Hello,

The last days I keep trying to configure my server. I know how to configure the network to this:

MODEM -> (eth0) Servidor (eth1) -> (LAN Port) Router (LAN Ports) -> Computers

This topology don`t work for me, because in this way I lost one WAN Port. So I thought in this topology:

MODEM -> (eth0) Servidor (eth1) -> (Porta WAN) Router (Portas LAN) -> Computadores

First of all configure your eth1 manyally as (edit /etc/network/interfaces):

auto eth1
iface eth1 inet static
address 192.168.100.254
netmask 255.255.255.0
network 192.168.100.0
broadcast 192.168.100.255

After this I add this iptables rules:

sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING –out-interface eth0 -j MASQUERADE
iptables -A FORWARD –in-interface eth0 -j ACCEPT

I need to setup the router manually:

IP Address : 192.168.100.1
Subnet Mask : 255.255.255.0
ISP Gateway Address : 192.168.100.254
Primary DNS Address : 200.247.141.11 (DNS)
Secondary DNS Address : 200.247.141.12 (DNS)

So up and running

Matheus

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Hello,

Today I will just recomment to you the post of Juliano Martins about how o install Ubuntu from pendrive.

UPDATE: In the last days I tried the tool from Ubuntu (USB Startup Disk Creaator) and it works!

Best Regards,
Matheus

Good night,

To install ssh server in Ubuntu use:

$ sudo apt-get install openssh-server

To let it safer edit /etc/ssh/sshd_config

$ sudo vi /etc/ssh/sshd_config

Than change the lines:

AllowUsers USER
AllowGroups GROUP_USER
PasswordAuthentication yes
MaxStartups 2:100:2
Port XXX # Change the port

What MaxStartups do? Specify the number of un authenticated connections in server. The syntax is start:percent:max. Example: 10:50:20. When it gets to 10 connections it will start with the percent. So every new connection will have 50% of chance to be automaticlly refused. When it gets to 20. It will denied ALL the new connections.

If you want, you can ask for a second password, if you type it wrong, it will close the connection:

Edit /home/user/.profile

echo Put your password
read senha
if [ $senha == "SOMETHING" ]
then
# CODES THAT ALREADY ARE AT .profile
else
exit
fi

With this you can do some tricks, to create a new RANDOM password every time somebody connect and send it to your e-mail. So you will need to put your normal password, than access your e-mail account, verify the new password and type it.

Best Regards,
Matheus

References:
Desabilitar Comando SU
Informação MaxStartups

Good Night,

This is a simple tip, how to execute some file in computer startup. (I used this tip to enable the port forward on startup)

Copy your file to /etc/init.d/ using “cp file /etc/init.d/file”

Edit /etc/rc.local (as root) and add the file that you want to execute. You must use the full path like /etc/init.d/file.sh for example.

The file must have execution permissions, do this using “chmod +x /etc/init.d/file.sh”

Matheus

PS: You must add the line before “exit 0″ in rc.local

Good afternoon,

If you want to forward ports to a virtualmachine in VirtualBox you should do this:

Create an interface “tap”

#sudo tunctl -u $USER

Set the tap address:

#sudo ip addr add 192.168.0.20/32 dev tap0
# sudo ip link set tap0 up

Enable Ip Forward

# sudo sysctl net.ipv4.ip_forward=1

Add route:

#sudo route add -host 192.168.0.150 dev tap0

Create nat:

# sudo iptables –flush
#sudo iptables -t nat –flush
#sudo iptables -t nat -A POSTROUTING –out-interface eth1 -j MASQUERADE
#sudo iptables -A FORWARD –in-interface eth1 -j ACCEPT

Redirecting port 3333 to 3389:

#iptables -t nat -A PREROUTING -i eth1 -p tcp -d 192.168.0.100 –dport 3333 -j DNAT –to 192.168.0.150:3389

eth1 – Ethernet connected to the router.
192.168.0.150 – IP of virtualmachine
192.168.0.20 – IP of tap
192.168.0.100 – IP of my real machine that receive the connections in 3333

After this configure manually your virtualmachine to:

IP: 192.168.0.150
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.0.100

I had problems with ‘–’ so here is a file with the commands: Forward ports to a virtualmachine.

Hope this is usefull,
Matheus

References:
IPtables Tutorial
IPTables Port Redirect
VirtualBox, com nat
VBoxManage Port Forward

Good night,

A few days ago I created a XML-RPC server to test some functions. What is XML-RPC? XML-RPC is a remote procedure call (RPC) protocol which uses XML to encode its calls and HTTP as a transport mechanism.(wikipedia) To start using XML-RPC in Java I used apache xml-rpc.

Example client and server XML-RPC.

Best Regards,
Matheus

Hello,

Today in class one of my teachers was using Windows 7 as your “main” operational system. He said “Windows 7 never crashed”. So i decided to try it too in VirtualBox.

You have to access Microsoft Windows 7 page. Download the version you want to use. You will have to fill a form and then you will receibe a mail confirmation. When you confirm it you will be able to access a page with the link location and your cd-key.

Open your Virtual box go to “New”, choose a name. Change the options to Windows, version Windows 7 (32/64). Create, set the memory size. Create a new Virtual HardDisk. (I used 15GB). Start it, choose the image file and start the installation.

(Installation is so easy, i will not comment it here.)

Matheus

PS: I know I haven’t published regularly in the last days, but I’m sick (flu) and I’m testing some stuff that take a lot of time like IPV6.

Hey,

Just a fast tip, if you want to have a ssh server more secure disable root access in “/etc/ssh/sshd_config”

Find the line starting with PermitRootLogin and set it to nojust like this:
PermitRootLogin no.

I already setup my ubuntu server, and have infos about ssh and other configurations. I’m translating the old articles to english first, so don’t get angry if I take a little time to post it. I hope in the next month the portuguese version and the english, start to run together

Bye,
Matheus

Good Night,

Here I will show you how to create your own url shortener.

First of all you need to create a table like this:

CREATE TABLE IF NOT EXISTS `urls` (
`uid` int(11) NOT NULL auto_increment,
`url` text default NULL,
`unique_chars` varchar(25) BINARY NOT NULL,
PRIMARY KEY (`uid`),
UNIQUE KEY `unique_chars` (`unique_chars`)
);

This code was taken from Abhise in this post “Create your own tinyurl with php and mySQL” that was my bigest reference, from it I took some functions and update other ones to be more efficient. For an example I changed the field to BINARY so it be CASE SENSITIVE (aaaa different from AAAA)

The Abhise says to create many files, I particularly, created one file with all functions where I add all the functions and just called the functions in the files.

Read more »

Hello,

A few weeks ago I had a test of Concurrent programming (INE5410), where I had to implement a RankSort in Pascal FC. In this problem we have a Vector that must be order by N process. After the test the professor send us an resolution that I will put here.

- RankSort implementation in Pascal FC.
- Pascal FC editor for windows

Best Regards,
Matheus