1DMIDECODE(8) System Manager's Manual DMIDECODE(8)
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6 dmidecode - DMI table decoder
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9 dmidecode [OPTIONS]
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12 dmidecode is a tool for dumping a computer's DMI (some say SMBIOS) ta‐
13 ble contents in a human-readable format. This table contains a descrip‐
14 tion of the system's hardware components, as well as other useful
15 pieces of information such as serial numbers and BIOS revision. Thanks
16 to this table, you can retrieve this information without having to
17 probe for the actual hardware. While this is a good point in terms of
18 report speed and safeness, this also makes the presented information
19 possibly unreliable.
20 The DMI table doesn't only describe what the system is currently made
22 of, it also can report the possible evolutions (such as the fastest
23 supported CPU or the maximal amount of memory supported).
24 SMBIOS stands for System Management BIOS, while DMI stands for Desktop
26 Management Interface. Both standards are tightly related and developed
27 by the DMTF (Desktop Management Task Force).
28 As you run it, dmidecode will try to locate the DMI table. It will
30 first try to read the DMI table from sysfs, and next try reading
31 directly from memory if sysfs access failed. If dmidecode succeeds in
32 locating a valid DMI table, it will then parse this table and display a
33 list of records like this one:
34 Handle 0x0002, DMI type 2, 8 bytes. Base Board Information
36 Manufacturer: Intel
37 Product Name: C440GX+
38 Version: 727281-001
39 Serial Number: INCY92700942
40 Each record has:
42 · A handle. This is a unique identifier, which allows records to refer‐
44 ence each other. For example, processor records usually reference
45 cache memory records using their handles.
46 · A type. The SMBIOS specification defines different types of elements
48 a computer can be made of. In this example, the type is 2, which
49 means that the record contains "Base Board Information".
50 · A size. Each record has a 4-byte header (2 for the handle, 1 for the
52 type, 1 for the size), the rest is used by the record data. This
53 value doesn't take text strings into account (these are placed at the
54 end of the record), so the actual length of the record may be (and is
55 often) greater than the displayed value.
56 · Decoded values. The information presented of course depends on the
58 type of record. Here, we learn about the board's manufacturer, model,
59 version and serial number.
60
62 -d, --dev-mem FILE
63 Read memory from device FILE (default: /dev/mem)
64 -q, --quiet
66 Be less verbose. Unknown, inactive and OEM-specific entries are
67 not displayed. Meta-data and handle references are hidden.
68 -s, --string KEYWORD
70 Only display the value of the DMI string identified by KEYWORD.
71 KEYWORD must be a keyword from the following list: bios-vendor,
72 bios-version, bios-release-date, bios-revision, firmware-revi‐
73 sion, system-manufacturer, system-product-name, system-version,
74 system-serial-number, system-uuid, system-family, baseboard-man‐
75 ufacturer, baseboard-product-name, baseboard-version, baseboard-
76 serial-number, baseboard-asset-tag, chassis-manufacturer, chas‐
77 sis-type, chassis-version, chassis-serial-number, chassis-asset-
78 tag, processor-family, processor-manufacturer, processor-ver‐
79 sion, processor-frequency. Each keyword corresponds to a given
80 DMI type and a given offset within this entry type. Not all
81 strings may be meaningful or even defined on all systems. Some
82 keywords may return more than one result on some systems (e.g.
83 processor-version on a multi-processor system). If KEYWORD is
84 not provided or not valid, a list of all valid keywords is
85 printed and dmidecode exits with an error. This option cannot
86 be used more than once.
87 Note: on Linux, most of these strings can alternatively be read
89 directly from sysfs, typically from files under
90 /sys/devices/virtual/dmi/id. Most of these files are even read‐
91 able by regular users.
92 -t, --type TYPE
94 Only display the entries of type TYPE. TYPE can be either a DMI
95 type number, or a comma-separated list of type numbers, or a
96 keyword from the following list: bios, system, baseboard, chas‐
97 sis, processor, memory, cache, connector, slot. Refer to the DMI
98 TYPES section below for details. If this option is used more
99 than once, the set of displayed entries will be the union of all
100 the given types. If TYPE is not provided or not valid, a list
101 of all valid keywords is printed and dmidecode exits with an
102 error.
103 -H, --handle HANDLE
105 Only display the entry whose handle matches HANDLE. HANDLE is a
106 16-bit integer.
107 -u, --dump
109 Do not decode the entries, dump their contents as hexadecimal
110 instead. Note that this is still a text output, no binary data
111 will be thrown upon you. The strings attached to each entry are
112 displayed as both hexadecimal and ASCII. This option is mainly
113 useful for debugging.
114 --dump-bin FILE
116 Do not decode the entries, instead dump the DMI data to a file
117 in binary form. The generated file is suitable to pass to
118 --from-dump later.
119 --from-dump FILE
121 Read the DMI data from a binary file previously generated using
122 --dump-bin.
123 --no-sysfs
125 Do not attempt to read DMI data from sysfs files. This is mainly
126 useful for debugging.
127 --oem-string N
129 Only display the value of the OEM string number N. The first OEM
130 string has number 1. With special value "count", return the num‐
131 ber of OEM strings instead.
132 -h, --help
134 Display usage information and exit
135 -V, --version
137 Display the version and exit
138 Options --string, --type, --dump-bin and --oem-string determine the
140 output format and are mutually exclusive.
141 Please note in case of dmidecode is run on a system with BIOS that
143 boasts new SMBIOS specification, which is not supported by the tool
144 yet, it will print out relevant message in addition to requested data
145 on the very top of the output. Thus informs the output data is not
146 reliable.
147
149 The SMBIOS specification defines the following DMI types:
150 Type Information
152 ────────────────────────────────────────────
153 0 BIOS
154 1 System
155 2 Baseboard
156 3 Chassis
157 4 Processor
158 5 Memory Controller
159 6 Memory Module
160 7 Cache
161 8 Port Connector
162 9 System Slots
163 10 On Board Devices
164 11 OEM Strings
165 12 System Configuration Options
166 13 BIOS Language
167 14 Group Associations
168 15 System Event Log
169 16 Physical Memory Array
170 17 Memory Device
171 18 32-bit Memory Error
172 19 Memory Array Mapped Address
173 20 Memory Device Mapped Address
174 21 Built-in Pointing Device
175 22 Portable Battery
176 23 System Reset
177 24 Hardware Security
178 25 System Power Controls
179 26 Voltage Probe
180 27 Cooling Device
181 28 Temperature Probe
182 29 Electrical Current Probe
183 30 Out-of-band Remote Access
184 31 Boot Integrity Services
185 32 System Boot
186 33 64-bit Memory Error
187 34 Management Device
188 35 Management Device Component
189 36 Management Device Threshold Data
190 37 Memory Channel
191 38 IPMI Device
192 39 Power Supply
193 40 Additional Information
194 41 Onboard Devices Extended Information
195 42 Management Controller Host Interface
196 Additionally, type 126 is used for disabled entries and type 127 is an
198 end-of-table marker. Types 128 to 255 are for OEM-specific data.
199 dmidecode will display these entries by default, but it can only decode
200 them when the vendors have contributed documentation or code for them.
201 Keywords can be used instead of type numbers with --type. Each keyword
203 is equivalent to a list of type numbers:
204 Keyword Types
207 ──────────────────────────────
208 bios 0, 13
209 system 1, 12, 15, 23, 32
210 baseboard 2, 10, 41
211 chassis 3
212 processor 4
213 memory 5, 6, 16, 17
214 cache 7
215 connector 8
216 slot 9
217 Keywords are matched case-insensitively. The following command lines
219 are equivalent:
220 · dmidecode --type 0 --type 13
222 · dmidecode --type 0,13
224 · dmidecode --type bios
226 · dmidecode --type BIOS
228
230 The binary dump files generated by --dump-bin and read using --from-
231 dump are formatted as follows:
232 · The SMBIOS or DMI entry point is located at offset 0x00. It is
234 crafted to hard-code the table address at offset 0x20.
235 · The DMI table is located at offset 0x20.
237
239 There is some ambiguity about how to interpret the UUID fields prior to
240 SMBIOS specification version 2.6. There was no mention of byte swap‐
241 ping, and RFC 4122 says that no byte swapping should be applied by
242 default. However, SMBIOS specification version 2.6 (and later) explic‐
243 itly states that the first 3 fields of the UUID should be read as lit‐
244 tle-endian numbers (byte-swapped). Furthermore, it implies that the
245 same was already true for older versions of the specification, even
246 though it was not mentioned. In practice, many hardware vendors were
247 not byte-swapping the UUID. So, in order to preserve compatibility, it
248 was decided to interpret the UUID fields according to RFC 4122 (no byte
249 swapping) when the SMBIOS version is older than 2.6, and to interpret
250 the first 3 fields as little-endian (byte-swapped) when the SMBIOS ver‐
251 sion is 2.6 or later. The Linux kernel follows the same logic.
252
254 /dev/mem
255 /sys/firmware/dmi/tables/smbios_entry_point (Linux only)
256 /sys/firmware/dmi/tables/DMI (Linux only)
257
259 More often than not, information contained in the DMI tables is inaccu‐
260 rate, incomplete or simply wrong.
261
263 Alan Cox, Jean Delvare
264
266 biosdecode(8), mem(4), ownership(8), vpddecode(8)
267dmidecode January 2019 DMIDECODE(8)