Enable Network Printer Sharing with Ubuntu Linux computers

Having a shared printer within a computer network is a nice thing to have. Since all computers within the network can access a remote printer to print documents. Maintenance cost is much more cheaper and easier since you only need to service only a single printer within a network.

Here’s how to enable Printer sharing with Ubuntu (or other Linux based computers) through GNOME :

At the computer with the printer

Administer Printers Ubuntu
  • First at the Desktop, go to System->Administration->Printing. A dialog will appear
  • Go to Server Settings, and check the “Share published printers connected to this system” checkbox

    Administer Printers Ubuntu

  • You may, optionally select “Allow users to cancel any job”
  • Click Apply, and close the dialog

At the client computer(s)

Network Printer Sharing Ubuntu, using Samba

  • From the Desktop, go to System->Administration->Printing. A dialog will appear
  • Check “Show shared printers from other systems” checkbox. Click Apply
  • Repeat the first step, this time click “Refresh Printer Queues” button. You shall see the list of shared printer from the server computer
  • Repeat this on other computers on the network to share the printer

That is all to it! Now you can print documents across your computer network.

How to Synchronize Current Time in Ubuntu

As some of you might aware, the time kept by computers (or other timepieces such as clocks) are not accurate as there are various factor that causes time drift. Quartz inaccuracy, temperature, quality of the equipment, power from battery, mechanical wear and tear and so on.

These minor drift while might not seems to be significant, it will give you inaccurate measure of time. This might affect your other productivity work as the time kept by your computer is not accurate to the last second. Plus, certain application such as Stellarium and GPredict depends heavily on the time kept on your computer to give accurate result.

How to get accurate time in Ubuntu
You can ensure your computer gets the most accurate time by synchronizing it with an NTP server .

To do this you need to right click the Tray Clock in Ubuntu, and selects “Adjust Date & Time”.

Adjust Date and Time

A dialog will appear, press “Unlock” and enter your Administrator password to enable the menus.

Adjust Date and Time

Answer “yes” to install NTP packages. If your computer is connected to the internet it will be automatically synchronized with an NTP server.

Bonus :You can select the nearest NTP server to your place for faster synchronization, as shown on the picture. The nearest NTP server to Malaysia is maintained by SIRIM – mst.sirim.my.

NTP Time Servers in Ubuntu

Synchronize Time using command-line
Alternatively you can synchronize time by using ntpdate command-line tool, which is covered previously in this blog.

Linux Kernel Hacking Lessons from LinuxChix

Those who are interested in understanding the Linux Kernel, and wants to be a Linux Kernel Developer might find this website interesting as a stating point, the LinuxChix Kernel Hacking Lessons.

Structured in an easy to follow lessons, the whole online course designed to make you familiar with the kernel development tools, linux system calls and the overview of the kernel source code structure. The course comes in 10 lessons which you may find it interesting as it offers simplified explanation and practical examples :

  1. Lesson #0: Check for Materials
  2. Lesson #1: Get the Kernel Source
  3. Lesson #2: Configure Your Kernel
  4. Lesson #3: Compile Your Kernel
  5. Lesson #4: Boot Your New kernel
  6. Lesson #5: Your First printk
  7. Lesson #6: Overview of the Kernel Source
  8. Lesson #7: Understanding System Calls
  9. Lesson #8: Your First kernel Module
  10. Lesson #9: Creating, Applying and Submitting Patches

Visit LinuxChix Kernel Hacking Lessons. for more information.

Ubuntu Release, Maintenance and Support Schedule

Mark Shuttleworth has written a good blog post detailing about future Ubuntu release schedule and the length of support for a particular release, whether its a standard release or an LTS (Long Term Support) release.

In his post, he also explains about the point release concept for the LTS, which each Long Term support installation will receive continuous updates up until the next release of LTS. Which is due to be released in two years time. This point release will allow fresh LTS installation to receives new patches and updates without going through the hassle downloading them through the internet.

Standard releases will continue to receive patches and updates for one and a half-year and Server LTS release will continue to receive updates for 5 years.

For more information read Mark Shuttleworth post, The Art of Release

ssh-vulkey : How to test weak SSH keys on your server

This might be stale news by most security alert people, but I felt compelled to write this post nevertheless. Byy this time most security alert people have realised that a serious security vulnerability has been discovered in the random number generator used by OpenSSL on Debian and Ubuntu systems, and there are a lot of sites have published information about it. [1] [2] [3] [4] [5].

This vulnerability caused OpenSSL to generate “common” and predictable keys, which is easily crackable by using brute-force algorithm. In the extreme case, some of the keys are successfully cracked in 2 hours time. Longer keys 8192-bit RSA keyset might take as short as 129 days to generate as opposed to hundred of years if the keys were generated securely.

Which Ubuntu Linux system are affected ?
As Ubuntu linux operating system is based on Debian, it inherited Debian vulnerability problem. Users who has generated keys under (before updating to the new OpenSSL package via automatic updates, which is before May 13 2008) — Ubuntu 7.04 Ubuntu 7.10 Ubuntu 8.04 LTS are all affected by this vulnerability

Other system which uses the keys generated by Debian and the above mentioned Ubuntu system is also affected as the keys might allow malicious 3rd party user to abuse the system. SSH login which uses these keys will not be considered secure anymore, and are advised to update their SSH keys immediately.

How to check against weak SSH keys ?
A system is as strong as its security measures (in this case, the key) to protect it. By using ssh-vulkey as detailed in Ubuntu Security Notice 612-2, you can detect weak keys in your system, and updates them accordingly.

Run “sudo ssh-vulnkey -a” command to check against weak keys :

ssh-vulnkey -a

ssh-vulnkey -a
Not blacklisted: 2048 fa:2e:1d:a6:84:64:a1:80:c4:31:68:5a:b0:1a:cb:fe /etc/ssh/ssh_host_rsa_key.pub
Not blacklisted: 1024 f4:34:04:85:58:a0:6b:0a:a1:b9:2d:3b:e6:19:5a:76 /etc/ssh/ssh_host_dsa_key.pub
COMPROMISED: 2048 5c:10:8a:c0:55:8c:1f:d9:4b:05:f0:35:0a:0d:2f:5c /home/someuser/.ssh/authorized_keys
Not blacklisted: 2048 a7:b4:3e:41:18:cb:f7:68:5e:4f:ae:30:14:d2:17:fd /home/someuser/.ssh/authorized_keys

More information about OpenSSL in Debian / Ubuntu security vulnerability :

Melayubuntu – the best local Ubuntu blog

Today I would proudly write about a fine, if not the best local Ubuntu blog for Malaysian, Melayubuntu. Best of all, its written in Malay !

The website is filled with loads of Ubuntu tips which is useful for Ubuntu users, whether they are new or an old timer. It is the one particular blog which should be worth subscribing for.