Apache2 Notes

Enabling a module

On seeing this error:

.htaccess: Invalid command 'RewriteEngine'

This indicates that rewrite module is not enabled. In Apache 2, both module and sites are handled in the separated folders under /etc/apache2:

mods-available/
mods-enabled/
sites-available/
sites-enabled/

In the *-available folders are the configurations to be used, for instance, here we need to enable rewrite module, we just type

sudo a2enmod rewrite

You see that rewrite.load is in the folder mods-available with the content:

LoadModule rewrite_module /usr/lib/apache2/modules/mod_rewrite.so

You will be notified to restart/reload the Apache service. Do it.

Enabling a website

We write the configurations as foo.com in sites/available:

<VirtualHost 127.0.0.3:80>
        ServerAdmin webmaster@example.com
        ServerName  localhost
        ServerAlias foo.com

        # Indexes + Directory Root.
        DirectoryIndex index.php
        DocumentRoot /var/www/foo


        # Logfiles
        ErrorLog  /var/www/foo/logs/error.log
        CustomLog /var/www/foo/logs/access.log combined
</VirtualHost>

Make sure there is a logs folder

cd /var/www/foo
mkdir logs

And then enable the website

sudo a2ensite foo.com 

Just to notice how to disable the website:

sudo a2dissite foo.com

Most importantly, enact the changes.

sudo service apache2 restart

Troubleshooting: Does PHP have write permission to a folder?

This article only talks about PHP installed alongside Apache under Linux (see here). Since PHP is run through libapache2-mod-php5. it inherits the permissions from Apache. So let's take a look about Apache. By default, it uses www-data user, to check this,

ps -u www-data

If it is so, you might get something similar:

PID TTY          TIME CMD
 1276 ?        00:00:00 php5-fpm
 1277 ?        00:00:00 php5-fpm
 1278 ?        00:00:00 php5-fpm
 1279 ?        00:00:00 php5-fpm
14934 ?        00:00:00 apache2
14935 ?        00:00:00 apache2
14936 ?        00:00:00 apache2
...

Now check user info and its group of www-data

cat /etc/passwd | grep www-data

The following shows up on my machine which says it doesn't belong to the root group or my administrator group.

www-data:x:33:33:www-data:/var/www:/bin/sh

We list the file permissions of the folder img/ to see apache's right:

ls -l | grep img

All right! Since Apache is in other group here, it doesn't have 'w' permission.

drwxrwxr-x 2 admin admin 4096 Nov 12 19:26 img

Then let's give him the permission. Notice that it is dangerous to do this, since in this way every user on the computer will have rights on this folder. Normally, we let the owner of the folder be Apache, and others can only read.

chmod o+w img

References

• Show All Running Processes in Linux
• Understanding /etc/passwd File Format

MS Windows Terminology Italian - English

La Terminologia principale del MS Windows in correspondenza fra italiano e inglese. The correspondence of MS Windows terminology between Italian and English.

account utente	User account
aggiornamento	update
arresta il sistema	shut down
attendere	wait
attivazione o disattivazione	activation or disactivation
avviare	start
barre degli strumenti	Tool bar
caricamento	loading
cerca	search
collegamenti	shortcuts
connessioni di rete	Network connection
Disinstalla o modifica programma	Uninstall or modify programs
disinstalla	uninstall
eseguire	execute
gestione attività	Task manager
Gestione dispositivi	Device Manager
ibernazione	hibernate
Immagini	Pictures
impostazioni	configuration
indrizzi	address
manutenzione	maintainance
Modalità provvisoria	Safe Mode
mostra desktop	show desktop
nuova	new
Pannello di controllo	Control Panel
proprietà	property
riavvia il sistema	restart
risoluzione problemi	Troubleshooting
Sistema e sicurezza	System and Security
souni	sound
stampante	printer
strumento	tool

To sort a random file by alphabet,

sort -gk 2 temp