NTP Server and Client Configuration

NTP stands for Network Time Protocol, and it is an Internet protocol used to synchronize the clocks of computers to some time reference. NTP is an Internet standard protocol that is implemented via UDP over port 123. It is the best way to set your system clock correctly.

According to a Survey of the NTP Network, there were at least 175,000 hosts running NTP in the Internet. Source: http://alumni.media.mit.edu/~nelson/research/ntp-survey99/

Here is a step by step guide on how to configure NTP on your Ubuntu machine. Please read my previous post to better understand this guide for NTP Server and Client Configuration.

NTP Server Configuration

Step 1: Install NTP server on your machine.

sudo apt-get install ntp

Step 2: Configure NTP server. NTP’s default main configuration file is located at /etc/ntp.conf.
a: add a number of servers to the server list

server 0.asia.pool.ntp.org
server 1.asia.pool.ntp.org

b: restrict the server’s type of access

restrict otherntp.server.org mask 255.255.255.255 nomodify notrap noquery
restrict ntp.research.gov mask 255.255.255.255 nomodify notrap noquery

Servers are not allowed to modify the run-time configuration or query your own NTP server.

c: set the localhost to have full access without any restricting keywords

restrict 127.0.0.1

d: define the network where NTP synchronization requests are accecpted by the NTP server

restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

Step 3: Stop NTP.

/etc/init.d/ntp stop

Step 4: Run ntpdate command.

ntpdate 192.168.1.1

Step 5: Start NTP for the settings to take effect.

/etc/init.d/ntp restart

Step 6: Check if NTP is synchronized.

ntpq -p

Configured time servers are listed. For correct synchronization, the delay and offset values should be non-zero and the jitter value should be under 100.

NTP Client Configuration

Follow the same steps provided above and set your server configuration setting to your own server’s current ip address.
server configuration settings on ntp.conf

#server 192.168.1.1

Managing User Accounts (Files and Commands)

etc/passwd contains the user account information(for human or non-human users). Non-human users like sshd also owns files and run processes.

Format:
username:password:userid:groupid:GECOS:homedirectory:loginshell

e.g:

diane:x:1000:1000:Diane Palo,,,:/home/diane:/bin/bash
sshd:x:115:65534::/var/run/sshd:/usr/sbin/nologin

All added users will have a userid of greater than or equall to 1000.

To suspend an account, replace the login shell to bin/false or sbin/nologin to prevent the user from logging in to the machine. Setting the login shell to bin/false or sbin/nologin is used to create limited accounts.

/etc/shadow contains user password information.

Format:
username
:password
:days since Jan 1, 1970 that password was last changed
:days before password may be changed
:days after which password must be changed
:days before password is to expire that user is warned
:days after password expires that account is disabled
:days since Jan 1, 1970 that account is disabled
:a reserved field

e.g:

diane:$6$CnGqE0NA$iLrquxZUS6bqnAbffVNtS/BRy2CB/abthemvhyUHm9A5EK8YdZtj0fSAEhUg8B2YConm0hXCuJsaItAr6RU5R1:15165:0:99999:7:::

Password is encypted, a hash of the password.

Add ‘!’ to disable an account temporarily or sudo passwd -l username.
Remove ‘!’ to enable the account or sudo passwd -u username.
To change user password expiry information, use chage username.

Commands:
passwd – change password
syntax:
passwd password

pwconv – moves all user password information from /etc/
passwd to /etc/shadow
syntax:
pwconv

pwunconv – moves all password information from /etc/shadow to /etc/passwd then deletes /etc/shadow
syntax:
pwunconv

useradd – create an account
syntax:
adduser username

userdel – delete an account
syntax:
userdel username

usermod – modify an account
syntax:
usermod username

Other Commands:

finger – display user’s information.
syntax:
finger username

chfn – change user’s information.
syntax:
chfn username

List Installed Packages in Debian

List all currently installed packages.

dpgk --get-selections 

Find the location of a package

dpkg -L package

MAC OS X-Look for Ubuntu

To transform Linux’s appearance and layout into a Mac OS X environment, type the following commands on your terminal:

1. Donwload the file from the link of macbuntu project. (for Ubuntu 10.04 Lucid Lynx).

https://sourceforge.net/projects/macbuntu/files/macbuntu-10.04/v2.3/Macbuntu-10.04.tar.gz/ -o /tmp/mMacbuntu-10.04.tar.gz

2. Untar the downloaded file to th /tmp directory.

tar -xzvvf /tmp/Macbuntu-10.04.tar.gz -C /tmp

3. Go to the untarred file

cd /tmp/Macbuntu-10.04

4. Install

./install.sh

To uninstall:
1. Go to the Macbuntu directory

cd ~/.macbuntu/10.04-2.3/

2. Uninstall

./uninstall.sh

Enjoy your MAC OS X-like environment! 🙂

Speed Up Package Downloads and Updates with apt-fast

Use apt-fast instead of apt-get for faster download speed in downloading and updating packages in Ubuntu.

To use apt-fast:

1. Download the file apt-fast.sh from http://www.mattparnell.com/linux/apt-fast/.
2. Rename the file to apt-fast [mv apt-fast.sh apt-fast].
3. Move the file to /usr/bin [mv apt-fast /usr/bin].
4. Add execution permission to the file [chmod +x apt-fast].
5. Use apt-fast to download/upload packages.

apt-fast install package

apt-fast update

Faster downloading and updating time with apt-fast!

Firefox 5.0 in Ubuntu 10.04

Firefox is running on my Ubuntu OS but the latest version is not yet installed. To upgrade Firefox with the latest version, just enter these three simple commands on your terminal.

sudo add-apt-repository ppa:mozillateam/firefox-stable
sudo apt-get update firefox
sudo apt-get upgrade firefox

Or you may use the Ubuntu Software Center for upgrading Firefox. I prefer upgrading my application using the terminal since it requires fewer steps. Anyway, here are the steps if you wish to upgrade through a graphical interface.

Go to Ubuntu Software Center
Select Edit Menu > Software Sources...
Add [php]ppa:mozillateam/firefox-stable[/php] on Software Sources
Go to System > Administration
Click Update Manager, and then perform the update.

Congratulations! You now have the latest version of Mozilla Firefox.

Linux Ubuntu Desktop

The good news? It is now easier to use a Linux OS on your machine. Unlike before, it is just used by geeks working with command lines. Thanks to the power of user interfaces, thanks to GNOME. Well, I won’t discuss much of GNOME here. But as an overview, it is the reason why Linux is now a user-friendly OS. Linux desktop have its similarities and differences with Windows. Linux and Windows do have same functionality. Things you do with Windows, can be done with Linux as well. Applications on Windows do have have a corresponding application in Linux. The difference? One observation is the position of the minimize/maximize/close button, start menu button, and the task bar icons.

Another difference is: in Linux, you can move to another workspace but in Windows, you can’t. What a great feature, isn’t it? So helpful to those who open numerous applications. Additional great features are: Ubuntu Software Center and Network Tools.

With Ubuntu Software Center, application are categorized. This feature provides an efficient way of searching installers. With network tools, networking guys would really appreciate this one. You can do network-related stuff in one window.

I wont put much details about Linux Desktop. If you’re interested, just explore it and eventually you’ll get used to it and discover another great feature. Those three features are some of the great features i love with Linux. The main disadvantage of Linux is the availability of some software and drivers but there are always alternative to those unavailable installers.