How do I check the health of my 3ware RAID array?

3ware allows for a browser interface to be used, however unless accessed locally this can be a security risk. Therefore we suggest using the command line interface if at all possible.

You need to download the 3ware CLI utilities from the vendor website or from your datacenter portal. Installation is as simple as unzipping the file into a separate folder. Please note you MUST be root/administrator to run the utility.

Quick command reference for 3ware CLI tools

These devices must be followed by a number denoting which is being queried.

tw_cli /c0 show (Output shows information needed to know the health of the RAID array)

./tw_cli /c1 show


Unit  UnitType  Status         %Cmpl  Stripe  Size(GB)  Cache  AVerify  IgnECC


u0    RAID-5    OK             –      64K     465.641   OFF    OFF      OFF

Port   Status           Unit   Size        Blocks        Serial


p0     OK               u0     233.76 GB   490234752     WD-WCANY1727093

p1     OK               u0     233.76 GB   490234752     WD-WCANY1622544

p2     OK               u0     233.76 GB   490234752     WD-WCANY1657267

p3     NOT-PRESENT      –      –           –             –

*note the following:

c = controller
Controller can be 0 or 1
u = unit
Unit number depends on number arrays. It is 0 in most cases.
p = port
Port denotes port number. In most cases, it is 0-4.


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How to Optimize MySQL

There is a default my.cnf that comes with mysql (4+5) that will make mysql run a bit quicker if you have 2+ gig of ram cp -f /usr/share/mysql/my-large.cnf /etc/my.cnfThere is also my-huge.cnf, or my-medium.cnf depending on your hardware setup.   Check the contents of these my*.cnf files for the one that’s right for you.

*NOTE* the log-bin option is enabled  by default.  This will quickly use a lot of disk space.  It’s recommended to comment out the log-bin line from your /etc/my.cnf, if it exists.


Remember to restart mysql when you are done with your my.cnf tweaking:

Redhat:/sbin/service mysqld restart

FreeBSD:/usr/local/etc/rc.d/mysqld restart

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Linux is just the kernel, GNU is the OS.

This is an interesting read and some old history copied from

Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called “Linux”, and many of its users are not aware that it is basically the GNU system, developed by the GNU Project.

There really is a Linux, and these people are using it, but it is just a part of the system they use. Linux is the kernel: the program in the system that allocates the machine’s resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called “Linux” distributions are really distributions of GNU/Linux.

Many users do not understand the difference between the kernel, which is Linux, and the whole system, which they also call “Linux”. The ambiguous use of the name doesn’t help people understand. These users often think that Linus Torvalds developed the whole operating system in 1991, with a bit of help.

Programmers generally know that Linux is a kernel. But since they have generally heard the whole system called “Linux” as well, they often envisage a history that would justify naming the whole system after the kernel. For example, many believe that once Linus Torvalds finished writing Linux, the kernel, its users looked around for other free software to go with it, and found that (for no particular reason) most everything necessary to make a Unix-like system was already available.

What they found was no accident—it was the not-quite-complete GNU system. The available free software added up to a complete system because the GNU Project had been working since 1984 to make one. In the The GNU Manifesto we set forth the goal of developing a free Unix-like system, called GNU. The Initial Announcement of the GNU Project also outlines some of the original plans for the GNU system. By the time Linux was started, GNU was almost finished.

Most free software projects have the goal of developing a particular program for a particular job. For example, Linus Torvalds set out to write a Unix-like kernel (Linux); Donald Knuth set out to write a text formatter (TeX); Bob Scheifler set out to develop a window system (the X Window System). It’s natural to measure the contribution of this kind of project by specific programs that came from the project.

If we tried to measure the GNU Project’s contribution in this way, what would we conclude? One CD-ROM vendor found that in their “Linux distribution”, GNU software was the largest single contingent, around 28% of the total source code, and this included some of the essential major components without which there could be no system. Linux itself was about 3%. (The proportions in 2008 are similar: in the “main” repository of gNewSense, Linux is 1.5% and GNU packages are 15%.) So if you were going to pick a name for the system based on who wrote the programs in the system, the most appropriate single choice would be “GNU”.

But that is not the deepest way to consider the question. The GNU Project was not, is not, a project to develop specific software packages. It was not a project to develop a C compiler, although we did that. It was not a project to develop a text editor, although we developed one. The GNU Project set out to develop a complete free Unix-like system: GNU.

Many people have made major contributions to the free software in the system, and they all deserve credit for their software. But the reason it is an integrated system—and not just a collection of useful programs—is because the GNU Project set out to make it one. We made a list of the programs needed to make a complete free system, and we systematically found, wrote, or found people to write everything on the list. We wrote essential but unexciting (1) components because you can’t have a system without them. Some of our system components, the programming tools, became popular on their own among programmers, but we wrote many components that are not tools (2). We even developed a chess game, GNU Chess, because a complete system needs games too.

By the early 90s we had put together the whole system aside from the kernel. We had also started a kernel, the GNU Hurd, which runs on top of Mach. Developing this kernel has been a lot harder than we expected; the GNU Hurd started working reliably in 2001, but it is a long way from being ready for people to use in general.

Fortunately, we didn’t have to wait for the Hurd, because of Linux. Once Torvalds freed Linux in 1992, it fit into the last major gap in the GNU system. People could thencombine Linux with the GNU system to make a complete free system — a version of the GNU system which also contained Linux. The GNU/Linux system, in other words.

Making them work well together was not a trivial job. Some GNU components(3) needed substantial change to work with Linux. Integrating a complete system as a distribution that would work “out of the box” was a big job, too. It required addressing the issue of how to install and boot the system—a problem we had not tackled, because we hadn’t yet reached that point. Thus, the people who developed the various system distributions did a lot of essential work. But it was work that, in the nature of things, was surely going to be done by someone.

The GNU Project supports GNU/Linux systems as well as the GNU system. The FSF funded the rewriting of the Linux-related extensions to the GNU C library, so that now they are well integrated, and the newest GNU/Linux systems use the current library release with no changes. The FSF also funded an early stage of the development of Debian GNU/Linux.

Today there are many different variants of the GNU/Linux system (often called “distros”). Most of them include non-free software—their developers follow the philosophy associated with Linux rather than that of GNU. But there are also completely free GNU/Linux distros. The FSF supports computer facilities for two of these distributions, Ututoand gNewSense.

Making a free GNU/Linux distribution is not just a matter of eliminating various non-free programs. Nowadays, the usual version of Linux contains non-free programs too. These programs are intended to be loaded into I/O devices when the system starts, and they are included, as long series of numbers, in the “source code” of Linux. Thus, maintaining free GNU/Linux distributions now entails maintaining a free version of Linux too.

Whether you use GNU/Linux or not, please don’t confuse the public by using the name “Linux” ambiguously. Linux is the kernel, one of the essential major components of the system. The system as a whole is basically the GNU system, with Linux added. When you’re talking about this combination, please call it “GNU/Linux”.

If you want to make a link on “GNU/Linux” for further reference, this page and are good choices. If you mention Linux, the kernel, and want to add a link for further reference, is a good URL to use.

Addendum: Aside from GNU, one other project has independently produced a free Unix-like operating system. This system is known as BSD, and it was developed at UC Berkeley. It was non-free in the 80s, but became free in the early 90s. A free operating system that exists today(4) is almost certainly either a variant of the GNU system, or a kind of BSD system.

People sometimes ask whether BSD too is a version of GNU, like GNU/Linux. The BSD developers were inspired to make their code free software by the example of the GNU Project, and explicit appeals from GNU activists helped persuade them, but the code had little overlap with GNU. BSD systems today use some GNU programs, just as the GNU system and its variants use some BSD programs; however, taken as wholes, they are two different systems that evolved separately. The BSD developers did not write a kernel and add it to the GNU system, and a name like GNU/BSD would not fit the situation.(5)


  1. These unexciting but essential components include the GNU assembler, GAS and the linker, GLD, both are now part of the GNU Binutils package, GNU tar, and more.
  2. For instance, The Bourne Again SHell (BASH), the PostScript interpreter Ghostscript, and the GNU C library are not programming tools. Neither are GNUCash, GNOME, and GNU Chess.
  3. For instance, the GNU C library.
  4. Since that was written, a nearly-all-free Windows-like system has been developed, but technically it is not at all like GNU or Unix, so it doesn’t really affect this issue. Most of the kernel of Solaris has been made free, but if you wanted to make a free system out of that, aside from replacing the missing parts of the kernel, you would also need to put it into GNU or BSD.
  5. On the other hand, in the years since this article was written, the GNU C Library has been ported to several versions of the BSD kernel, which made it straightforward to combine the GNU system with that kernel. Just as with GNU/Linux, these are indeed variants of GNU, and are therefore called, for instance, GNU/kFreeBSD and GNU/kNetBSD depending on the kernel of the system. Ordinary users on typical desktops can hardly distinguish between GNU/Linux and GNU/*BSD.
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Can I add more RAM to my 32 bit Operating System (OS)?

Some 32 bit Operating Systems (OS) limit the amount of RAM they will support. Exceeding that limit may contribute to a number of problems. Therefore it is not supported. Upgrading to a 64 bit Operating Systems (OS) is recommended. A list of 32 bit Operating Systems (OS) with limited RAM is below.


Operating System (OS)


RAM Limit (GB)

CloudLinux 5 32 bit 64
CloudLinux 6 32 bit 8
Debian 6 32 bit 32
RHEL/CentOS 5 Minimal/LAMP 32 bit 64
RHEL/CentOS 6 Minimal/LAMP 32 bit 16
Ubuntu 8.04 LTS 32 bit 64
Ubuntu 10.04 LTS 32 bit 64
Ubuntu 12.04 LTS 32 bit 64

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How to generate a Strong Password


Creating and using strong passwords is an important part of your server security.


If your old password was compromised, make sure that your new password is very different from your old one.

Things to include

  1. At least eight characters.
  2. One or more of each of the following:
    • lower-case letter
    • upper-case letter
    • number
    • punctuation mark
  3. Lookalike characters to protect against password glimpses. Examples:
    • O as in Oscar and the number 0.
    • Lower-case l and upper-case I.
    • The letter S and the $ sign.

Things to avoid

  1. Words you can find in the dictionary.
  2. Passwords shown as “example strong passwords.”
  3. Personal information, such as names and birth dates.
  4. Keyboard patterns, like qwerty or 12345. Particularly avoid sequences of numbers in order.
  5. Common acronyms.
  6. All one type of character – such as all numbers, all upper-case letters, all lower-case letters, etc.
  7. Repeating characters, such as mmmm3333.
  8. The same password you use for another application.

Memorable password tips

While passwords that are easy for you to remember are also less secure than a completely random password, following these tips can help you find the right balance between convenience for you and difficulty for hackers.

  1. Create a unique acronym for a sentence or phrase you like.
  2. Include phonetic replacements, such as ‘Luv 2 Laf’ for ‘Love to Laugh.’
  3. Jumble together some pronounceable syllables, such as ‘iv,mockRek9.’

Keep your password secret

  1. Never tell your password to anyone (this includes significant others, roommates, coworkers, etc.). If you need to grant someone access to your server, set up a separate username and password for that person.
  2. Never write your password down, especially not anywhere near your computer.
  3. Do not store your password in a plain text file on your computer.
  4. Never send your password over an unecrypted connection – including unencrypted email.
  5. Periodically test your current password.
  6. Update your password every six months.

Third-party tools

Password generators

Password strength tests

Password storing tools

CentOS Linux PHP Tutorials Web Applications

How To: Install memcached on CentOS 6

Memcached is a distributed, high-performance, in-memory caching system that is primarily used to speed up sites that make heavy use of databases. It can however be used to store objects of any kind. Nearly every popular CMS has a plugin or module to take advantage of memcached, and many programming languages have a memcached library, including PHP, Perl, Ruby, and Python. Memcached runs in-memory and is thus quite speedy, since it does not need to write to disk. Here’s how to install it on CentOS 6:


Memcached does have some dependencies that need to be in place. Install libevent using yum:

yum install libevent libevent-devel

The memcached install itself starts with

To start installing memcached, change your working directory to /usr/local/src and download the latest memcached source:

cd /usr/local/src

Uncompress the tarball you downloaded and change into the directory that is created:

tar xvzf memcached-1.4.15.tar.gz
cd memcached-1.4.15

Memcached is actively developed, so the version used in this tutorial may be out of date by the time you read this. As of this writing, 1.4.15 is the latest stable version. Check for a newer version before proceeding with the installation.

Next, configure your Makefile. The simplest way is to run:


Additional configure flags are available and can improve performance if your server is capable. For 64-bit OSes, you can enable memcached to utilize a larger memory allocation than is possible with 32-bit OSes:

./configure --enable-64bit

If your server has multiple CPUs or uses multi-core CPUs, enable threading:

./configure --enable-threads

If your server supports it, you can use both flags:

./configure --enable-threads --enable-64bit

n.b.: if the configure script does not run, you may have to install compiling tools on your server. That is as simple as

yum install gcc
yum install make

Once the configure script completes, build and install memcached:

make && make install

Last but not least, start a memcached server:

memcached -d -u nobody -m 512 -p 11211

Put another way, the previous command can be laid out like this:

memcached -d -u [user] -m [memory size] -p [port] [listening IP]

Let’s go over what each switch does in the above command:

Tell memcached to start up as a backgrounded daemon process
Specify the user that you want to run memcached
Set the memory that you want to be allocated my memcached
The port on which memcached will listen.


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Hotlink protection: How-To prevent people from stealing your files


Create an .htaccess file in your public_html directory with the following code:

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www.)?*$ [NC]
RewriteRule .(gif|jpg)$ – [F]

Where is your domain.


Control Panels DirectAdmin MySQL Tutorials

How to upgrade mysql with custombuild

To upgrade mysql using the custombuild script, do the following:

cd /usr/local/directadmin/custombuild
./build set mysql 5.1
./build set mysql_inst yes
./build set mysql_backup yes
./build update
./build mysql

Where mysql can be 5.0, 5.1 or 5.5.

A full raw sql backup will be run prior to the upgrade if you have mysql_backup=yes set.  It goes without saying, always make backups, either with this tool, or with other means.

After the mysql update, always recompile php.

./build php n

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Why do I need an owned IP for my own SSL certificate?

The reason you must have your own dedicated IP address when you want to use your own SSL certificate (when you don’t want the server wide shared certificate) is because of the way SSL and Apache (httpd) works.

For name based web-hosting (when many domains are on one IP) the web browser will pass the name of the domain being requested inside the httpd headers along with the request.  This way, Apache knows which domain you are trying to access even though there are many domains on that one IP address.

When you do the same thing through an SSL connection, the connection has to be made *before* the request can be sent.  In this connection, the certificate is passed.  The only information that Apache knows before the request is made is which IP the connection is being made to.  It has to be able to know which certificate to send before the request is made, thus you can’t use multiple certificates on the same IP (if you do, Apache will use the first certificate listed which DA will always set to the server shared certificate for shared IPs).

If you want to use your own certificate, it must be the first certificate listed.  This wouldn’t work for a shared IP, because there would multiple domain wanting this status, and the first certificate would the one shown.  For this reason the shared certificate is always used on a shared IP.  For your certificate, DA will acknowledge the IP as being ‘owned’ and will remove the server shared certificate as the first cert to be loaded, thus your certificate will be loaded instead.

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How To Clear Your DNS Cache

Windows® 8


  1. Press Win+X to open the WinX Menu.
  2. Right-click on Command Prompt and select Run as Administrator.
  3. Type the following command and press Enteripconfig /flushdns
  4. If the command was successful, you will see the following message:
    Windows IP configuration successfully flushed the DNS Resolver Cache.


Windows 7


  1. Click the Start button.
  2. Enter cmd in the Start menu search field.
  3. Right-click on Command Prompt and select Run as Administrator.
  4. Type the following command and press Enteripconfig /flushdns
  5. If the command was successful, you will see the following message:
    Windows IP configuration successfully flushed the DNS Resolver Cache.


Windows XP, 2000, or Vista®


  1. Click the Start button.
  2. On the Start menu, click Run….
    • If you do not see the Run command in Vista, enter run in the Search bar.
  3. Type the following command in the Run text box: ipconfig /flushdns


MacOS® 10.7 and 10.8


  1. Click Applications.
  2. Click Utilities.
  3. Double-click the Terminal application.
  4. Type the following command:
    sudo killall -HUP mDNSResponder

    Warning: To run this command, you will need to know the computer’s Admin account password.


MacOS 10.5 and 10.6


  1. Click Applications.
  2. Click Utilities.
  3. Double-click the Terminal application.
  4. Type the following command: sudo dscacheutil -flushcache