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) ta-
ble contents in a human-readable format. This table contains a descrip-
tion of the system's hardware components, as well as other useful
pieces of information such as serial numbers and BIOS revision. Thanks
to this table, you can retrieve 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 possible 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:
o A handle. This is a unique identifier, which allows records to refer-
ence each other. For example, processor records usually reference
cache memory records using their handles.
o 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".
o 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.
o 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.
-s, --string KEYWORD
Only display the value of the DMI string identified by KEYWORD.
KEYWORD must be a keyword from the following list: bios-vendor,
bios-version, bios-release-date, bios-revision, firmware-revi-
sion, system-manufacturer, system-product-name, system-version,
system-serial-number, system-uuid, system-family, baseboard-man-
ufacturer, baseboard-product-name, baseboard-version, baseboard-
serial-number, baseboard-asset-tag, chassis-manufacturer, chas-
sis-type, chassis-version, chassis-serial-number, chassis-asset-
tag, processor-family, processor-manufacturer, processor-ver-
sion, processor-frequency. Each keyword 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 read-
able by regular users.
-t, --type TYPE
Only display the entries of type TYPE. TYPE can be either a DMI
type number, or a comma-separated list of type numbers, or a
keyword from the following list: bios, system, baseboard, chas-
sis, 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 keywords is printed and dmidecode exits with an
error.
-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 entry 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.
--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 num-
ber 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:
o dmidecode --type 0 --type 13
o dmidecode --type 0,13
o dmidecode --type bios
o dmidecode --type BIOS
BINARY DUMP FILE FORMAT
The binary dump files generated by --dump-bin and read using --from-
dump are formatted as follows:
o The SMBIOS or DMI entry point is located at offset 0x00. It is
crafted to hard-code the table address at offset 0x20.
o 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 swap-
ping, and RFC 4122 says that no byte swapping should be applied by
default. However, SMBIOS specification version 2.6 (and later) explic-
itly states that the first 3 fields of the UUID should be read as lit-
tle-endian numbers (byte-swapped). Furthermore, it implies that the
same was already true for older versions of the specification, even
though it was not mentioned. 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 ver-
sion 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 inaccu-
rate, incomplete or simply wrong.
AUTHORS
Alan Cox, Jean Delvare
SEE ALSO
biosdecode(8), mem(4), ownership(8), vpddecode(8)
dmidecode January 2019 DMIDECODE(8)
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