Me in IT UNIX/Linux consultancy

It's been one month (23 days) since I move to Amazons EC2, aka Amazon Cloud, aka AWS. Overall I am very pleased with the performance of my instance, which I use as a webserver. Also the extra volumes perform great. It's been up for 100% in Januari 2009.

Here are some numbers so you can get an estimate of what Amazon EC2 cost:

$0.11 per Small Instance (m1.small) instance-hour (or partial hour)	537 Hrs	$59.07
$0.100 per GB Internet Data Transfer - all data transfer into Amazon EC2	22.554 GB	$2.26
$0.170 per GB Internet Data Transfer - first 10 TB / month data transfer out of Amazon EC2	32.379 GB	$5.50
$0.010 per GB Regional Data Transfer - in/out between Availability Zones or when using public IP or Elastic IP addresses	0.023 GB	$0.01
$0.12 per GB-month of provisioned storage	23.073 Count	$2.77
$0.11 per 1 million I/O requests	4,398,873 Count	$0.48
Total		$70.09

Overall I'd recommend Amazon EC2, but it's a little more expensive than an average Private Hosting plan, but this setup is more scalable.

As a freelancer in Dutch IT, you will almost always use a contracting company. This company makes an initial contact with the end-customer and receives and pays your invoices.

When you are in contact with a new contracting company, you can check IT Bemiddelaars to see what a company has done before, compare rates and cost.

When you would like to review an "IT bemiddelaar", please go to IT Bemiddelaars to enter the information you'd like to share.

Besides the extensive OpenVPN documentation I couldn't really find a step by step guide on how to setup an OpenVPN server and client.

I want to be able to connect my Fedora Core 10 laptop to the home-network via a Fedora Core 10 server.

Overview of the network setup

The server is 192.168.0.1, running Fedora Core 10 with openvpn 2.1. Newer versions are likely to work as well.
The laptop has a dynamic IP address.

Setting up the server

Please read the OpenVPN documentation if you run into troubles.

First setup the Certificate Authority keys.

Now setup the Server key and the Diffie Hellman key.

And build the client keys, each client needs its own key, with a unique Common Name. The IP address assigned to the client is related to the Common Name, so if you use non-unique Common Names, you will have conflicting IP addresses.

Start the server by issuing:

Setting up the client

Move the ca.cert, client1.crt and client1.key to the client, in /etc/openvpn/keys and copy the configuration. You will need to modify the client.conf a little bit.

Start the client:

Checking if it worked

On both server and client issue ifconfig tun0 to see what IP-address is assigned to the entry of the tunnel. From the either end of the tunnel you should be able to ping the other end. Also tcpdump -n -i tun0 should work.

Hope this works for you as well, check out /var/log/messages for information. /etc/init.d/openvpn status dump a status of all connected clients to /var/log/messages.

It's very difficult to get grip on the estimates price of a "simple" LAMP server. Here are some numbers to help you get an accurate estimate of a LAMP server.

The setup

• One small Linux (Fedora) instance in Europe.
• One 30 Gb volume in Europe.
• Two 1 Gb volumes in Europe.
• Apache, Mysql on the same machine and PHP.
• Average daily visitors: 8000.

The price and numbers

• 730 small instance hours = $ 80.30
• 32 Gb of provisioned storage = $ 3.84
• 95 Gb traffic in = $ 9.50
• 27 Gb traffic out = $ 4.59
• 5 million IO requests = $ 0.55
• TOTAL $ 98.78 (Without tax)

So as a conclusion: One average webserver costs around $ 120,- (with tax) per month to run on the EC2. There are cheaper solutions to host your website(s), but Amazon EC2 provides the option to add a machine in a couple of minutes or even automated. This flexibility is not found in many other products.

While experimenting with Amazons interpretation of cloud computing, here is what I did to create persistent storage, create an instance and attach the storage to the instance.

Install and configure the local tools.

Go to Amazons developer section and download, unpack and install the files. Now edit ~/.bashrc (or any other file that is executed at login) and add this:

As you can see, I have the tools installed in ~/.ec2, the JAVA_HOME is set for a Mac OS X machine and I use the European Amazon infrastructure. Get a list of these regions with ec2-describe-regions.

Create a keypair.

Check out the wonderful section on Paul Stamatiou's website at "Getting Started". It describes how to create and use the keys.

Open ports 22 and 80.

You will have to authorize access from the internet to port 22 and 80, or any other. Here is how it's done:

default refers to all machines unless specified differently.
The option -p refers to a port number.

Create an instance.

An instance can be seen as an individual machine. It's virtual, but who cares about that? I use the image "ami-2a0f275e", but see other images can be used as well. Use ec2-describe-images -o amazon to get a list of available images owned (-o) by amazon.

The option -z specifies an "availability zone". Get a list of these zones with ec2-describe-availability-zones.
The option -k specifies what key to use. If you don't use this option, you will not be able to login using SSH.

Create a volume.

To allocate some space on the S3 infrastructure of Amazon, use this command:

The option -s 1 specifies that the size is 1 Gib.
The option -z is used to determine the availability zone, it needs to match the instance's zone.

Attach the volume to the instance.

When the volume is created; assign it to an instance with this command:

This only makes the device available, you will have to partition, format and mount it to use it.
The argument vol-38a24751 describes the volume to attach. Use ec2-describe-volumes to get a list of available volumes.
The option -i specifies the instance. Use ec2-describe-instances to get a list of available instances.
The option -d specifies the name under which Linux will recognize the volume. Login to you machine, type dmesg to see if attaching has worked. This is the ouput I got:

Logging into your instance

Login to your machine using SSH:

The option -i specifies the identity to use.
The argument MACHINE needs to be replaces with the public DNS name of you instance. Get a list of the named using describe-instances.
If you like to type less; add this to your ~/.ssh/config file:

From the moment on that you have added this configuration, you can simply login to your instance without any options, just the DNS name of the instance.

Formatting and mounting the volume.

Now that you are ready, login and type:

Mount the volume (once) by issuing:

There is 924 Megabytes (Mb) available. so you'll lose some 80 Mb's for the filesystem.

Setting a static IP.

You can continue to use the instance with this "static" IP, but to associate one IP with this instance, follow these steps. First register an IP:

You will see the IP printed on your screen.

Now link the IP with an instance.

Conclusion.

The Amazon elastic compute cloud and S3 facilities work great, I'm not sure about the availability of EC2, not about S3, but Amazon states that S3 should be more "secure" then storing stuff in the local storage of the instance.

So you like bash, just like me. There are times though where you'd need to work on a machine where there is no bash, but ksh(3). Here is a list of commands and keys to help you:

Go back in history

Hit escape a few times, now hit "k" and "j" to move back and forward into the history.
Edit the command with the letters "h" and "l".

Complete commands

Type a part of your command, hit escape a few times, now hit "\" to complete the command.
You can't display what your options are, (in bash just tab a few times)

Get a decent prompt

Either run this command once, or add it to your ~/.profile:

One major problem; the PWD variable does not change when changing directories!

Have you ever heard of (or used) a group password in Linux? For me this strange concept was new, but here's what you can use it for.

A group password in Linux allows a user to temporarily (in a subshell) gain extra permissions of a group, after successfully entering the group password.

To set a group password use gpasswd:

To gain those extra permissions you can use newgrp:

Some of the disadvantages are:

1. Sharing a password is not good; a password should be personal.
2. You can also solve this by adding the user to a secondary group.
3. Another way to solve it is to use sudo.
4. Usage of the group password is not accountable.

The User Mask (umask) can be managed with the command umask. A umask is the reverse value of the octal permission set that files and directories are created with.

So, a umask of 0777 creates files with an octal permission value of 0000; no permissions to read, write or execute.

But; there is a strange thing about the umask; it never allows to make files executable. Here is a demonstration of this "flaw"/"security feature".

I would have expected 750, instead 640 is produced. This is default security behaviour of UNIX/Linux.

Network Address Translation is a technique to masquerade IP addresses on your internal LAN to the outside world. In other words; the outside world will not be able to look into your network.

This technique is easy to setup and maintain, saves IP addresses and is likely more secure that pure routing. To set it up, you require:

1. A Linux machine, for this example Fedora Core 9
2. Two network cards, eth0 attached to you LAN, eth1 connected to the internet.
3. A little bit of Linux/UNIX knowledge
4. 30 minutes or so

Enable IP forwarding

To be able to use IP forwarding, you must tell the kernel that it's okay to forward traffic from one network card to another. This setting is found in /etc/sysctl.conf. Set net.ipv4.ip_forward to 1.
To do this, execute:

The first command enables IP forwarding now, a reboot would undo this setting. To enable this setting for every reboot, also execute that second line.

Enable the firewall (IPtables)

Make sure the service IPtables is running now and is started at bootup:

Configure the firewall (IPtables)

Now that the kernel knows it's allowed to forward traffic from one NIC to another, configure the firewall. The firewall is the intelligent part of setting up NAT, IPtables actually 'does the work'. Here are the commands to set it up:

Safe the firewall rules

You have only configured the firewall for now, a reboot would undo all settings. Run this command once you are happy with the setup:

Reboot to test the setup. Your LAN client will have to set the default route to the IP address of the NAT machine's LAN NIC.

There are a few ways to start (and stop) daemons at specific runlevels. For Fedora you could use modify how Apache (httpd) is started:

chkconfig --level 4 httpd on

This is a simple command line tool to tell the the startup facility to enable (on) the Apache (httpd) daemon at runlevel 4 (--level 4). Works great and fast, but the script httpd must have some parameters in the file to let chkconfig know what to do with it:

The lines chkconfig and description are mandatory. In this example, the chkconfig line tells the startup facility to start in runlevel 4, with a "priority" of 85. This priority can be seen with ls /etc/rc4.d. The numbers of the startup script represent the order of how they are started.

ln -s /etc/init.d/httpd /etc/rc4.d/S85httpd

A much simpler, more simplistic method to start Apache. This command symbolically links /etc/rc4.d/S85httpd to the startup script of Apache. Don't forget to also stop the daemons with this set of links:

ntsysv

A text-based graphical menu to enable or disable services.

serviceconf and system-config-services

A graphical interface to enable or disable services.