Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Before I disabled the ACPI (because it is not supported by Ubuntu) Ubuntu can't boot (obviously!)

At that time when I boot Ubuntu, I always get these 2 messages. After 1 of those message shows, nothing shows up.

error: "prefix" is not set 
error: "prefix" not found

Although my problem is solved, I just want to know what these 2 messages mean in general, like what makes GRUB show this message. Espically the "prefix" part.

share|improve this question
Impossible without further context. Include surrounding lines or take a photo of the screen and post it. – izx Jun 27 '12 at 12:38
No, that's the only line that appears. And the problem is fixed now so it is impossible to post any screenshot :( – Emerson Hsieh Jun 27 '12 at 15:25
up vote 2 down vote accepted

According to bcbc (who is very knowledgeable about Wubi):

The message about the 'prefix not being set' is innocuous (happens on every 11.04 wubi install on every boot).

Source: Answer #2 to this question on Launchpad.

That is to say that this error message always occurs, even on Wubi systems that are working properly. If you're experiencing (or used to experience) an actual problem, it's actually unrelated to that message.

share|improve this answer
Thanks for the answer! But what does the "prefix" mean? – Emerson Hsieh Aug 18 '12 at 14:50

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.