how to clear the content in CDRW

To clear a CDRW

~$ cdrecord -v dev=/dev/cdrom blank=fast                          

how to mount a cdrom image

To mount a cdrom image (read only)

 ~$ mount -o loop cdrom.iso /mnt/dir

To know the information of a host name or ip address

To get the information of a hostname whois


~$ whois google.com

How to lists wireless networks in range

 To lists the wireless networks in range

 ~$ iwlist scan

How to set ethernet interface speed manually

To set manually ethernet interface speed

~$ ethtool -- change eth0 autoneg off speed 100 duplex full

How to solve screen resolution problem in Debian

To solve screen resolution problem in Debian. First you have to find the possible resolutions with  xrandr -q

$ xrandr -q

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 1024 x 1024
VGA connected 1024x768+0+0 (normal left inverted right x axis y axis) 270mm x 200mm
1024x768 60.0*
800x600 85.1 75.0
640x480 85.0 85.0 75.0 59.9
720x400 70.1

Now you can set your resolution with command
 $ xrandr -s 1024x768

More Details
 $man xrandr