Getting Started With Azure Linux VMs
Written by Mike James   
Thursday, 17 April 2014
Article Index
Getting Started With Azure Linux VMs
Setting up the VM
Permissions

Permissions

There is a problem that you are going to encounter over and over again when working with your new virtual machine - permissions. 

Linux/Unix permissions are a problem for a development system because they generally stop you from writing files and creating directories. 

My advice is that anytime something "strange" happens is to suspect that the file that you think you have just written hasn't been written or modified as you suppose. Don't believe the evidence of your eyes because many times FileZilla will not report a problem in writing a file - or will do it so quickly you don't notice. 

What is worse is that FileZilla will allow you to change permissions on files - but in most cases it wont actually succeed in changing them as you don't have permission to change them.

To successfully cope with permissions you have to use the command line as root, i.e. use sudo in an Ubuntu system.

To make sense of permissions a quick course for the beginner is needed.

Linux/Unix recognizes three types of user - the owner, the group and the public i.e. rest of the world and each can have read, write or execute permission on a given object. 

In general the owner has the highest permission and can usually do anything to the object. The group has next lowest and public the lowest. 

Every user can be a member of multiple groups but only one group is the users default group.

When a user creates a file they are the owner and the object can assign access rights to the owners default group. 

This system works well for a production system but less well for a development system. 

Take for example the document root /var/www.  This has to be accessible to Apache but only with read permission. The Apache process runs as user www-data and when your machine is first set up this user owns all of the folders and files from /var/www down. This means that you can ftp new files and folders. 

How to solve this problem?

There are a number of opinions but mostly based on what you should do in a production system. For a development system arguably the best solution is to change the ownership of all of the files and folders in the document root to the developer and make the developer's default group www-data or something with a more appropriate name.

The idea is that the owner and the group has all permissions needed to access and change the files and the rest of the world has minimum permissions. In a production system you can keep the same setup but the group would only have read access and its only member would be the Apache server. 

The first thing to do is to change the user to have www-data as their default group:

sudo usermod -g www-data azureuser

Next you need to change the owner and group of all of the files to azureuser and www-data:

sudo chown -R azureuser:www-data /var/www

the -R means perform the action recursivly on all files and folders. 

To check the ownership and group use:

sudo ls -l /var/www

or just look at the Owner/Group column in FileZilla. 

Finally you can set the privileges on all folders and files to read/write/execute for owner and group and to nothing for public:

sudo chmod -R 770 /var/www 

Following this you and any member of the www-data group should be able to work with the files via FTP or the command line. 

One recurring problem is that when you copy files from other locations the owner and group will be set to the user logged into to the FTP server and their default group. The permissions will also not be changed to 770 and so you might have to execute the chown and chmod commands on a regular basis.

There are ways around this but it would take us beyond this simple setup.

Finally notice that this isn't a good way to setup a production server as the www-data group has too many members and too many privileges to be secure. Also notice that in a production server permissions for folders and files should be different - look it up on the web.

Some Extras

Now you have a basic LAMP server what you do next depends on your preferences. 

The biggest problem that most Windows users will have is getting back in touch with the command line. There are somethings that can help:

  • Use PuTTY and copy and paste as much as possible.
  • To edit files the simplest thing to do is setup a local editor, my favourite is Notepad+ and then use FileZilla's remote edit facility to automatically download any file you want to edit into Notepad+.  When you have finished editing the file is automatically uploaded to the server. 
  • If you want GUI help in managing MySQL install phpmyadmin. As long as you are using the latest LTS Ubuntu you can do it using

sudo apt-get install phpmyadmin

all you have to do is select apache2 as the web server and supply a logon password for MySQL. To add phpmyadmin to the configuration files use:

sudo ln -s /etc/phpmyadmin/apache.conf
         /etc/apache2/conf.d/phpmyadmin.conf

and restart Apache

 sudo /etc/init.d/apache2 reload

 You can then access it using; 

 http://<hostname>/phpmyadmin

 

 If you want a more general GUI admin panel then try Webmin which is like cpanel but open source. To install it use:

sudo apt-get install perl libnet-ssleay-perl openssl libauthen-pam-perl libpam-runtime libio-pty-perl apt-show-versions python

some of these packages will already be installed. Next download the package:

sudo wget http://prdownloads.sourceforge.net/
      webadmin/webmin_1.580_all.deb

and finally install the package using

sudo dpkg -i webmin_1.580_all.deb

You also need to add an endpoint to port 10000 using the Azure manager so that webmin can be reached. 

endpoints

 

You also need to setup root with a password as webmin doesn't logon using SSH. 

sudo passwd 

After this you can run webmin using 

https://<hostname>:10000

and login root and whatever password you specified. 

From here you can setup other users and groups and generally work with the system without the command line.

You can also spend a lot of time setting up additional modules - but that's another story.

 

webmin

 

There is a lot more to learn if you want to administer a production server, but from the point of view of development this is more or less all you need to know. Your next step is to set up a development system like Netbeans or Visual Studio for the PHP website you are working on - lookout for a future article.

winazurenew

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Last Updated ( Thursday, 17 April 2014 )
 
 

   
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