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Helo command rejected: need fully-qualified hostname

I got this error when I tried to send an email to a local user  using outlook express, and as an unauthorized person. If I check the option “my server needs authentication” on, and input the correct account information that

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How to debug Postfix?

If you’ve read about my tutorial on setting up Postfix, you should be able to send and receive emails now. But life never goes smooth always.  You may encounter this or that problem in using the email system. To solve

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A strange reason that causes httpd dead

Today, my website is down.

This problem persists even I restart httpd. I have to look into the apache log to investigate what happened. Where is the apache log? I know the location of the error/access log for the

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generate certification using openssl

Certification is frequently used in secure communication such as https and smtps. Certification contains the subject information and its public key, and a signature. The signature is generated by encrypting the hash of   the subject information and its public

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How to use openssl to send emails?

Sure, you can use an email client such as outlook to send emails, but openssl can help you debug the problems when you set up/configure your own email system. After issuing the following command,

  You can see the

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How to install and configure Postfix on CentOS?

I like digitalocean’s tutorials about setting up servers and VPS, which is usually easy to understand, and if not (like this Postfix tutorial), at least works! I composed a tutorial about setting up sendmail. In that tutorial, you can see

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the difference between redirection and rewrite

If you wrote rewrite rules, you may get confused by the rewrite and redirection. What happens if you write the following RewriteRules?

If you type , the browser will display the content of test3.html while the url in

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stdout/stderr redirection

You must know the standout redirection: ls > file The output of ls is now saved in file “file”. This is equivalent to: ls 1>file Note that there is no space between 1 and >. 1 is the file descriptor

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How to upgrade mysql on CentOS6?

On CentOS6, the version of  mysql is typically V5.1. mysql -V mysql  Ver 14.14 Distrib 5.1.73, for redhat-linux-gnu (x86_64) using readline 5.1 rpm -q mysql mysql-5.1.73-7.el6.x86_64 rpm -qa|grep mysql mysql-libs-5.1.73-7.el6.x86_64 php-mysql-5.3.3-47.el6.x86_64 mysql-5.1.73-7.el6.x86_64 mysql-server-5.1.73-7.el6.x86_64 Sometimes you may want to upgrade mysql

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How to temporally disable a website?

Sometimes you may want to temporally shut down your website to do some maintenance work. Stopping the httpd service may not be a good choice for you because you have other websites on the same host. You may think you

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