dmidecode命令可以让你在Linux系统下获取有关硬件方面的信息。dmidecode的作用是将DMI数据库中的信息解码，以可读的文本方式显示。由于DMI信息可以人为修改，因此里面的信息不一定是系统准确的信息。dmidecode遵循SMBIOS/DMI标准，其输出的信息包括BIOS、系统、主板、处理器、内存、缓存等等。
DMI（Desktop Management Interface,DMI）就是帮助收集电脑系统信息的管理系统，DMI信息的收集必须在严格遵照SMBIOS规范的前提下进行。SMBIOS（System Management BIOS）是主板或系统制造者以标准格式显示产品管理信息所需遵循的统一规范。SMBIOS和DMI是由行业指导机构Desktop Management Task Force(DMTF)起草的开放性的技术标准，其中DMI设计适用于任何的平台和操作系统。
DMI充当了管理工具和系统层之间接口的角色。它建立了标准的可管理系统更加方便了电脑厂商和用户对系统的了解。DMI的主要组成部分是Management Information Format(MIF)数据库。这个数据库包括了所有有关电脑系统和配件的信息。通过DMI，用户可以获取序列号、电脑厂商、串口信息以及其它系统配件信息。
语法
dmidecode [选项]
选项
-d，-DEV MEM文件从设备文件读取内存（默认值：/DEV/MEM）
-h，帮助显示此帮助文本并退出
-Q，安静较少的冗长输出
-s，-string关键字只显示给定的DMI字符串的值
-t，-Type类型只显示给定类型的条目
-U，-转储不解码条目
——转储文件将DMI数据转储到二进制文件中。
——从转储文件读取二进制文件中的DMI数据
-V，-版本显示版本和退出
其实以上数值就是通过dmidecode命令来实现的，具体方法如下：
dmidecode以一种可读的方式dump出机器的DMI(Desktop Management Interface)信息。这些信息包括了硬件以及BIOS，既可以得到当前的配置，也可以得到系统支持的最大配置，比如说支持的最大内存数等。
DMI有人也叫SMBIOS(System Management BIOS)，这两个标准都由DMTF(Desktop Management Task Force)开发。
实例：
显示全部dmi信息:
[root@localhost ~]# dmidecode
# dmidecode 2.12
SMBIOS 2.7 present.
......
......
Handle 0x0020, DMI type 127, 4 bytes
End Of Table
更精简的信息显示：
[root@localhost ~]# dmidecode -q
显示指定类型的信息：
通常我只想查看某类型，比如CPU，内存或者磁盘的信息而不是全部的。这可以使用-t(--type TYPE)来指定信息类型：
[root@localhost ~]# dmidecode -t bios
[root@localhost ~]# dmidecode -t 0,4
dmidecode支持的类型:
Type Information
--------------------------------------------
0 BIOS
1 System
2 Baseboard
3 Chassis
4 Processor
5 Memory Controller
6 Memory Module
7 Cache
8 Port Connector
通过关键字查看信息：
比如只想查看序列号，可以使用:
[root@localhost ~]# dmidecode -s system-serial-number
-s (--string keyword)支持的keyword包括：
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-ver-sion, chassis-serial-number, chassis-asset-tag, processor-family, pro-cessor-manufacturer, processor-version, processor-frequency.
查看当前内存和支持的最大内存:
Linux下，可以使用free或者查看meminfo来获得当前的物理内存：
[root@localhost ~]# free -m
total used free shared buffers cached
Mem: 32053 436 31617 0 8 55
-/+ buffers/cache: 371 31681
Swap: 7999 0 7999
这里显示了当前服务器的物理内存是32GB。
服务器到底能扩展到多大的内存？,可以使用下面的命令来查看:
[root@localhost ~]# dmidecode -t 16
# dmidecode 2.12
SMBIOS 2.7 present.
Handle 0x0007, DMI type 16, 23 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Single-bit ECC
Maximum Capacity: 768 GB (可扩展768G)
Error Information Handle: Not Provided
Number Of Devices: 12
但是，事实不一定如此，因此插槽可能已经插满了。也就是我们还必须查清这里的32G到底是4*8GB, 2*16GB还是其他？
如果是4*8GB，那么尽管可以扩展到768GB，但是插槽已经插满，无法扩展了：
[root@localhost ~]# dmidecode -t 17
1 # dmidecode 2.12 2 SMBIOS 2.7 present. 3 4 Handle 0x0008, DMI type 17, 34 bytes 5 Memory Device 6 Array Handle: 0x0007 7 Error Information Handle: Not Provided 8 Total Width: 72 bits 9 Data Width: 64 bits 10 Size: 16384 MB 11 Form Factor: DIMM 12 Set: None 13 Locator: DIMM010 14 Bank Locator: BRANCH 0 CHANNEL 1 DIMM 0 15 Type: DDR3 16 Type Detail: Synchronous Registered (Buffered) 17 Speed: 1067 MHz 18 Manufacturer: Hynix 19 Serial Number: 0x37161DC3 20 Asset Tag: Unknown 21 Part Number: HMT42GR7CMR4A-G7 22 Rank: 4 23 Configured Clock Speed: 800 MHz 24 25 Handle 0x0009, DMI type 17, 34 bytes 26 Memory Device 27 Array Handle: 0x0007 28 Error Information Handle: Not Provided 29 Total Width: Unknown 30 Data Width: Unknown 31 Size: No Module Installed 32 Form Factor: DIMM 33 Set: None 34 Locator: DIMM011 35 Bank Locator: BRANCH 0 CHANNEL 1 DIMM 1 36 Type: DDR3 37 Type Detail: Synchronous 38 Speed: Unknown 39 Manufacturer: NO DIMM 40 Serial Number: NO DIMM 41 Asset Tag: NO DIMM 42 Part Number: NO DIMM 43 Rank: Unknown 44 Configured Clock Speed: Unknown 45 46 Handle 0x000A, DMI type 17, 34 bytes 47 Memory Device 48 Array Handle: 0x0007 49 Error Information Handle: Not Provided 50 Total Width: Unknown 51 Data Width: Unknown 52 Size: No Module Installed 53 Form Factor: DIMM 54 Set: None 55 Locator: DIMM020 56 Bank Locator: BRANCH 0 CHANNEL 2 DIMM 0 57 Type: DDR3 58 Type Detail: Synchronous 59 Speed: Unknown 60 Manufacturer: NO DIMM 61 Serial Number: NO DIMM 62 Asset Tag: NO DIMM 63 Part Number: NO DIMM 64 Rank: Unknown 65 Configured Clock Speed: Unknown 66 67 Handle 0x000B, DMI type 17, 34 bytes 68 Memory Device 69 Array Handle: 0x0007 70 Error Information Handle: Not Provided 71 Total Width: Unknown 72 Data Width: Unknown 73 Size: No Module Installed 74 Form Factor: DIMM 75 Set: None 76 Locator: DIMM021 77 Bank Locator: BRANCH 0 CHANNEL 2 DIMM 1 78 Type: DDR3 79 Type Detail: Synchronous 80 Speed: Unknown 81 Manufacturer: NO DIMM 82 Serial Number: NO DIMM 83 Asset Tag: NO DIMM 84 Part Number: NO DIMM 85 Rank: Unknown 86 Configured Clock Speed: Unknown 87 88 Handle 0x000C, DMI type 17, 34 bytes 89 Memory Device 90 Array Handle: 0x0007 91 Error Information Handle: Not Provided 92 Total Width: Unknown 93 Data Width: Unknown 94 Size: No Module Installed 95 Form Factor: DIMM 96 Set: None 97 Locator: DIMM030 98 Bank Locator: BRANCH 0 CHANNEL 3 DIMM 0 99 Type: DDR3 100 Type Detail: Synchronous 101 Speed: Unknown 102 Manufacturer: NO DIMM 103 Serial Number: NO DIMM 104 Asset Tag: NO DIMM 105 Part Number: NO DIMM 106 Rank: Unknown 107 Configured Clock Speed: Unknown 108 109 Handle 0x000D, DMI type 17, 34 bytes 110 Memory Device 111 Array Handle: 0x0007 112 Error Information Handle: Not Provided 113 Total Width: Unknown 114 Data Width: Unknown 115 Size: No Module Installed 116 Form Factor: DIMM 117 Set: None 118 Locator: DIMM031 119 Bank Locator: BRANCH 0 CHANNEL 3 DIMM 1 120 Type: DDR3 121 Type Detail: Synchronous 122 Speed: Unknown 123 Manufacturer: NO DIMM 124 Serial Number: NO DIMM 125 Asset Tag: NO DIMM 126 Part Number: NO DIMM 127 Rank: Unknown 128 Configured Clock Speed: Unknown 129 130 Handle 0x000E, DMI type 17, 34 bytes 131 Memory Device 132 Array Handle: 0x0007 133 Error Information Handle: Not Provided 134 Total Width: 72 bits 135 Data Width: 64 bits 136 Size: 16384 MB 137 Form Factor: DIMM 138 Set: None 139 Locator: DIMM110 140 Bank Locator: BRANCH 1 CHANNEL 1 DIMM 0 141 Type: DDR3 142 Type Detail: Synchronous Registered (Buffered) 143 Speed: 1067 MHz 144 Manufacturer: Hynix 145 Serial Number: 0x37A61E5F 146 Asset Tag: Unknown 147 Part Number: HMT42GR7CMR4A-G7 148 Rank: 4 149 Configured Clock Speed: 800 MHz 150 151 Handle 0x000F, DMI type 17, 34 bytes 152 Memory Device 153 Array Handle: 0x0007 154 Error Information Handle: Not Provided 155 Total Width: Unknown 156 Data Width: Unknown 157 Size: No Module Installed 158 Form Factor: DIMM 159 Set: None 160 Locator: DIMM111 161 Bank Locator: BRANCH 1 CHANNEL 1 DIMM 1 162 Type: DDR3 163 Type Detail: Synchronous 164 Speed: Unknown 165 Manufacturer: NO DIMM 166 Serial Number: NO DIMM 167 Asset Tag: NO DIMM 168 Part Number: NO DIMM 169 Rank: Unknown 170 Configured Clock Speed: Unknown 171 172 Handle 0x0010, DMI type 17, 34 bytes 173 Memory Device 174 Array Handle: 0x0007 175 Error Information Handle: Not Provided 176 Total Width: Unknown 177 Data Width: Unknown 178 Size: No Module Installed 179 Form Factor: DIMM 180 Set: None 181 Locator: DIMM120 182 Bank Locator: BRANCH 1 CHANNEL 2 DIMM 0 183 Type: DDR3 184 Type Detail: Synchronous 185 Speed: Unknown 186 Manufacturer: NO DIMM 187 Serial Number: NO DIMM 188 Asset Tag: NO DIMM 189 Part Number: NO DIMM 190 Rank: Unknown 191 Configured Clock Speed: Unknown 192 193 Handle 0x0011, DMI type 17, 34 bytes 194 Memory Device 195 Array Handle: 0x0007 196 Error Information Handle: Not Provided 197 Total Width: Unknown 198 Data Width: Unknown 199 Size: No Module Installed 200 Form Factor: DIMM 201 Set: None 202 Locator: DIMM121 203 Bank Locator: BRANCH 1 CHANNEL 2 DIMM 1 204 Type: DDR3 205 Type Detail: Synchronous 206 Speed: Unknown 207 Manufacturer: NO DIMM 208 Serial Number: NO DIMM 209 Asset Tag: NO DIMM 210 Part Number: NO DIMM 211 Rank: Unknown 212 Configured Clock Speed: Unknown 213 214 Handle 0x0012, DMI type 17, 34 bytes 215 Memory Device 216 Array Handle: 0x0007 217 Error Information Handle: Not Provided 218 Total Width: Unknown 219 Data Width: Unknown 220 Size: No Module Installed 221 Form Factor: DIMM 222 Set: None 223 Locator: DIMM130 224 Bank Locator: BRANCH 1 CHANNEL 3 DIMM 0 225 Type: DDR3 226 Type Detail: Synchronous 227 Speed: Unknown 228 Manufacturer: NO DIMM 229 Serial Number: NO DIMM 230 Asset Tag: NO DIMM 231 Part Number: NO DIMM 232 Rank: Unknown 233 Configured Clock Speed: Unknown 234 235 Handle 0x0013, DMI type 17, 34 bytes 236 Memory Device 237 Array Handle: 0x0007 238 Error Information Handle: Not Provided 239 Total Width: Unknown 240 Data Width: Unknown 241 Size: No Module Installed 242 Form Factor: DIMM 243 Set: None 244 Locator: DIMM131 245 Bank Locator: BRANCH 1 CHANNEL 3 DIMM 1 246 Type: DDR3 247 Type Detail: Synchronous 248 Speed: Unknown 249 Manufacturer: NO DIMM 250 Serial Number: NO DIMM 251 Asset Tag: NO DIMM 252 Part Number: NO DIMM 253 Rank: Unknown 254 Configured Clock Speed: Unknown
根据上面输出可以发现，如果要扩展，只有将上面的内存条换成64GB的，才能达到12*64GB=768GB的最大支持内存。
附录：
dmidecode支持的数字参数：
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