If you should be a sudoer in ubuntu but somehow the system is broken and you can no longer make administrative changes, follow the procedure below to re-enter the sudoers list.

$ sudo ls
[sudo] password for stephane:
stephane is not in the sudoers file. This incident will be reported.

1. During boot, press and hold the left Shift key, and you should see the GRUB menu.
   
2. Select the entry containing (recovery mode) and wait.
   
3. You should now be presented with a menu. Select:
   remount Remount / read/write and mount all other file systems
   
   
   

If this option doesn't appear or won't work, you can instead choose the root option and use the following command to mount the system partition:
mount -o remount /
or
mount -o rw,remount /

After applying this variation, adding a user to the admin (11.10 and ealrier) or sudo (12.04 and later) group is done like:
adduser username admin # 11.10 and earlier
adduser username sudo # 12.04 and later
​

Using mount

1. Get the Information
Sometimes, devices don't automount, in which case you should try to manually mount them. First, you must know what device you are dealing with and what filesystem it is formatted with. Most flash drives are FAT16 or FAT32 and most external hard disks are NTFS. Type the following: 
sudo fdisk -lFind your device in the list. It is probably something like /dev/sdb1. For more information about filesystems, see LinuxFilesystemsExplained. 


2. Create the Mount Point
Now we need to create a mount point for the device. Let's say we want to call it "external". You can call it whatever you want, but if you use spaces in the name it gets a little more complicated. Instead, use an underscore to separate words (like "my_external"). Create the mount point: 
sudo mkdir /media/external

3. Mount the Drive
We can now mount the drive. Let's say the device is /dev/sdb1, the filesystem is FAT16 or FAT32 (like it is for most USB flash drives), and we want to mount it at /media/external (having already created the mount point): 
sudo mount -t vfat /dev/sdb1 /media/external -o uid=1000,gid=1000,utf8,dmask=027,fmask=137The options following the "-o" give you ownership of the drive, and the masks allow for extra security for file system permissions. If you don't use those extra options you may not be able to read and write the drive with your regular username. 
Otherwise, if the device is formatted with NTFS, run: 
sudo mount -t ntfs-3g /dev/sdb1 /media/external
Note: You must have the ntfs-3g driver installed. See MountingWindowsPartitions for more information.

4. Unmounting the Drive
When you are finished with the device, don't forget to unmount the drive before disconnecting it. Assuming /dev/sdb1 is mounted at /media/external, you can either unmount using the device or the mount point: 
sudo umount /dev/sdb1or: 
sudo umount /media/externalYou cannot unmount from the desktop by right-clicking the icon if the drive was manually mounted. 

This information is taken from https://help.ubuntu.com/community/Mount/USB

It seems that Ubuntu left out the headers, so it cannot recompile with the nVidia driver correctly.

This is what worked for me, install headers & dpkg update.
https://bugs.launchpad.net/ubuntu/+s...s/+bug/1068942

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install linux-headers-generic
# only reason to purge is there are several versions, if you know you have different nVidia use that:
sudp apt-get purge nvidia*
sudo apt-get install nvidia-current
sudo dpkg-reconfigure nvidia-current

Bug reports:
https://bugs.launchpad.net/ubuntu/+s...s/+bug/1068341

https://bugs.launchpad.net/fglrx/+bug/1068456
https://bugs.launchpad.net/ubuntu/+s...y/+bug/1068488
https://bugs.launchpad.net/fglrx/+bug/1068661

In this tutorial we will see how to use FFMEG to convert videos having the MP4 extension to AVI. To install ffmpeg in Ubuntu 11.10 or any older versions of Ubuntu, open the terminal and issue this command:

sudo apt-get install ffmpeg

Next, cd to the folder containing your MP4 files and run this command:

ffmpeg -i filename.mp4 -sameq -vcodec mpeg4 -acodec ac3 output.avi

Replace filename.mp4 with your own MP4 file. The generated avi file will be named output.avi, you can rename it to whatever you want.

That's it!

Evi

An anthropologist offered children of an African tribe a new game. He put a basket full of fruit close to a tree and told them that who would be there first would win and get all the fruits. When he gave them the start signal they all went to the tree together holding hands. They all sat down and enjoyed the delicious fruits. When the anthropologist asked why they had gone together rather than running to see who would win and reach the fruits first they said: "Ubuntu, how can one of us be happy if all the others are sad?"

Ubuntu in the Xhosa culture means: "I am, because you are, and I can only be, if you are."

If you are trying to run a program and get the error message:
"File not found"
while your program is really there and it is not missing, then your problem might be that you are trying to run a 32-bit executable on a 64-bit computer.

The solution is to install the ia32-libs package for backwards 32bit compatibility. Run:

1) dpkg -s ia32-libs ; to check whether the ia32-libs package is installed or not
2) open "Ubuntu Software Center", search for "ia32-libs", click "install"

Vassilis