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dmidecode - DMI
table decoder
dmidecode [OPTIONS]
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 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. If it succeeds, 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:
.- reference each other. For example, processor records
usually reference cache memory records using their handles.
.- a computer can
be made of. In this example, the type is 2, which means that the record
contains "Base Board Information".
.-- 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.
.- of record. Here,
we learn about the board’s manufacturer, model, version and serial number.
- -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,
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. 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.
- -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, 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 keywords is printed
and dmidecode exits with an error.
- -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.
- -h, --help
- Display usage information
and exit
- -V, --version
- Display the version and exit
Options --string, --type and
--dump-bin determine the output format and are mutually exclusive.
The
SMBIOS
specification defines the following DMI
types:
| Type | Information |
| 0 |
| 1 | System |
| 2 | Base
Board |
| 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 Device |
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 |
| 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:
The binary dump files generated by
--dump-bin and read using --from-dump are formatted as follows:
.- It is crafted
to hard-code the table address at offset 0x20.
.-
/dev/mem
More often
than not, information contained in the DMI
tables is inaccurate, incomplete
or simply wrong.
Alan Cox, Jean Delvare
biosdecode(8)
, mem(4)
,
ownership(8)
, vpddecode(8)
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