Category Archives: Apache

No space left on device.

Sometimes we can be fooled by error messages. For example one sunny day you see that for some reason your web or mail server doesn’t work. So you go to check the logs and find something similar to this:

2016/12/28 09:02:37 [crit] 24668#24668: *472674 open() "/var/cache/nginx/client_temp/0020878597" failed (28: No space left on device), client:, server:, request: "GET /cart/add/uenc/aHR0cDovL3d3dy5hYmNob21lLmNvbS9zaG9wL2xvdi1vcmdhbmljLWxvdi1pcy1iZWF1dGlmdWwtdGVh/product/19471/form_key/N8l3OyVkC1el9T8q/?product=19471&related_product=& HTTP/1.1", host: "", referrer: ""

Then when you check the free space you see that you have more than enough, and all kind of irrational thoughts start flowing into your mind, when it is the simple inodes space.

Usually it is just that there is not enough inodes left free on your files system, simple as that, but is easy to overlook as for some people this doesn’t happen often (and it shouldn’t).

[root@hostname client_temp]# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/mapper/os-root 1703936 1703103 833 100% /
tmpfs 1524264 4 1524260 1% /dev/shm
/dev/sda1 51000 50 50950 1% /boot
/dev/mapper/os-tmp 131072 2155 128917 2% /tmp
19660800 578302 19082498 3% /data

Apachebench Tutorial ab testing Tool Example in Ubuntu/Linux

Official Apache Page

Is there a time when you are thinking how to do a server load testing to evaluate your PHP web application performance? This is where you will be using the Apachebench or “ab” testing tool. This is a very useful open source tool not only to PHP developers but to the entire users of the Apache server. This tool is used to evaluate the execution times of your PHP web application or the response time of your website under “stressing” conditions. This condition means how your PHP web application will perform under conditions similar to what exactly will be happening on a real web server not just on your local host environment (such as XAMPP). For example in actual website deployment in a production server; it will be subjected to two stressing conditions:

a.) Number of connections to that application – these are the number of visitors to your website which are connected to that application. The higher the number of visitors to that application, the higher also the number of connections. This is a stressing condition because sometimes if your PHP web application in your website is poorly written, it will result to a very poor performance in actual deployment which can slowed down if there are a lot of users in your website.

b.) Number of concurrent users – these are the actual number of users that are using the application at exactly the same time. Of course in a very low traffic website, the concurrent users is almost zero because the probability that two users will exactly hit the application and do the same request is very small. This can be an issue with high traffic websites; it is because the number of concurrent users can slowed down the application and put a signficant load on the web server. Some web host even limits the number of concurrent users (typically those that are originating from a free web hosting scheme).

The good thing with Apachebench is that you measure the performance of a certain web application or website given a stress conditions. The stressing conditions required by Apache bench are two above. What is expected to happen is that a poorly written PHP web application will perform poorly under stressing conditions. This is why performance benchmarks of CMS, PHP frameworks, etc are using ab testing to evaluate the quality of the application.

How to Get Started with AB testing tool in Linux/Ubuntu:

Below are the steps :

1.) In Ubuntu, Apachebench can be installed using the Apache 2 utils. Go to Applications – Accessories – Terminal, at the command prompt type:

sudo apt-get install apache2-utils

2.) After installation, you are now ready to use Apachebench. Lets have an example. Supposing you will need to know how performs when there are 300 connections and 3 concurrent users. First, this is the syntax of ab:

ab -n [number of connections] -c [number of concurrent users] [url]

3.) Using the syntax above for ab test, below is the final command to type in the shell prompt:

ab -n 300 -c 3

4.) Below are the results, you should see in your terminal:

This is ApacheBench, Version 2.3 <$Revision: 655654 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd,
Licensed to The Apache Software Foundation,

Benchmarking (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Finished 300 requests

Server Software:        nginx
Server Hostname:
Server Port:            80

Document Path:          /
Document Length:        9172 bytes

Concurrency Level:      3
Time taken for tests:   72.917 seconds
Complete requests:      300
Failed requests:        296
   (Connect: 0, Receive: 0, Length: 296, Exceptions: 0)
Write errors:           0
Total transferred:      2789682 bytes
HTML transferred:       2743782 bytes
Requests per second:    4.11 [#/sec] (mean)
Time per request:       729.172 [ms] (mean)
Time per request:       243.057 [ms] (mean, across all concurrent requests)
Transfer rate:          37.36 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      214  225   6.8    224     253
Processing:   448  502 177.6    486    3481
Waiting:      221  252 175.9    237    3232
Total:        670  728 179.0    710    3722

Percentage of the requests served within a certain time (ms)
  50%    710
  66%    721
  75%    728
  80%    735
  90%    751
  95%    771
  98%    818
  99%    931
 100%   3722 (longest request)

Very important interpretation of results:

1.) It means it takes 3722ms for to serve longest request under a stressing conditions of 300 connections and 3 concurrent users. This is the longest response time.

2.) But on the “average” it will only take to respond within 728ms +- tolerance of 179 ms.

A more powerful and faster website can respond to faster times even with more stressing conditions. If you are using Windows, you can read this Apachebench tutorial using Windows OS.

Warning: Do not use Apachebench excessively to make enormous request to a web server that you do not own. This is a form of denial of service attack and can put you to jail:

Apache Landing Page

This code list the directories and files in a table.

<!DOCTYPE html>
   <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
   <title>Ze Master Server of The Universe</title>
     html,body {
         font-family: "Lucida Console", Courier, monospace;
         text-shadow:1px 1px 1px #cacaca;
         -webkit-text-shadow:1px 1px 1px #cacaca;
         -moz-text-shadow:1px 1px 1px #cacaca;
         padding: 2px 0 0 24px;
         cursor:url(hand.gif), progress;
         margin:0 auto;
         border:1px solid #EEE;
         padding:7px 0 5px 10px;
         font-family: Verdana, Arial, Helvetica, sans-serif;
     .head span{font-size:9px; letter-spacing:0;}
         padding:0 0 10px 10px;

     /*icons for file types (add more to suit your needs - icons by famfamfam.)*/

     a[href$=".jpg"] {background: url(image.gif) no-repeat left 50%;}
     a[href$=".gif"] {background: url(image.gif) no-repeat left 50%;}
     a[href$=".png"] {background: url(image.gif) no-repeat left 0%;}

     a[href$=".pdf"] {background: url(pdf.gif) no-repeat left 50%;}

     a[href$=".psd"] {background: url(psd.gif) no-repeat left 50%;}

     a[href$=".doc"] {background: url(doc.gif) no-repeat left 50%;}
     a[href$=".txt"] {background: url(doc.gif) no-repeat left 50%;}

     a[href$=".avi"] {background: url(video.gif) no-repeat left 50%;}
     a[href$=".m4a"] {background: url(video.gif) no-repeat left 50%;}
     a[href$=".mov"] {background: url(video.gif) no-repeat left 50%;}
     a[href$=".mp4"] {background: url(video.gif) no-repeat left 50%;}
     a[href$=".wmv"] {background: url(video.gif) no-repeat left 50%;}

     a[href$=".mp3"] {background: url(audio.gif) no-repeat left 50%;}
     a[href$=".wma"] {background: url(audio.gif) no-repeat left 50%;}
     a[href$=".aac"] {background: url(audio.gif) no-repeat left 50%;}

     /*web pages*/
     a[href$=".html"] {background: url(html.gif) no-repeat left 50%;}
     a[href$=".php"] {background: url(html.gif) no-repeat left 50%;}


   <div id="container">
         // opens this directory
         $myDirectory = opendir(".");

         // gets each entry
         while($entryName = readdir($myDirectory)) {
           $dirArray[] = $entryName;

         // finds extention of file
         function findexts ($filename)
           $filename = strtolower($filename) ;
           $exts = split("[/\\.]", $filename) ;
           $n = count($exts)-1;
           $exts = $exts[$n];
           return $exts;

         // closes directory

         //  counts elements in array
         $indexCount   = count($dirArray);

         // sorts files

         // print 'em
         print("<h1>Directory Contents</h1>");
         print("<table width='100%' cellspacing='10'>
                   <td class='head'>Directory/File</td>
                   <td class='head'>Type</td>
                   <td class='head'>Size <span>(bytes)</span></td></tr>\n");

         // loops through the array of files and print them all
         for($index=0; $index < $indexCount; $index++) {
               if (substr("$dirArray[$index]", 0, 1) != "."){ // don't list hidden files
               print("<tr><td><a href='$dirArray[$index]'>$dirArray[$index]</a></td>");


LAMP on Ubuntu 11.10

The Ubuntu development team has made it very easy to install and set up a web server. Open a terminal window and enter the following command.
sudo apt-get install lamp-server^

Please enter the command exactly as it’s shown above. The carat (^) is not a typo and the command will not work without it.

Command to install LAMP

If prompted, enter your password.

The package manager will now display a list of packages to be installed. Hit to confirm that you want to go ahead with the install.

Installing LAMP packages

Apt will now start downloading and installing the packages on your computer.

After a short wait, you will be prompted to set a password for MySQL’s administrative user. Enter a password at the prompt and make sure it’s something you will remember or make a note of it.

MySQL password

You will then be prompted to confirm your password.

Confirm MySQL password

Type in the same password and hit . The package manager will now continue downloading and installing packages. After a short wait the installation will complete.
Testing Apache

Now we’ll run a quick test to make sure that the Apache web server is working. Open a web browser and enter the address https://localhost/. You should see a page that says “It Works!”

Testing Apache installation
Testing php

Now that we’ve verified that Apache works, we need to verify that php is working properly. We’re going to create a file in the /var/www directory called testing.php. Enter the following command in the terminal to create the file.
echo “” | sudo tee /var/www/testing.php

Enter your password if prompted.

Now you’ll need to restart the Apache web server. Enter into the terminal:
sudo service apache2 restart

Now open your web browser and enter the following address: https://localhost/testing.php

You should see a web page that displays a bunch of information about your php and Apache environment.

Testing php
Configure MySQL

Since this is for a local development environment, the MySQL database needs to be bound to the localhost IP address. This should be by default. You can verify your localhost address with the following terminal command.
cat /etc/hosts | grep localhost

You should see output something like this: localhost
::1 ip6-localhost ip6-loopback

Now you need to verify that this address is the bind address MySQL’s my.cnf file. Use the following terminal command.
cat /etc/mysql/my.cnf | grep bind-address

You should see output like this.

bind-address =

If it’s not correct you’ll need to edit /etc/mysql/my.cnf as root to fix it.
Install phpMyAdmin

You now have a functioning LAMP installation. You don’t need to install phpMyAdmin, but it provides a much easier way to administer your MySQL databases if you’re not familiar with MySQL’s commands. You can install phpMyAdmin with:
sudo apt-get install libapache2-mod-auth-mysql phpmyadmin

Enter your password if prompted.

Installing phpMyAdmin

Again the package manger will show you the packages it’s about to install. Hit to move forward with the installation.

The package manager will now begin downloading and installing packages. After a short wait you will be prompted to choose the web server to configure for phpMyAdmin. Hit to mark apache2 with an asterisk (*) as it’s shown in the following picture (click on the image to see it in full size). Then hit .

Select apache2

The next screen will ask about some automatic database configuration with dbconfig-common. Hit to accept the default and move on.

Configure phpMyAdmin with dbconfig-common

Next you’ll be prompted for the MySQL administrator password. Enter the password that your created earlier.

Enter MySQL administrator password

Now you’ll be prompted for a MySQL application password. You can allow the system to generate a random password or choose your own.

Enter MySQL application password

If you choose your own password, you will be prompted to verify it at the next screen.

Verify MySQL application password

Your phpMyAdmin installation and configuration is now complete.
Testing phpMyAdmin

Open your web browser and enter the address https://localhost/phpmyadmin/.

You should see a page like this.

phpMyAdmin login screen

Now log in with the user name root and the password that you created earlier in the tutorial.

phpMyAdmin Home screen

Congratulations, you now have a working web development environment set up on Ubuntu 11.10. You can place the files for your website under /var/www. Note that this location is owned by the root user, so you’ll need to copy your files over as root for it to work. Otherwise, you can do some further Apache configuration so you can place the files for your website in a directory somewhere under your home directory.
Fixing some common problems
Fixing phpMyAdmin

One common error that some people make is that they forget to mark apache2 during the phpMyAdmin configuration. When this happens you’ll get a 404 Not Found error when trying to navigate to https://localhost/phpmyadmin/.

phpMyAdmin Not Found

If this happens, enter the following terminal command.
sudo dpkg-reconfigure phpmyadmin

You will be prompted about reinstalling the database. Accept the default of “No” and hit .

Don’t reinstall phpMyAdmin database

Make sure to then mark apache2 by having the cursor next to apache2 and then hitting to mark it with a *, then hit .

Reconfigure phpMyAdmin for Apache

You will then need to reload Apache.
sudo service apache2 reload

You should now be able to load https://localhost/phpmyadmin/. If you’re still seeing the 404 Not Found error, then you will need to clear your web browser cache and try again.

phpMyAdmin login screen
Fixing the Apache fully qualified domain name

During the above steps you may have seen an error message like this when reloading Apache.

apache2: Could not reliably determine the server’s fully qualified domain name,
using for ServerName

This doesn’t seem to cause any problems for me, but if you don’t like seeing that error, you can fix it with this command.
echo “ServerName localhost” | sudo tee /etc/apache2/conf.d/fqdn

Then reload Apache with
sudo service apache2 reload

Enjoy your new web development environment!