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I recently installed Ubuntu 10.04 on my MacBook. I have it running smoothly on here, but when I used the same disk to install Ubuntu on a friend's Dell Laptop it isn't working correctly.

After the installation process finished, he logged in and everything ran just fine. However when he shut the computer down and later turned it back on, he can't log on. He's using the same login information as before but he keeps getting an authorization failure. I've had him try using his short username and the full name but neither will work.

Is this a hardware problem because of his computer or did something go wrong with the installation?

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What user accounts are available, at login page? – david6 Nov 23 '11 at 3:01
I think just his account. I don't think there are any guests set up yet. – CaldwellYSR Nov 23 '11 at 3:10
See Eliah Kagan,s answer below. A skilled user, with physical access, can reset the password. This could still be confusion about account names, or not remembering the password set. – david6 Nov 23 '11 at 3:15

2 Answers 2

up vote 1 down vote accepted

Whatever the cause, resetting the password will most likely fix the problem.

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Interesting, I'll get him to give it a shot. – CaldwellYSR Nov 23 '11 at 3:12
Thank you very much, this worked to perfection. – CaldwellYSR Nov 26 '11 at 20:46

You can reset your password using Live CD:

Boot from your Ubuntu Live CD, choosing “Try Ubuntu without any change to your computer” from the boot menu.

Once the system boots, open up a new Terminal and then type in the following command:

sudo fdisk -l

This command is used to tell what device name the hard drive is using, which in most cases should be /dev/sda1, but could be different on your system.

$ sudo fdisk -l

Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000e4165

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048   234440703   117219328   83  Linux

Note the device name having * under Boot column.

Now you’ll need to create a directory to mount the hard drive on.

sudo mkdir /media/dir

Now mount the hard drive in the /media/dir folder.

sudo mount /dev/sda1 /media/dir

Now chroot to the mounting point of your disk

sudo chroot /media/dir

Now you should be able to use the passwd command to change your user account’s password

passwd user-name

Unmount the disk and reboot.

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