dmidecode

One of my favourite tools, dmidecode, can be used to dump a computer's desktop management interface (DMI) table. In practice, this means that it can be used to find out what kind of hardware you're running in a machine.

This command requires root access, so we'll be using sudo throughout these examples.

First, we're going to list the valid types we can pass to dmidecode:

$ dmidecode --type
dmidecode: option '--type' requires an argument
Type number or keyword expected
Valid type keywords are:
  bios
  system
  baseboard
  chassis
  processor
  memory
  cache
  connector
  slot

Starting at the top, we're going to use bios and see if it gives us anything useful:

$ sudo dmidecode --type bios
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.5 present.

Handle 0x0000, DMI type 0, 20 bytes
BIOS Information
 Vendor: innotek GmbH
 Version: VirtualBox
 Release Date: 12/01/2006
 Address: 0xE0000
 Runtime Size: 128 kB
 ROM Size: 128 kB
 Characteristics:
 ISA is supported
 PCI is supported
 Boot from CD is supported
 Selectable boot is supported
 8042 keyboard services are supported (int 9h)
 CGA/mono video services are supported (int 10h)
 ACPI is supported

Instantly, we can see VirtualBox next to Version, which is a pretty strong hint that we're dealing with a VM.

Next, we will choose something else, system:

$ sudo dmidecode --type system
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.5 present.

Handle 0x0001, DMI type 1, 27 bytes
System Information
    Manufacturer: innotek GmbH
    Product Name: VirtualBox
    Version: 1.2
    Serial Number: 0
    UUID: BDC643B8-8D4D-4288-BDA4-A72F606CD0EA
    Wake-up Type: Power Switch
    SKU Number: Not Specified
    Family: Virtual Machine

Again, the Product Name seen here is VirtualBox, and the Family is Virtual Machine, both of which are pretty damning pieces of evidence.

Lastly, we're going to look at the Chassis Information:

$ sudo dmidecode --type chassis
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.5 present.

Handle 0x0003, DMI type 3, 13 bytes
Chassis Information
    Manufacturer: Oracle Corporation
    Type: Other
    Lock: Not Present
    Version: Not Specified
    Serial Number: Not Specified
    Asset Tag: Not Specified
    Boot-up State: Safe
    Power Supply State: Safe
    Thermal State: Safe
    Security Status: None

Oracle corporation is, again, a significant piece of information that leads us to believe we're in a virtualized environment.

If we don't want a lot of other information, we can fine-tune our search using dmidecode's -s option.

Running this option without an argument outputs a list of potential arguments we can use:

$ sudo dmidecode -s
dmidecode: option requires an argument -- 's'
String keyword expected
Valid string keywords are:
 bios-vendor
 bios-version
 bios-release-date
 system-manufacturer
 system-product-name
 system-version
 system-serial-number
 system-uuid
 baseboard-manufacturer
 baseboard-product-name
 baseboard-version
 baseboard-serial-number
 baseboard-asset-tag
 chassis-manufacturer
 chassis-type
 chassis-version
 chassis-serial-number
 chassis-asset-tag
 processor-family
 processor-manufacturer
 processor-version
 processor-frequency

Here, we can instantly see bios-version, and as we know from earlier, it should be VirtualBox:

$ sudo dmidecode -s bios-version
VirtualBox

These types of short-output commands are very useful for scripting, where succinctness is sometimes desirable.