Manual: dmidecode
DMIDECODE(8) System Manager's Manual DMIDECODE(8)
NAME
dmidecode - DMI table decoder
SYNOPSIS
dmidecode [OPTIONS]
DESCRIPTION
dmidecode is a tool for dumping a computer's DMI (some say SMBIOS) table contents in a human-readable
format. This table contains a description of the system's hardware components, as well as other use‐
ful pieces of information such as serial numbers and BIOS revision. Thanks to this table, you can re‐
trieve this information without having to probe for the actual hardware. While this is a good point
in terms of report speed and safeness, this also makes the presented information possibly unreliable.
The DMI table doesn't only describe what the system is currently made of, it also can report the pos‐
sible evolutions (such as the fastest supported CPU or the maximal amount of memory supported).
SMBIOS stands for System Management BIOS, while DMI stands for Desktop Management Interface. Both
standards are tightly related and developed by the DMTF (Desktop Management Task Force).
As you run it, dmidecode will try to locate the DMI table. It will first try to read the DMI table
from sysfs, and next try reading directly from memory if sysfs access failed. If dmidecode succeeds
in locating a valid DMI table, it will then parse this table and display a list of records like this
one:
Handle 0x0002, DMI type 2, 8 bytes. Base Board Information
Manufacturer: Intel
Product Name: C440GX+
Version: 727281-001
Serial Number: INCY92700942
Each record has:
• A handle. This is a unique identifier, which allows records to reference each other. For example,
processor records usually reference cache memory records using their handles.
• A type. The SMBIOS specification defines different types of elements a computer can be made of. In
this example, the type is 2, which means that the record contains "Base Board Information".
• A size. Each record has a 4-byte header (2 for the handle, 1 for the type, 1 for the size), the
rest is used by the record data. This value doesn't take text strings into account (these are
placed at the end of the record), so the actual length of the record may be (and is often) greater
than the displayed value.
• Decoded values. The information presented of course depends on the type of record. Here, we learn
about the board's manufacturer, model, version and serial number.
OPTIONS
-d, --dev-mem FILE
Read memory from device FILE (default: /dev/mem)
-q, --quiet
Be less verbose. Unknown, inactive and OEM-specific entries are not displayed. Meta-data and
handle references are hidden.
--no-quirks
Decode everything exactly as it is in the table, without trying to fix up common mistakes or
hide irrelevant fields. This mode is primarily aimed at firmware developers.
-s, --string KEYWORD
Only display the value of the DMI string identified by KEYWORD. It must be a keyword from the
following list: bios-vendor, bios-version, bios-release-date, bios-revision,
firmware-revision, system-manufacturer, system-product-name, system-version,
system-serial-number, system-uuid, system-sku-number, system-family, 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. Each key‐
word corresponds to a given DMI type and a given offset within this entry type. Not all
strings may be meaningful or even defined on all systems. Some keywords may return more than
one result on some systems (e.g. processor-version on a multi-processor system). If KEYWORD
is not provided or not valid, a list of all valid keywords is printed and dmidecode exits with
an error. This option cannot be used more than once.
Note: on Linux, most of these strings can alternatively be read directly from sysfs, typically
from files under /sys/devices/virtual/dmi/id. Most of these files are even readable by regu‐
lar users.
--list-strings
List available string keywords, which can then be passed to the --string option.
-t, --type TYPE
Only display the entries of type TYPE. It can be either a DMI type number, or a comma-separat‐
ed list of type numbers, or a keyword from the following list: bios, system, baseboard,
chassis, processor, memory, cache, connector, slot. Refer to the DMI TYPES section below for
details. If this option is used more than once, the set of displayed entries will be the
union of all the given types. If TYPE is not provided or not valid, a list of all valid key‐
words is printed and dmidecode exits with an error.
--list-types
List available type keywords, which can then be passed to the --type option.
-H, --handle HANDLE
Only display the entry whose handle matches HANDLE. HANDLE is a 16-bit integer.
-u, --dump
Do not decode the entries, dump their contents as hexadecimal instead. Note that this is
still a text output, no binary data will be thrown upon you. The strings attached to each en‐
try are displayed as both hexadecimal and ASCII. This option is mainly useful for debugging.
--dump-bin FILE
Do not decode the entries, instead dump the DMI data to a file in binary form. The generated
file is suitable to pass to --from-dump later. FILE must not exist.
--from-dump FILE
Read the DMI data from a binary file previously generated using --dump-bin.
--no-sysfs
Do not attempt to read DMI data from sysfs files. This is mainly useful for debugging.
--oem-string N
Only display the value of the OEM string number N. The first OEM string has number 1. With
special value count, return the number of OEM strings instead.
-h, --help
Display usage information and exit
-V, --version
Display the version and exit
Options --string, --type, --dump-bin and --oem-string determine the output format and are mutually
exclusive.
Please note in case of dmidecode is run on a system with BIOS that boasts new SMBIOS specification,
which is not supported by the tool yet, it will print out relevant message in addition to requested
data on the very top of the output. Thus informs the output data is not reliable.
DMI TYPES
The SMBIOS specification defines the following DMI types:
Type Information
────────────────────────────────────────────
0 BIOS
1 System
2 Baseboard
3 Chassis
4 Processor
5 Memory Controller
6 Memory Module
7 Cache
8 Port Connector
9 System Slots
10 On Board Devices
11 OEM Strings
12 System Configuration Options
13 BIOS Language
14 Group Associations
15 System Event Log
16 Physical Memory Array
17 Memory Device
18 32-bit Memory Error
19 Memory Array Mapped Address
20 Memory Device Mapped Address
21 Built-in Pointing Device
22 Portable Battery
23 System Reset
24 Hardware Security
25 System Power Controls
26 Voltage Probe
27 Cooling Device
28 Temperature Probe
29 Electrical Current Probe
30 Out-of-band Remote Access
31 Boot Integrity Services
32 System Boot
33 64-bit Memory Error
34 Management Device
35 Management Device Component
36 Management Device Threshold Data
37 Memory Channel
38 IPMI Device
39 Power Supply
40 Additional Information
41 Onboard Devices Extended Information
42 Management Controller Host Interface
Additionally, type 126 is used for disabled entries and type 127 is an end-of-table marker. Types 128
to 255 are for OEM-specific data. dmidecode will display these entries by default, but it can only
decode them when the vendors have contributed documentation or code for them.
Keywords can be used instead of type numbers with --type. Each keyword is equivalent to a list of
type numbers:
Keyword Types
──────────────────────────────
bios 0, 13
system 1, 12, 15, 23, 32
baseboard 2, 10, 41
chassis 3
processor 4
memory 5, 6, 16, 17
cache 7
connector 8
slot 9
Keywords are matched case-insensitively. The following command lines are equivalent:
• dmidecode --type 0 --type 13
• dmidecode --type 0,13
• dmidecode --type bios
• dmidecode --type BIOS
BINARY DUMP FILE FORMAT
The binary dump files generated by --dump-bin and read using --from-dump are formatted as follows:
• The SMBIOS or DMI entry point is located at offset 0x00. It is crafted to hard-code the table ad‐
dress at offset 0x20.
• The DMI table is located at offset 0x20.
UUID FORMAT
There is some ambiguity about how to interpret the UUID fields prior to SMBIOS specification version
2.6. There was no mention of byte swapping, and RFC 4122 says that no byte swapping should be applied
by default. However, SMBIOS specification version 2.6 (and later) explicitly states that the first 3
fields of the UUID should be read as little-endian numbers (byte-swapped). Furthermore, it implies
that the same was already true for older versions of the specification, even though it was not men‐
tioned. In practice, many hardware vendors were not byte-swapping the UUID. So, in order to preserve
compatibility, it was decided to interpret the UUID fields according to RFC 4122 (no byte swapping)
when the SMBIOS version is older than 2.6, and to interpret the first 3 fields as little-endian
(byte-swapped) when the SMBIOS version is 2.6 or later. The Linux kernel follows the same logic.
FILES
/dev/mem
/sys/firmware/dmi/tables/smbios_entry_point (Linux only)
/sys/firmware/dmi/tables/DMI (Linux only)
BUGS
More often than not, information contained in the DMI tables is inaccurate, incomplete or simply
wrong.
AUTHORS
Alan Cox, Jean Delvare
SEE ALSO
biosdecode(8), mem(4), ownership(8), vpddecode(8)
dmidecode February 2023 DMIDECODE(8)