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Possible Duplicate:
How to fix “The system is running in low-graphics mode” error?

I am totally new to Linux, and Ubuntu.

I bought ASUS X53E Notebook, erased Windows and installed Ubuntu. First it worked ok.

Then when I started working with it, I opened the terminal, entered sudo chmod 666 /usr and then all the icons from the main panel disappeared + the whole system stopped responding.

I decided to restart the system. When restarted, a message appears:

the system is running in low graphics mode

and below it:

Your screen, graphics card and input device setting could not be detected correctly. You will need to configure it yourself.

But the "OK" button is disabled and if I press any buttons nothing happens.

If I enter Ctrl-Alt-F2 it opens the bash terminal. But there commands sudo or apt-get are not found and it says that permission denied if i try to enter any folder like cd /usr

If I enter the su command it asks for the password I don't know.

When encountering this problem first, I reinstalled the whole Ubuntu. but today it happened again just the same.

What shall I do?

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    What was your intention in doing so?
    – cauon
    Oct 4, 2012 at 14:47
  • I thought that my programs should be installed in that directory. Which directory is usually used to install AMP part of LAMP, java and other applications?
    – John
    Oct 4, 2012 at 16:23
  • To get an idea on what belongs where I'd recommend checking the filesystem documentation.
    – cauon
    Oct 4, 2012 at 16:28
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    Just check the answer of @Anwar. You removed the execution rights in the folder. With no execution rights the applications aren't allowed to run at all. This will corrupt the functionality of your system.
    – cauon
    Oct 4, 2012 at 17:33
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    :) you are welcome. Now I see what you wanted to do! Note: you can edit rights more safely with the +x +r +w options for chmod. For the start they are much more easy to use.
    – cauon
    Oct 4, 2012 at 17:40

2 Answers 2

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You have just corrupted the permission settings of important system files. You won't be able to use the system normally.

By using 666 as permission settings, you successfully removed the execution bit from the /usr/ directory, so no files in it can be accessed. And as far as I know, the unity program resides in /usr/bin directory which is of course failing to execute.

The only option is reinstalling Ubuntu again. And please don't chmod system files without knowing exactly what you were doing.

Check these links:

The last link will give you information about the system files and folders

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  • Could you please specify which directories are the ones never to change permissions?
    – John
    Oct 4, 2012 at 16:24
  • I didn't say you should never change permission. but You should be knowing it before doing. The directories are: all directories without your home . That is /usr/ /bin, /sbin` and such. It is generally ok to change permission in /home/your-username-here directories, since those are your files
    – Anwar
    Oct 4, 2012 at 16:28
  • @ArtemMoskalev you can check the last link, it will give you indication about the system folders
    – Anwar
    Oct 4, 2012 at 16:39
  • non-recursive chmod is easily reversible. You can fix the permissions from a live session
    – Zanna
    May 28, 2017 at 20:06
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After reboot try Ctrl+Alt+F1 or Ctrl+Alt+F2.

Log into console and try sudo chmod 755 /usr.

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  • @Anwar, i've looked at my own filesystem about /usr. And i know that chmod without -R key does not affects on "everything under". So... let's repair /usr because "everything under" is not broken.
    – martini
    Oct 4, 2012 at 18:50
  • I cant see recursion in text showed.
    – martini
    Oct 5, 2012 at 6:15
  • this won't work because sudo is in /usr/bin
    – Zanna
    May 28, 2017 at 20:07

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