Category Archives: Linux

How to display PHP errors only in public_html directories

How to display PHP errors

I always use servers where PHP errors are not shown by default and I always forget how to enable error messages in development environments.

My situation

On a server I usually prefer Debian OS, but when I develop on the go I use laptops with Ubuntu.
In this case I’m running Ubuntu 14.04 LTS with Apache2 (v2.4.7) and libapache2-mod-php5 (v5.5.9).

I want PHP errorors displayed for projects in my public_html folder.

Solution 1 (only Apache conf files)

Create the file /etc/apache2/sites-enabled/800-public-html.conf with this content:

<Directory /home/*/public_html>
  AllowOverride Options
  php_admin_flag display_errors On

Solution 2 (using .htaccess)

Create the file /etc/apache2/sites-enabled/800-public-html.conf with this content:

<Directory /home/*/public_html>
  AllowOverride Options

Create the file /home/max/public_html/project1/.htaccess with this content:

php_admin_flag display_errors On


It’s easy and easily forgettable. Don’t forget to add

error_reporting(E_ALL | E_NOTICE);

in your .php files.

Restore an etc configuration file from the original maintainer version on Debian

There are events that can not be stopped, for example when you delete a file by mistake under /etc.

Debian provides an elegant way to restore files of the maintainer’s version without touching your existing configuration.

Practical scenario

Let’s say I’ve removed the file /etc/apache2/sites-available/000-default.conf, here’s the procedure to recover it:

  • find the deb package containing the file
    # dpkg -S /etc/apache2/sites-available/000-default.conf
  • reinstall the package with a specific option
    # apt-get install --reinstall -o Dpkg::Options::="--force-confmiss" apache2
    Reading package lists... Done
    Building dependency tree       
    Reading state information... Done
    0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 5 not upgraded.
    Need to get 86,7 kB of archives.
    After this operation, 0 B of additional disk space will be used.
    Get:1 saucy-updates/main apache2 amd64 2.4.6-2ubuntu2.1 [86,7 kB]
    Fetched 86,7 kB in 0s (264 kB/s)
    (Reading database ... 245864 files and directories currently installed.)
    Preparing to replace apache2 2.4.6-2ubuntu2.1 (using .../apache2_2.4.6-2ubuntu2.1_amd64.deb) ...
    Unpacking replacement apache2 ...
    Processing triggers for man-db ...
    Processing triggers for ufw ...
    Processing triggers for ureadahead ...
    ureadahead will be reprofiled on next reboot
    Setting up apache2 (2.4.6-2ubuntu2.1) ...
    Configuration file `/etc/apache2/sites-available/000-default.conf', does not exist on system.
    Installing new config file as you requested.
     * Restarting web server apache2

That’s all.

Practical scenario #2

There’s another interesting case when this procedure comes handy: if you changed a default etc file and you want to restore it. In that case you can simply delete it and use the same apt-get command:

# apt-get install --reinstall -o Dpkg::Options::="--force-confmiss" <package name>


Dockerfile: “no such file or directory” error using ADD

Testing docker is really interesting, but sometimes it’s difficult to understand what’s wrong with some configuration.

A problem I found recently dealed with the ADD directive used in the Dockerfile. I was trying to start some services with supervisor but I got this error during the image build process

Step 19 : ADD supervisord.conf /etc/supervisor/conf.d/
2014/02/10 00:40:55 build: supervisord.conf: no such file or directory

The file was right there, in the same path of the Dockerfile, but docker couldn’t find it.

After a good read of the official documentation I learned the conxept of “build context”. When you are building an image, the source directory from which you are operating is the build context, but when you are building passing the Dockerfile from the standard input, there’s no build context!

So this is ok

$ docker build -t mydebian .

and this can’t work

$ docker build -t mydebian - < Dockerfile