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 di‐
31 rectly 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 --no-quirks
70 Decode everything exactly as it is in the table, without trying
71 to fix up common mistakes or hide irrelevant fields. This mode
72 is primarily aimed at firmware developers.
73 -s, --string KEYWORD
75 Only display the value of the DMI string identified by KEYWORD.
76 It must be a keyword from the following list: bios-vendor,
77 bios-version, bios-release-date, bios-revision,
78 firmware-revision, system-manufacturer, system-product-name,
79 system-version, system-serial-number, system-uuid,
80 system-sku-number, system-family, baseboard-manufacturer,
81 baseboard-product-name, baseboard-version,
82 baseboard-serial-number, baseboard-asset-tag,
83 chassis-manufacturer, chassis-type, chassis-version,
84 chassis-serial-number, chassis-asset-tag, processor-family,
85 processor-manufacturer, processor-version, processor-frequency.
86 Each keyword corresponds to a given DMI type and a given offset
87 within this entry type. Not all strings may be meaningful or
88 even defined on all systems. Some keywords may return more than
89 one result on some systems (e.g. processor-version on a multi-
90 processor system). If KEYWORD is not provided or not valid, a
91 list of all valid keywords is printed and dmidecode exits with
92 an error. This option cannot be used more than once.
93 Note: on Linux, most of these strings can alternatively be read
95 directly from sysfs, typically from files under /sys/de‐
96 vices/virtual/dmi/id. Most of these files are even readable by
97 regular users.
98 -t, --type TYPE
100 Only display the entries of type TYPE. It can be either a DMI
101 type number, or a comma-separated list of type numbers, or a
102 keyword from the following list: bios, system, baseboard,
103 chassis, processor, memory, cache, connector, slot. Refer to
104 the DMI TYPES section below for details. If this option is used
105 more than once, the set of displayed entries will be the union
106 of all the given types. If TYPE is not provided or not valid, a
107 list of all valid keywords is printed and dmidecode exits with
108 an error.
109 -H, --handle HANDLE
111 Only display the entry whose handle matches HANDLE. HANDLE is a
112 16-bit integer.
113 -u, --dump
115 Do not decode the entries, dump their contents as hexadecimal
116 instead. Note that this is still a text output, no binary data
117 will be thrown upon you. The strings attached to each entry are
118 displayed as both hexadecimal and ASCII. This option is mainly
119 useful for debugging.
120 --dump-bin FILE
122 Do not decode the entries, instead dump the DMI data to a file
123 in binary form. The generated file is suitable to pass to
124 --from-dump later. FILE must not exist.
125 --from-dump FILE
127 Read the DMI data from a binary file previously generated using
128 --dump-bin.
129 --no-sysfs
131 Do not attempt to read DMI data from sysfs files. This is mainly
132 useful for debugging.
133 --oem-string N
135 Only display the value of the OEM string number N. The first OEM
136 string has number 1. With special value count, return the number
137 of OEM strings instead.
138 -h, --help
140 Display usage information and exit
141 -V, --version
143 Display the version and exit
144 Options --string, --type, --dump-bin and --oem-string determine the
146 output format and are mutually exclusive.
147 Please note in case of dmidecode is run on a system with BIOS that
149 boasts new SMBIOS specification, which is not supported by the tool
150 yet, it will print out relevant message in addition to requested data
151 on the very top of the output. Thus informs the output data is not re‐
152 liable.
153
155 The SMBIOS specification defines the following DMI types:
156 Type Information
158 ────────────────────────────────────────────
159 0 BIOS
160 1 System
161 2 Baseboard
162 3 Chassis
163 4 Processor
164 5 Memory Controller
165 6 Memory Module
166 7 Cache
167 8 Port Connector
168 9 System Slots
169 10 On Board Devices
170 11 OEM Strings
171 12 System Configuration Options
172 13 BIOS Language
173 14 Group Associations
174 15 System Event Log
175 16 Physical Memory Array
176 17 Memory Device
177 18 32-bit Memory Error
178 19 Memory Array Mapped Address
179 20 Memory Device Mapped Address
180 21 Built-in Pointing Device
181 22 Portable Battery
182 23 System Reset
183 24 Hardware Security
184 25 System Power Controls
185 26 Voltage Probe
186 27 Cooling Device
187 28 Temperature Probe
188 29 Electrical Current Probe
189 30 Out-of-band Remote Access
190 31 Boot Integrity Services
191 32 System Boot
192 33 64-bit Memory Error
193 34 Management Device
194 35 Management Device Component
195 36 Management Device Threshold Data
196 37 Memory Channel
197 38 IPMI Device
198 39 Power Supply
199 40 Additional Information
200 41 Onboard Devices Extended Information
201 42 Management Controller Host Interface
202 Additionally, type 126 is used for disabled entries and type 127 is an
204 end-of-table marker. Types 128 to 255 are for OEM-specific data.
205 dmidecode will display these entries by default, but it can only decode
206 them when the vendors have contributed documentation or code for them.
207 Keywords can be used instead of type numbers with --type. Each keyword
209 is equivalent to a list of type numbers:
210 Keyword Types
213 ──────────────────────────────
214 bios 0, 13
215 system 1, 12, 15, 23, 32
216 baseboard 2, 10, 41
217 chassis 3
218 processor 4
219 memory 5, 6, 16, 17
220 cache 7
221 connector 8
222 slot 9
223 Keywords are matched case-insensitively. The following command lines
225 are equivalent:
226 • dmidecode --type 0 --type 13
228 • dmidecode --type 0,13
230 • dmidecode --type bios
232 • dmidecode --type BIOS
234
236 The binary dump files generated by --dump-bin and read using --from-
237 dump are formatted as follows:
238 • The SMBIOS or DMI entry point is located at offset 0x00. It is
240 crafted to hard-code the table address at offset 0x20.
241 • The DMI table is located at offset 0x20.
243
245 There is some ambiguity about how to interpret the UUID fields prior to
246 SMBIOS specification version 2.6. There was no mention of byte swap‐
247 ping, and RFC 4122 says that no byte swapping should be applied by de‐
248 fault. However, SMBIOS specification version 2.6 (and later) explicitly
249 states that the first 3 fields of the UUID should be read as little-en‐
250 dian numbers (byte-swapped). Furthermore, it implies that the same was
251 already true for older versions of the specification, even though it
252 was not mentioned. In practice, many hardware vendors were not byte-
253 swapping the UUID. So, in order to preserve compatibility, it was de‐
254 cided to interpret the UUID fields according to RFC 4122 (no byte swap‐
255 ping) when the SMBIOS version is older than 2.6, and to interpret the
256 first 3 fields as little-endian (byte-swapped) when the SMBIOS version
257 is 2.6 or later. The Linux kernel follows the same logic.
258
260 /dev/mem
261 /sys/firmware/dmi/tables/smbios_entry_point (Linux only)
262 /sys/firmware/dmi/tables/DMI (Linux only)
263
265 More often than not, information contained in the DMI tables is inaccu‐
266 rate, incomplete or simply wrong.
267
269 Alan Cox, Jean Delvare
270
272 biosdecode(8), mem(4), ownership(8), vpddecode(8)
273dmidecode February 2023 DMIDECODE(8)