I will start from the beginning.

I was a noob and ran a really bad command in Ubuntu and now I can't do anything with sudo.

I ran:

sudo chmod 644 /

I was instructed to boot from a liveCD or liveUSB. I chose USB because I still have the one from when I installed it.

I was told to run this from within the booted liveUSB:

sudo chmod 755 / 

And it should be fixed. Well it's not. My best guess is because I am changing the permissions on the root directory of the USB and not the root directory of my laptop.

What am I missing here? How can I fix this?

1 Answer 1


You are right, if you did that, you changed the mode of / of the live-system, but you want to change the mode of / of your root-partition on your hard-disk, so you first need to mount your hard-disk.

Assuming your root-partition is /dev/sda2, enter

mount /dev/sda2 /mnt

to mount your root-partition to /mnt. Then change to that mount-point and change the permissions:

cd /mnt && chmod 755 .

If you are still experiencing problems, a more detailed explanation would be helpful.

  • Is there anyway to get a list of mountable drives? I don't remember what my partition is.
    – wesleywmd
    Dec 5, 2014 at 17:06
  • I'm getting an error : mount: you must specify the file system type
    – wesleywmd
    Dec 5, 2014 at 17:11
  • 1
    Use fdisk -l to see all attached devices and partitions. Using this I determined I need to mount sda5 not sda2.
    – wesleywmd
    Dec 5, 2014 at 18:17

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