Dropbox LAN sync - Save bandwidth and time with local dropbox LAN sync

If you are working in organization which uses Dropbox at the daily bases, you might came across with bandwidth issue especially when syncing large file across different computers. At normal the file should be uploaded to Dropbox servers and then downloaded to each individual computers where the file is shared and this is considerable large use of bandwidth and takes time especially if the file is large enough, but with Dropbox LAN syncing feature bandwidth can be saved and syncing time can be minimized.

What is Dropbox LAN sync?

Dropbox LAN Sync is a feature that allows you to download files from other computers on your network, saving time and bandwidth compared to downloading them from Dropbox servers.

The LAN Sync feature can speed up the syncing of files that exist on your local area network (shared folders and computers connected to the network). It allows Dropbox to check for new versions of a file on your network without having to download the copy of the latter from Dropbox servers.

What is Dropbox LAN sync prerequisites?

 If you want to force a LAN Sync, you’ll need two computers on the network with either the same account or a shared folder in common. Add a file to one of the computers, and the other computer should attempt a LAN Sync. The computers should be in the same LAN.

How to configure and enable LAN sync?

a. Install the Dropbox client on your PC: www.dropbox.com.

b. Allow Dropbox.exe in your firewall's settings: The LAN Sync feature requires access to port 17500 (TCP). Go to the Control Panel > Firewall > Allow app or feature through Windows Firewall.

c. Click on the Dropbox tray icon > Preferences. Go to the Bandwidth tab and tick the Enable LAN sync checkbox: Click on Apply > OK.


Enjoy!

How to enable remote desktop in Window Server 2012 R2 Core

Server Core is a minimal server installation option for Windows Server that provides a low-maintenance server environment with limited functionality.After installing window server core there greater possibility you won't have direct access to server so remote desktop is the best option for you, follow the below steps to enable remote desktop on window server core.

a. Login to the server
After login below is the screen your going to see,

Use the seen command line interface to enable remote desktop.

b. Migrate to system32 directory

cd \Windows\system32

c. Run the script below found in system directory which will show you the current state of remote desktop

cscript scregedit.wsf /AR /v

If it returns 1, that means the remote desktop is not enabled you need to enable it by running the following command

cscript scregedit.wsf /AR 0

As seen below:

d.  Check if remote desktop is enabled on firewall, by running the following command.

Get-NetFirewallRule -DisplayGroup "Remote Desktop" | format-table Name,enabled -autosize

If it return false, enable it by running the following

Enable-NetFirewallRule -DisplayGroup "Remote Desktop"

As seen below:

Now you're good you can manage your server any ware by using remote desktop client.
Don't forget to allow tcp/udp port 3389 on the router via port forwarding when the server is inside local area network.

CSF firewall installation and configuration for VOIP/PBX systems-Part 2

After installation of csf firewall and webmin done on part 1 of this document, part 2 will concentrate on only configuration of the firewall, configuration to be done is described in steps below.

a. Allowing IP/IP blocks with fully access to the server.
You may start the configuration by adding you own block which should have fully access to pbx/voip system,fully access means the ip's should have fully access to all ports on the server these IP's should be your private LAN ip or ISP ip's if your configuring service providers voip/pbx system, to do so logon to your system via https://serverip:1000, then go to System > ConfigServer Security & Firewall, then csf - ConfigServer Firewall section, add your ip/ip blocks to Quick Allow and Quick Ignore,as seen on example below:

Don't forget to click on Quick Allow and Quick Ignore to save it to configuration file.

You should also add you Voip provider IP, if your system is connecting to online voip provider, otherwise you might experience issue when calls are routed to voip provider.

b. Allowing specific ports for IP/IP blocks without fully access.
Now go Firewall Configuration, to add ports which should be accessible for anyone without fully access to the server, if your voip system is accessible from the Internet, these are ports will be seen directly from the Internet.
You may allow as many ports as you can  for ports going out, but you should restrict ports which are coming to your server as minimum as you can, as far as my research below ports working fine for PBX/VOIP systems,

   i. Incoming
Only allow voip/pbx pors 5060:5061 and 10001:20000 which are used as media ports for some pbx systems, so the setup may look as below.
       a. TCP
           5060:5061

         b. UDP
           5060:5061,10001:20000

   ii. Outgoing
As i said you may allow as outgoing ports as you can, no problem on this.

       a. TCP
           20,21,22,25,53,80,110,113,443
       b. UDP
           20,21,53,113,123,1000:65000

So the setting will look as below,

c. Blocking ping from outside
You may also need to block ping from outside as means of security, to do search for Allow incoming PING and change it from ON(1) to OFF(0).

d. Enabling the firewall
When all configuration is done, you should enable the firewall for it to be operation on your server, go back to the beginning of configuration file and look for TESTING part and turn it off, as seen below:

e. Testing the firewall
After enabling the configuration you should now test the firewall to make sure it works as intended, below are hints for testing.

-Test if all pbx users are able to call via the pbx, also monitor if they can hear the voice with required quality.
-Test if the users coming from restricted IP are able to access the admin interface of PBX/VOIP, i mean any traffic going to port 80/443, they should not as the access to only be available to allowed IP's.

There a lot of settings which can be done on CSF firewall, but above is minimum which can be used to lock down your VOIP/PBX systems,drop down comments if you face any problem implementing the settings.

Restricting specific users from sending email to external domains in Postfix

Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail, intended as an alternative to Sendmail MTA.

When configuring mail server especially for small companies there sometime a requirement to restrict some of the users from sending email to the Internet, and allowing them to send email only to local domain or some domains.

This howto is going to show you how to achieve that extra functionality, this howto is assuming you have working mail server already where by the users are able to send and receive emails.Below are steps,

a. Create a file to catch specific email address which should be restricted.

i. Change to root and open the main Postfix configuration file.

 ~$ sudo su -
 ~# vim /etc/postfix/main.cf

ii. Add rule that will catch limited addresses.

The rule should be added as the first line in smtpd_sender_restrictions as below.

smtpd_sender_restrictions =
check_sender_access hash:/etc/postfix/restricted_senders,

as below:

If you put the rule below any permit rule there possibly it won't work as required.

b. Create specific rule and add the address which should be restricted, am using jarasyola.co.tz domain for the sake of demonstration only, you're going to use you're actual domain in real implementation.

vim /etc/postfix/restricted_senders

Add the email address which should be restricted on above created file and save;

james@jarasyola.co.tz  local_only
vanessa@jarasyola.co.tz local_only

as below

c.i.The rule above says to route restricted emails to a ruleset called "local_only". You need to define it, before you can add rules to it. Open main.conf file and add local_only ruleset as restriction class.

smtpd_restriction_classes = local_only

ii. Then create the restriction class "local_only" and add rules. They are executed top to bottom - first match wins:

local_only=
check_recipient_access hash:/etc/postfix/local_domains,
reject

The two lines should look as below on postfix main.conf configuration file.

d. Lastly, define the local domains where restricted users should be allowed to send, here i allow my local domain only.

Create a file

vim /etc/postfix/local_domains

add the domain(s)

jarasyola.co.tz   OK

If the recipient domain is not in /etc/postfix/local_domains Postfix will look for the next rule.In "local_only" I wrote "reject".This is a static action, which always is true if Postfix tests it. It gives you what you want. Either the recipient domain is on /etc/postfix/local_domains or the request action (send a message) will be rejected.

Drop a comment if you face any difficult in implementing the setup, tuonane kwenye post nyingine.

CSF firewall installation and configuration for VOIP/PBX systems-Part 1

During installation of any PBX/VOIP systems, security is one of the first thing you should consider in mind as compromising the system may bring greater loss especially interms of Money. There are different ways of securing voip/pbx systems but this how to is going to explain how to lock it down completely by blocking all standard ports not accessible from the Internet and being only accessible via the specified subnet while allowing only specified ports to allow users being able to call and receive the calls.
This howto's is divided into two main parts, part 1 (involves firewall installation) and part 2 will concentrate on configuration of your firewall to meet your needs,below are steps.

a. Webmin installation
b. Csf Installation
c. Firewall configuration

a. Webmin Installation
Webmin is a web-based graphical tool for unix . It is used to manage services like User management, Disk managemet, Network, Iptables ( Firewall ), Cron, Apache, DNS, File sharing and much more.Webmin is a web hosting control panel like cpanel which provides easy to use interface for managing Unix like systems.

i. Install required packages first.

# yum -y install perl perl-Net-SSLeay openssl perl-IO-Tty

ii. Install Webmin.

Make sure to check for the latest version here (http://www.webmin.com/download.html). As the time of writting of this document the latest version is 1.791.

# yum -y install http://prdownloads.sourceforge.net/webadmin/webmin-1.791-1.noarch.rpm

The installation will be done automatically to the directory /usr/libexec/webmin, the administration username set to root and the password to your current root password. You should now be able to login to Webmin at the URL http://localhost:10000/. Or if accessing it remotely, replace localhost with your system's IP address.

More tweaks:
-Starting and restarting the service use:

# /etc/init.d/webmin start
# /etc/init.d/webmin stop
# /etc/init.d/webmin restart
# /etc/init.d/webmin status

-Changing webmin root password

In order to change webmin root account password use following command. ( Note: It will not change your systems root password )

-Change webmin default port
If you do not want to run webmin with default port, use below steps to change the default port.

Login Webmin as root >> Webmin >> Webmin Configuration >> Ports and Addresses… you can change port there.


b. Csf Installation

CSF(Config Server Firewall) is generally considered a more advanced firewall as there are more configuration options compared to other firewalls, while still being simple enough to install and configure that even novice administrators can use it.An alternative firewall to CSF is the Advanced Policy Firewall or APF.
Installing CSF should be as simple as downloading the source file to your server and installing it, follow the following steps to install it.

i. Migrate to src directory and remove any existed csf file.

# cd /usr/src
# rm -fv csf.tgz

ii. Download the firewall and extract the downloaded file

# wget https://download.configserver.com/csf.tgz
# tar -xzf csf.tgz

iii. Change to csf directory and run installation script

# cd csf
# sh install.sh

iv.Test whether you have the required iptables modules:

# perl /usr/local/csf/bin/csftest.pl

Don't worry if you cannot run all the features, so long as the script doesn't
report any FATAL errors

v. Remove old CSF/APF firewalls

You should not run any other iptables firewall configuration script. For
example, if you previously used APF+BFD you can remove the combination (which
you will need to do if you have them installed otherwise they will conflict):

# sh /usr/local/csf/bin/remove_apf_bfd.sh

vi. Integrating CSF with webmin

Inorder to manage csf firewall on web browser via webmin you're required to Integrate it to webmin.
Install the csf webmin module in:
  Webmin > Webmin Configuration > Webmin Modules >
  From local file > /usr/local/csf/csfwebmin.tgz > Install Module

To access CSF configuration file via Webmin go to System System > Security & Firewall

vii. Uninstallation CSF firewall

Removing csf and lfd is even more simple:

# cd /etc/csf
# sh uninstall.sh

viii. Removing Warning

In case you get this warning below:

*WARNING* URLGET set to use LWP but perl module is not installed, reverting to HTTP::Tiny

When accessing CSF firewall via Webmin, install perl module using command below.

# yum install perl-libwww-perl

That's it, check out part 2 for voip firewall configuration.