Ubuntu Notes

Remove Old Ubuntu Kernels

2010-09-06T18:37:00.001+07:00

Everytime you install a new kernel on Ubuntu, it will not remove the old kernels and you'll still be able to boot into one of those kernels. This feature is useful in case the new kernel doesn't run well after installation.

But, there's also a drawback regarding this. Your grub list will grow longer and your startup menu will fill the whole screen. In order to fix this, open a terminal and type uname -r in the screen, it will produce some text like this:

Run uname -r in terminal

Now, open Synaptic Package Manager and search for linux-image-2. It will show you all kernels available and those you already installed. Choose kernel images that you don't need and click on it, select Mark for Removal. Now apply it and your grub menu should be free from old kernels.

Note: Be careful not to delete your newly installed kernel, it should be the one you see in terminal window after you execute uname -r.

How to Change Default OS on Boot

2010-06-13T10:49:00.001+07:00

If you are using multi OS on the same computer, you are probably using grub as bootloader. It's Ubuntu's default loader.

This grub, makes Ubuntu as default OS to load on boot. If you prefer another OS to load at that stage, Windows - for example, you can configure grub by using gedit:

sudo gedit /etc/default/grub

It will open a gedit editor.



If you change this file, run ‘update-grub’ afterwards to update

# /boot/grub/grub.cfg.



GRUB_DEFAULT=0

#GRUB_HIDDEN_TIMEOUT=0

GRUB_HIDDEN_TIMEOUT_QUIET=true

GRUB_TIMEOUT=10

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash”

GRUB_CMDLINE_LINUX=”"



# Uncomment to disable graphical terminal (grub-pc only)

#GRUB_TERMINAL=console



# The resolution used on graphical terminal

# note that you can use only modes which your graphic card supports via VBE

# you can see them in real GRUB with the command `vbeinfo’

#GRUB_GFXMODE=640×480



# Uncomment if you don’t want GRUB to pass “root=UUID=xxx” parameter to Linux

#GRUB_DISABLE_LINUX_UUID=true



# Uncomment to disable generation of recovery mode menu entrys

#GRUB_DISABLE_LINUX_RECOVERY=”true”

You have to change the value of GRUB_DEFAULT. The default is 0, which represents the first line of the OS list on your computer (numbering starts from 0). So, if your Windows is on the fourth line, you change the number to 3.

If you're looking for a more convenient way to do this, try sudo apt-get install startupmanager, it's a GUI grub configuring tool.

#PS: don't forget to run sudo update-grub after you manualy edited grub config in gedit. You don't have to do this if you're using startupmanager, the GUI version.

How to Open 7zip Files on Ubuntu

2010-06-08T11:36:00.002+07:00

You can open 7zip files on Ubuntu by installing p7zip package first:
sudo apt-get install p7zip

If you have File Roller, when you click on 7zip files in Nautilus, Archive Manager will handle your 7zip file.

Or you can use Command Line Interface (CLI) instead:
$p7zip -d a-7zip-file.7z

How to Run Java .jar File in Ubuntu

2010-05-29T01:10:00.001+07:00

Image via Wikipedia

You can run a .jar file by typing this command:

java -jar java_jar_file.jar

Common mistake is typing the command line without -jar option which produces something like:



MissingFieldException[ The following required field is missing from the launch file: ]

at com.sun.javaws.jnl.XMLFormat.parse(Unknown Source)

at com.sun.javaws.jnl.LaunchDescFactory.buildDescript or(Unknown Source)

at com.sun.javaws.jnl.LaunchDescFactory.buildDescript or(Unknown Source)

at com.sun.javaws.Main.launchApp(Unknown Source)

at com.sun.javaws.Main.continueInSecureThread(Unknown Source)

at com.sun.javaws.Main$1.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

Dropbox for File Synchronization

2010-05-28T07:24:00.002+07:00

I found that Dropbox is a good file synchronization for my desktop. It is useful to keep my work always up-to-date either in my office desktop or my own PC at home. It's not just that, you can use it for other purpose like this or this.

To install it on Ubuntu, just go to this link and select deb package corresponding to your system, either 32bit or 64bit Ubuntu.

avast! Antivirus for Ubuntu

2010-05-27T07:36:00.003+07:00

Virus attacks are common in Windows systems and happen less in Linux systems. But, for prevention, you can install an antivirus in Ubuntu just in case of bad things happened.

One of antivirus that I installed on my Ubuntu system is avast! Antivirus. You can install it with this command:

wget http://files.avast.com/files/linux/avast4workstation_1.3.0-2_i386.deb && sudo dpkg -i avast4workstation_1.3.0-2_i386.deb

Then you can access it in Accessories → avast! Antivirus.

CHM reader untuk Ubuntu

2010-05-26T19:30:00.002+07:00

Ada berbagai jenis CHM (Microsoft Compiled HTML Help) reader yang tersedia untuk sistem operasi Ubuntu, seperti gnochm, xchm, kchmviewer, dan sebagainya. Dari berbagai pilihan tersebut, saya lebih suka menggunakan xchm untuk membaca file Compiled HTML Help dalam Ubuntu.

Ubuntu menggunakan desktop Gnome. Sebenarnya, gnochm lebih didukung oleh Gnome. Namun saya kurang suka menggunakan gnochm karena dari pengalaman saya font yang ditampilkan tidak proporsional. Kadang terlalu besar, kadang terlalu kecil. Selain itu, seringkali gnochm mengalami crash dan aplikasi tertutup dengan paksa.

Saya kemudian mencoba aplikasi CHM reader lain, yaitu xchm. Aplikasi ini lebih bagus dalam menampilkan file CHM dan lebih nyaman digunakan untuk membaca file CHM.

Jika tertarik, anda bisa memasangnya di sistem Ubuntu dengan cara mengetikkan perintah ini di terminal:

sudo apt-get install xchm

Selamat membaca! :-)