You are using debian on Dell or HP servers if you want to know the serialnumber and model you can use the following procedure.This is verr useful when you are connected remotely and find the details.
Dump Desktop Management Interface data.The Desktop Management Interface provides a standardized description of a computer's hardware, including characteristics such as BIOS serial number and hardware connectors. dmidecode provides a dump of the DMI data available from the BIOS. It is used as a back-end tool by other hardware detection programs.
Install dmidecode using the following command
#aptitude install dmidecode
This will complete the installation
Once installed, all you have to do is execute
To Find the service tag use the following command
# dmidecode -s chassis-serial-number
you will get your service tag printed on screen.
To Find the model number use the following command
# dmidecode -s system-product-name