</div>
<div style="color: #6aa84f;">
You can use absolute or relative pathnames for these files and
directories (for more on pathnames, see <a href="https://www.centos.org/docs/2/rhl-gsg-en-7.2/s1-navigating-cd.html">the section called <i>Changing Directories with cd</i> in Chapter 10</a>). Separate the names of files and
directories with a space.
</div>
<div style="color: #6aa84f;">
The following input would create a tar file using absolute pathnames:
</div>
<table bgcolor="#e0e0e0" border="0" style="color: #6aa84f; width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"> <tt class="COMMAND"> tar -cvf foo.tar /home/mine/work /home/mine/school</tt>
</pre>
</td></tr>
</tbody></table>
<div style="color: #6aa84f;">
The above command would place all the files in the
<tt class="FILENAME">/work</tt> subdirectory and the /school subdirectory
in a new file called <tt class="FILENAME">foo.tar</tt> in the current
working directory.
</div>
<div style="color: #6aa84f;">
The command <tt class="USERINPUT"><b>tar -cvf foo.tar file1.txt file2.txt
file3.txt</b></tt> would place <tt class="FILENAME">file1.txt</tt>,
<tt class="FILENAME">file2.txt</tt> and <tt class="FILENAME">file3.txt</tt> in
a new file called <tt class="FILENAME">foo.tar</tt>.
</div>
<div style="color: #6aa84f;">
To list the contents of a tar file, type:
</div>
<table bgcolor="#e0e0e0" border="0" style="color: #6aa84f; width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"> <tt class="COMMAND">tar -tvf foo.tar</tt></pre>
</td></tr>
</tbody></table>
<div style="color: #6aa84f;">
To extract the contents of a tar file, type:
</div>
<table bgcolor="#e0e0e0" border="0" style="color: #6aa84f; width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">tar -xvf foo.tar</tt></pre>
</td></tr>
</tbody></table>
<div style="color: #6aa84f;">
This command does not remove the <tt class="FILENAME">.tar</tt> file, but
it places copies of the <tt class="FILENAME">.tar</tt> contents in the
current working directory.
</div>
<div style="color: #6aa84f;">
The <tt class="USERINPUT"><b>tar</b></tt> command does not compress
files automatically. You can compress tar files with:
</div>
<table bgcolor="#e0e0e0" border="0" style="color: #6aa84f; width: 100%px;"><tbody>
<tr><td><pre class="SCREEN"><tt class="COMMAND">tar -czvf foo.tar</tt></pre>
</td></tr>
</tbody></table>
<div style="color: #6aa84f;">
Compressed tar files are conventionally given the extension
<tt class="FILENAME">.tgz</tt> and are compressed with gzip.
</div>
<div style="color: #6aa84f;">
To expand a compressed tar file type:
</div>
<pre class="SCREEN" style="color: #6aa84f;"><tt class="COMMAND">tar -xzvf foo.tgz</tt></pre>
</div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-56854295320523616722014-02-18T21:50:00.001-08:002014-02-18T21:50:47.287-08:00Data Recovery Weekly: raid5<a href="http://data-recovery-weekly.blogspot.com/search/label/raid5#.UwRGJvcsE-Y.blogger">Data Recovery Weekly: raid5</a>Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-77770113011782184232014-02-18T21:48:00.001-08:002014-02-18T21:48:45.231-08:00Data Recovery Weekly: On RAID computational requirements<a href="http://data-recovery-weekly.blogspot.com/2010/11/on-raid-computational-requirements.html#.UwRFXpmRefc.blogger">Data Recovery Weekly: On RAID computational requirements</a>Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-86155939191685070232014-02-13T03:36:00.001-08:002014-02-13T03:38:45.370-08:00Welcome to my blog!!!<div dir="ltr" style="text-align: left;" trbidi="on">
<h3 class="post-title entry-title" itemprop="name" style="color: black;">
<br /></h3>
<div class="post-header" style="color: black;">
</div>
<div style="color: black;">
<span style="font-size: 100%;">Warm welcome to all linux newbies.. You
will find a lot of interesting stuffs here which you can understand
easily. Experienced guys please excuse..This is just a beginners
guide....:)</span></div>
<div style="color: black;">
<span style="font-size: 100%;"><br /></span></div>
<div style="color: black;">
<span style="font-size: 100%;"><br /></span></div>
<div style="color: black;">
<span style="font-size: 100%;"><br /></span></div>
<h2 class="date-header" style="color: black;">
</h2>
<div class="date-posts" style="color: black;">
<div class="post-outer">
<div class="post hentry uncustomized-post-template" itemprop="blogPost" itemscope="itemscope" itemtype="http://schema.org/BlogPosting">
<a href="https://www.blogger.com/blogger.g?blogID=3244256980262892361" name="7491051586461104382"></a>
<h3 class="post-title entry-title" itemprop="name">
Cron jobs tutorial for beginners
</h3>
<div class="post-header">
</div>
<div class="post-body entry-content" id="post-body-7491051586461104382" itemprop="description articleBody">
<div style="text-align: justify;">
Cron is a utility that allows tasks to
be automatically run in the background at regular intervals by the cron
daemon. These tasks are often termed as cron jobs. Crontab (CRON TABle)
is a file which contains the schedule of cron entries to be executed at
specified times.</div>
<br />
<span style="font-weight: bold;">commands:</span><br />
<br />
crontab filename Install filename as your crontab file.<br />
crontab -e --> Edit your crontab file.<br />
crontab -l --> Show your crontab file.<br />
crontab -r --> Remove your crontab file.<br />
crontab -v --> Display the last time you edited your crontab file<br />
<br />
<div style="text-align: justify;">
Inorder
to setup a cron you just need to specify the task and the time at which
it should be executed. Definitely it should be in the format as below.
It can be a little tough at the beginning, but will be much easier if
you learn how to specify the time at which a particular task should be
executed. Workout with examples to get more idea about cron jobs.</div>
<br />
<span style="font-weight: bold;">Crontab syntax :-</span><br />
<br />
<div style="text-align: justify;">
A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.</div>
<br />
* * * * * command to be executed<br />
- - - - -<br />
| | | | |<br />
| | | | +----- day of week (0 - 6) (Sunday=0)<br />
| | | +------- month (1 - 12)<br />
| | +--------- day of month (1 - 31)<br />
| +----------- hour (0 - 23)<br />
+------------- min (0 - 59)<br />
<br />
ie,<br />
minute hour day month day-of-week command-line-to-execute<br />
0-59 0-23 1-31 1-12 0-7<br />
<br />
In a linux server you can find cron entry for a user at /var/spool/cron/username<br />
<br />
<br />
<span style="font-weight: bold;">examples:</span><br />
<br />
if you want a certain command to run at 5.30 am, you will have to code it as:<br />
30 5 * * * command to execute<br />
<br />
If you want something run at 8 pm everyday, it has to be coded as:<br />
0 20 * * * command to execute (20 is 8 pm in the 24-hour time format)<br />
<br />
If you want to set the cron job every sunday at midnight 11.30 PM<br />
30 23 * * 0 command to execute (0--represents the Sunday)<br />
<br />
If you want to run the task at 1am and 2am only from Monday to Friday:<br />
* 1,2 * * 1-5 command to execute<br />
<br />
If you want to execute a cronjob at 4 am every Sunday:<br />
00 4 * * 0 command to execute<br />
<br />
To execute a cronjob at 4:42 am every 1st of the month<br />
42 4 1 * * command to execute<br />
<br />
Cron also supports <span style="font-weight: bold;">'step'</span> values.<br />
<div style="text-align: justify;">
A
value of */2 in the date of month field means that the command runs
every two days and */5 in the hours field would mean the command runs
every 5 hours.</div>
<br />
Difference between */5 * * * * and 5 * * * *<br />
<br />
*/5 * * * * command to execute -->> This will execute the cronjob in every 5<br />
minutes.<br />
<br />
<div style="text-align: justify;">
5 * * * * command to execute -->> This will execute cron job in 5th minute of every hour</div>
<br />
<br />
<div style="text-align: justify;">
If both the day of month and day of week are specified, the command will be executed when either of the events happen.</div>
<div style="text-align: justify;">
* 12 16 * 1 command to execute -->> command will be executed on every Monday and every 16th</div>
<br />
<div style="text-align: justify;">
Cron also accepts <span style="font-weight: bold;">lists</span> in the fields. Lists can be in the form, 1,2,3 (meaning 1 and 2 and 3) or 1-3 (also meaning 1 and 2 and 3)</div>
<div style="text-align: justify;">
59
11 * * 1,2,3,4,5 command to execute -->> will execute the command
at 11:59 Monday, Tuesday, Wednesday, Thursday and Friday</div>
<br />
<br />
to be continued...<br />
<br />
ref:<br />
http://www.unixgeeks.org/security/newbie/unix/cron-1.html<br />
http://en.wikipedia.org/wiki/Cron<br />
http://www.aota.net/Script_Installation_Tips/cronhelp.php3<br />
http://www.thesitewizard.com/general/set-cron-job.shtml<br />
https://www.simplehelix.com/hosting/knowledgebase.php?action=displayarticle&catid=4&id=77
</div>
</div>
</div>
</div>
</div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-76143009685311609542014-02-12T02:23:00.001-08:002014-02-12T02:23:12.364-08:00IP Tables<div dir="ltr" style="text-align: left;" trbidi="on">
<i><b> <span style="color: blue;"> Basic iptables Syntax</span></b></i><br />
<div style="color: blue;">
</div>
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<br />Firewalls built with Netfilter are built through the iptables firewall administration command.<br />The iptables command implements the firewall policies that you create and manages the<br />behavior of the firewall. Netfilter firewalls have three individual tables: filter, NAT, and man-<br />gle. Within these tables, firewalls are built through chains, with each individual link in the<br />chain being an individual iptables command.<br />Within the default filter table there is a chain for input or data coming into the firewall, a<br />chain for output or data leaving the firewall, a chain for forwarding or data being sent through<br />the firewall, and other chains including chains named and configured by the user, commonly<br />(and appropriately) called user-defined chains. The NAT and mangle tables have specialty<br />chains that will be discussed later. For now, it’s sufficient to know that the filter table is the<br />default table for implementing a basic firewall, the NAT table is used to provide NAT and<br />related functions, and the mangle table is used when the packet will be altered by the firewall.<br />iptables commands are issued with very specific syntax. Many times, the ordering of the<br />options given to iptables makes the difference between a successful command and a syntax<br />error. The commands issued to iptables fall through, so a command that allows certain pack-<br />ets that follows a command that denies those same packets will cause the data to be dropped<br />by the firewall.<br />The basic syntax for an iptables command begins with the iptables command itself, followed<br />by one or more options, a chain, a set of match criteria, and a target or disposition. The layout<br />of the command largely depends on the action to be performed. Consider this syntax:<br />iptables <option> <chain> <matching criteria> <target><br />In building a firewall, the option is usually -A to append a rule onto the end of the ruleset.<br />Naturally, there are several options depending on the target and the operation being per-<br />formed. This chapter covers most of those options.<br />As previously stated, the chain can be an input chain, an output chain, a forwarding chain, or<br />a user-defined chain. In addition, the chain might also be a specialty chain contained in the<br />NAT or mangle tables.<br /></div>
Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0tag:blogger.com,1999:blog-3244256980262892361.post-27431747327591008892014-02-11T22:26:00.001-08:002014-02-11T22:26:13.716-08:00Linux access control using TCP WRAPPERS<a href="http://www.slashroot.in/linux-access-control-using-tcp-wrappers#.UvsT8TSqT2g.blogger">Linux access control using TCP WRAPPERS</a>Anonymoushttp://www.blogger.com/profile/16728030206340096655noreply@blogger.com0