Open Synaptic package manager, search for ibus-unikey and install it.
Once you’ve completed the install, go to your desktop. Click on System and look for IBus Preferences. There you can configure the settings.
Make sure to open IBus every time you want to type in Vietnamese, and click on the taskbar icon to switch back or turn it off when you don’t.
Once you’re using it, the keyboard shortcuts to make the tones and accents are:
s = sắc (eg. os → ó)
f = huyền (eg. of → ò)
j = nặng (eg. oj → ọ)
r = hỏi (eg. or → ỏ)
x = ngã (ox → õ)
mũ – press the key twice (eg. oo → ô)
móc – letter + w (eg. ow → ơ, aw → ă)
Over to you: Have you used Unikey on Ubuntu? Got any tips?