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 -s, --string KEYWORD
70 Only display the value of the DMI string identified by KEYWORD.
71 It must be a keyword from the following list: bios-vendor,
72 bios-version, bios-release-date, bios-revision,
73 firmware-revision, system-manufacturer, system-product-name,
74 system-version, system-serial-number, system-uuid,
75 system-sku-number, system-family, baseboard-manufacturer,
76 baseboard-product-name, baseboard-version,
77 baseboard-serial-number, baseboard-asset-tag,
78 chassis-manufacturer, chassis-type, chassis-version,
79 chassis-serial-number, chassis-asset-tag, processor-family,
80 processor-manufacturer, processor-version, processor-frequency.
81 Each keyword corresponds to a given DMI type and a given offset
82 within this entry type. Not all strings may be meaningful or
83 even defined on all systems. Some keywords may return more than
84 one result on some systems (e.g. processor-version on a multi-
85 processor system). If KEYWORD is not provided or not valid, a
86 list of all valid keywords is printed and dmidecode exits with
87 an error. This option cannot be used more than once.
88 Note: on Linux, most of these strings can alternatively be read
90 directly from sysfs, typically from files under /sys/de‐
91 vices/virtual/dmi/id. Most of these files are even readable by
92 regular users.
93 -t, --type TYPE
95 Only display the entries of type TYPE. It can be either a DMI
96 type number, or a comma-separated list of type numbers, or a
97 keyword from the following list: bios, system, baseboard,
98 chassis, processor, memory, cache, connector, slot. Refer to
99 the DMI TYPES section below for details. If this option is used
100 more than once, the set of displayed entries will be the union
101 of all the given types. If TYPE is not provided or not valid, a
102 list of all valid keywords is printed and dmidecode exits with
103 an error.
104 -H, --handle HANDLE
106 Only display the entry whose handle matches HANDLE. HANDLE is a
107 16-bit integer.
108 -u, --dump
110 Do not decode the entries, dump their contents as hexadecimal
111 instead. Note that this is still a text output, no binary data
112 will be thrown upon you. The strings attached to each entry are
113 displayed as both hexadecimal and ASCII. This option is mainly
114 useful for debugging.
115 --dump-bin FILE
117 Do not decode the entries, instead dump the DMI data to a file
118 in binary form. The generated file is suitable to pass to
119 --from-dump later.
120 --from-dump FILE
122 Read the DMI data from a binary file previously generated using
123 --dump-bin.
124 --no-sysfs
126 Do not attempt to read DMI data from sysfs files. This is mainly
127 useful for debugging.
128 --oem-string N
130 Only display the value of the OEM string number N. The first OEM
131 string has number 1. With special value count, return the number
132 of OEM strings instead.
133 -h, --help
135 Display usage information and exit
136 -V, --version
138 Display the version and exit
139 Options --string, --type, --dump-bin and --oem-string determine the
141 output format and are mutually exclusive.
142 Please note in case of dmidecode is run on a system with BIOS that
144 boasts new SMBIOS specification, which is not supported by the tool
145 yet, it will print out relevant message in addition to requested data
146 on the very top of the output. Thus informs the output data is not re‐
147 liable.
148
150 The SMBIOS specification defines the following DMI types:
151 Type Information
153 ────────────────────────────────────────────
154 0 BIOS
155 1 System
156 2 Baseboard
157 3 Chassis
158 4 Processor
159 5 Memory Controller
160 6 Memory Module
161 7 Cache
162 8 Port Connector
163 9 System Slots
164 10 On Board Devices
165 11 OEM Strings
166 12 System Configuration Options
167 13 BIOS Language
168 14 Group Associations
169 15 System Event Log
170 16 Physical Memory Array
171 17 Memory Device
172 18 32-bit Memory Error
173 19 Memory Array Mapped Address
174 20 Memory Device Mapped Address
175 21 Built-in Pointing Device
176 22 Portable Battery
177 23 System Reset
178 24 Hardware Security
179 25 System Power Controls
180 26 Voltage Probe
181 27 Cooling Device
182 28 Temperature Probe
183 29 Electrical Current Probe
184 30 Out-of-band Remote Access
185 31 Boot Integrity Services
186 32 System Boot
187 33 64-bit Memory Error
188 34 Management Device
189 35 Management Device Component
190 36 Management Device Threshold Data
191 37 Memory Channel
192 38 IPMI Device
193 39 Power Supply
194 40 Additional Information
195 41 Onboard Devices Extended Information
196 42 Management Controller Host Interface
197 Additionally, type 126 is used for disabled entries and type 127 is an
199 end-of-table marker. Types 128 to 255 are for OEM-specific data.
200 dmidecode will display these entries by default, but it can only decode
201 them when the vendors have contributed documentation or code for them.
202 Keywords can be used instead of type numbers with --type. Each keyword
204 is equivalent to a list of type numbers:
205 Keyword Types
208 ──────────────────────────────
209 bios 0, 13
210 system 1, 12, 15, 23, 32
211 baseboard 2, 10, 41
212 chassis 3
213 processor 4
214 memory 5, 6, 16, 17
215 cache 7
216 connector 8
217 slot 9
218 Keywords are matched case-insensitively. The following command lines
220 are equivalent:
221 • dmidecode --type 0 --type 13
223 • dmidecode --type 0,13
225 • dmidecode --type bios
227 • dmidecode --type BIOS
229
231 The binary dump files generated by --dump-bin and read using --from-
232 dump are formatted as follows:
233 • The SMBIOS or DMI entry point is located at offset 0x00. It is
235 crafted to hard-code the table address at offset 0x20.
236 • The DMI table is located at offset 0x20.
238
240 There is some ambiguity about how to interpret the UUID fields prior to
241 SMBIOS specification version 2.6. There was no mention of byte swap‐
242 ping, and RFC 4122 says that no byte swapping should be applied by de‐
243 fault. However, SMBIOS specification version 2.6 (and later) explicitly
244 states that the first 3 fields of the UUID should be read as little-en‐
245 dian numbers (byte-swapped). Furthermore, it implies that the same was
246 already true for older versions of the specification, even though it
247 was not mentioned. In practice, many hardware vendors were not byte-
248 swapping the UUID. So, in order to preserve compatibility, it was de‐
249 cided to interpret the UUID fields according to RFC 4122 (no byte swap‐
250 ping) when the SMBIOS version is older than 2.6, and to interpret the
251 first 3 fields as little-endian (byte-swapped) when the SMBIOS version
252 is 2.6 or later. The Linux kernel follows the same logic.
253
255 /dev/mem
256 /sys/firmware/dmi/tables/smbios_entry_point (Linux only)
257 /sys/firmware/dmi/tables/DMI (Linux only)
258
260 More often than not, information contained in the DMI tables is inaccu‐
261 rate, incomplete or simply wrong.
262
264 Alan Cox, Jean Delvare
265
267 biosdecode(8), mem(4), ownership(8), vpddecode(8)
268dmidecode January 2019 DMIDECODE(8)