manually updating java in ubuntu

Below is outlined the process of updating to the latest JDK in ubuntu and updating the alternatives link manually to point the the latest java:

Step 1: Download:

wget http://download.oracle.com/otn-pub/java/jdk/7u15-b03/jdk-7u15-linux-x64.tar.gz
cd /usr/lib/jvm/
tar -xzf ~/downloads/jdk-7u15-linux-x64.tar.gz

Step 2: If java-7-sun already exists, the below is all that is needed if not skip to step 3 if this is the first time it is setup:

unlink java-7-sun
ln -s jdk1.7.0_15 java-7-sun

Step 3: If java-7-sun link does not already exists:

ln -s jdk1.7.0_15 java-7-sun
update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/java-7-sun/bin/java" 1
update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/java-7-sun/bin/javac" 1
update-alternatives --install "/usr/lib/mozilla/plugins/libjavaplugin.so" "mozilla-javaplugin.so" "/usr/lib/jvm/java-7-sun/jre/lib/amd64/libnpjp2.so" 1
update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/java-7-sun/bin/javaws" 1

Step 4: Choose the java just installed as default:

update-alternatives --config java
update-alternatives --config javac
update-alternatives --config javaws
update-alternatives --config mozilla-javaplugin.so

Wireless Ad-Hoc connection sharing in Ubuntu 10.10

  • dnsmasq-base has to be installed:

    sudo apt-get install dnsmasq-base

  • Remove dnsmasq because it conflicts with NetworkManager:

    sudo apt-get remove dnsmasq

  • Restart NetworkManager:

    sudo /etc/init.d/network-manager restart

  • Add a new wireless network with NetworkManager (left-click on NetworkManager icon, then select "Create New Wireless Network").
  • Set encryption to WEP 40/128-bit Key with a 13 characters key. (Note: You may have to experiment here according to what type of encryption with ad-hoc the device supports. WPA is not supported).
  • NetworkManager now should connect to itself (which means it creates the ad-hoc wireless network and routes any Internet traffic to your wired network interface). Now, connect with the client(s), and you should have a working Internet connection.
  • You have to make sure that this connection is shared to other computers and devices (clients). Make sure that the Connect automatically check-box is selected and on the IPv4 Settings tab make sure that the Method option is set to "Shared to other computers".

HP Deskjet F2430 printing in Ubuntu-9.10

Although the printer HP Deskjet F2430 was automatically detected upon usb connection to my ubuntu-9.10 desktop, the 3.9.8 version of hplip that came via apt repository did not quite get printing to work.

I headed off to hplipopensource.com, downloaded and installed the latest driver (version 3.9.12 as of this writing) and got the all-in-one printer to work just following the install wizard.

I have yet to test the scanner... but that's going to be another update.

sysstat in ubuntu

If you apt-get install sysstat, and sar returns:

Cannot open /var/log/sysstat/sa27: No such file or directory

Sar needs to be enabled before it can be used. The error message in this case is completely useless, and the solution I have found is as below:

Enable sysstat data collection by doing

# dpkg-reconfigure sysstat

or manually by changing value of ENABLED from "false" to "true" in "/etc/default/sysstat".

Then start sysstat via:

# /etc/init.d/sysstat start

Check "/var/log/sysstat/" for the missing file.

Run sar after about 10 minutes to see the collected data.

# sar -A

Debian / Ubuntu command notes for packages and service maintenance ...


  • Clean up non-existent data
    # apt-get autoclean
  • Update list
    # apt-get update
  • Install/update a package
    # apt-get install <pkg>
  • review dist-upgrade prior:
    # apt-get -Vsu -o Debug::pkgProblemResolver=yes dist-upgrade
  • Apply updates
    # apt-get -Vu upgrade
  • Upgrade all dependencies
    # apt-get -Vu dist-upgrade
  • Search cache
    # apt-cache search <pkg>
  • Remove and purge packages
    # apt-get --purge remove <pkg>


  • Install/Update package
    # dpkg -i <pgk>
  • Check listing of installed packages
    # dpkg -l *<pkg>*
  • file belongs to
    # dpkg --search /path/to/file
  • List of file in package
    #dpkg -L <pkg>
  • Info about package
    # dpkg -s <pkg>


  • Manage services at init levels.
    # sysv-rc-conf
    # update-rc.d

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