12.04 LTS Precise

It comes with stable version, 1.4.1. ( Don't worry, 1.4.2 is very close to 1.4.1 )

sudo apt-get install ibus ibus-clutter ibus-gtk ibus-gtk3 ibus-qt4
sudo apt-get install ibus-pinyin # or other engine(s) you want
im-switch -s ibus
# logout and re-login
ibus-setup # add input methods you want

Note:

1. If your IBus icon happen to be missing, use the following command.

   ibus-daemon -drx

2. If you are using Kubuntu, install "gnome-icon-theme" package also.

   sudo apt-get install gnome-icon-theme

11.10 Oneiric

Please compile the latest stable version, 1.4.2, yourself. 

10.04 LTS Lucid

Please compile the old stable version, 1.3.9, yourself. ( 1.3.9 is the latest installable version on 10.04 )

Alternatively, you can use the following PPA: 

sudo add-apt-repository ppa:shawn-p-huang/ppa 
sudo apt-get update
sudo apt-get install ibus ibus-gtk ibus-qt4
sudo apt-get install ibus-pinyin # or other engine(s) you want
im-switch -s ibus
# logout and re-login
ibus-setup # add input methods you want

See Also

• http://wiki.ubuntu.org.cn/IBus (in Chinese)