Table of Contents
Introduction
dmidecode is a command-line utility in Unix and Unix-like operating systems, including Linux. It is used to retrieve and decode the DMI (Desktop Management Interface) data from the DMI table. DMI is a standard framework intended for managing and tracking hardware components in a system. Most modern systems have a DMI table that provides information about the system's hardware components such as the BIOS, system, motherboard, processor, memory, and more.
Typical use cases for dmidecode command:
- Fetching BIOS Information: Retrieving details like the BIOS version, vendor, and release date.
- Identifying System Manufacturer and Model: If you want to know the exact model of a system (useful for driver downloads or replacement parts),
dmidecodecan provide this. - Checking Memory Configuration: You can use
dmidecodeto check how many memory slots your system has, which slots are occupied, the size of each memory module, and even details like memory speed and type. - Processor Details: Retrieve specifics about the system's processor(s), such as speed, cores, threads, and manufacturer.
- Asset Management: By scripting around
dmidecode, one can gather a complete inventory of systems, useful in large IT setups for managing assets. - Hardware Auditing: For scenarios where one needs to verify that a machine meets specific hardware requirements or specifications.
- Documentation: Keeping system configuration documents up-to-date with the actual hardware setup.
Understanding Desktop Management Interface (DMI)
DMI is a framework that manages, maintains, and tracks hardware components in a system. It provides a standardized structure for system information, enabling administrators and software to query and set hardware-related settings. DMI operates at the component level, meaning that it's mainly focused on individual parts of a system, such as the BIOS, motherboard, memory, and other pieces of hardware.
Important DMI Types
The DMI type identifies the type of data a particular DMI table entry represents. Here's a list of some key DMI types:
- Type 0: BIOS
- Information about the system's BIOS.
- Type 1: System
- General information about the system like manufacturer, product name, version, etc.
- Type 2: Base Board (or Module)
- Information about the system's main circuit board, like its manufacturer, version, and serial number.
- Type 3: Chassis
- Details about the system's chassis, including type (e.g., desktop, tower), manufacturer, and security status.
- Type 4: Processor
- Information about the CPU(s) installed on the system.
- Type 5: Memory Controller
- Details about the system's memory controller.
- Type 6: Memory Module
- Information about the memory modules installed on the system.
- Type 7: Cache
- Information about the cache memory of the system.
And so on. There are many DMI types (going up to type 44 as of my last update), each describing a different aspect or component of the system.
Basic usage of dmidecode command
You will need root privileges to execute the dmidecode command. The general syntax of dmidecode command is:
$ sudo dmidecode [option]
If dmidecode command is successfully executed, it prints the following details in the output.
- Handle: It is a unique identifier that allows records to reference each other.
- Type: It provides information about computer elements such as system, baseboard, chassis, processor, etc. A number value denotes each element. For example, if the type is
0, it means that the record contains BIOS information. - Size: It shows the size of each record. Each record contains a 4-byte header (2 for the handle, 1 for the type, 1 for the size). The record data uses the rest.
- Decoded values: It contains the information depending on the type of record. The BIOS information includes details of the vendor, version, release date, ROM size, etc.
Sample Output:
DMI Types
The following are DMI types and their respective information.
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 ... 29 Electrical Current Probe 30 Out-of-band Remote Access31 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
In this article, we will learn how to use dmidecode command to get information about hardware components in Linux systems.
1. Read memory from alternate device file
The --dev-mem option in dmidecode allows you to specify an alternate device file for accessing the system's physical memory.
By default, dmidecode reads the system's DMI (SMBIOS) information directly from the system's physical memory, using the /dev/mem device file. The /dev/mem file represents the system's physical memory, and with appropriate permissions, you can directly access and read from it.
The --dev-mem option lets you override the default /dev/mem path. This could be useful in specialized environments or scenarios where the default memory device is located somewhere other than /dev/mem or when analyzing a memory dump from another machine.
$ sudo dmidecode -d FILE
OR
$ sudo dmidecode --dev-mem FILE
Sample Output:
2. List available DMI 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.
You can just hit dmidecode --type without any TYPE and it should give you the list of supported TYPEs
# dmidecode --type
dmidecode: option '--type' requires an argument
Type number or keyword expected
Valid type keywords are:
bios
system
baseboard
chassis
processor
memory
cache
connector
slot
3. Mapping DMI Type with Type ID
You can check the man page of dmidecode command to get the mapping ID of individual DMI Type. Here is a sample output:
Keyword Types ------------------------------ bios 0, 13 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
Going forward we can either use the keyword or the Type ID with dmidecode --type [KEYWORD|ID] to get more information for the respective component.
4. Display the information using Type ID
In the previous section we got the TYPE ID of individual supported TYPEs. You can use -t or --type option with the type ID to get more information for that component. It displays the information of specified DMI type. If type ID is not provided or not valid, it prints the list of valid keywords and exits with an error.
$ sudo dmidecode -t type_ID
OR
$ sudo dmidecode --type type_ID
For Example, to get information about the system cassis we will use Type ID as 3:
Sample Output:
5. Display system information using TYPE Keyword
In the previous section we used TYPE ID with dmidecode command, you can also use keywords instead of type ID.
$ sudo dmidecode -t keyword
Sample Output:
# dmidecode --type=memory # dmidecode 3.2 Getting SMBIOS data from sysfs. SMBIOS 2.8 present. Handle 0x1000, DMI type 16, 23 bytes Physical Memory Array Location: Other Use: System Memory Error Correction Type: Multi-bit ECC Maximum Capacity: 60 GB Error Information Handle: Not Provided Number Of Devices: 4 Handle 0x1100, DMI type 17, 40 bytes Memory Device Array Handle: 0x1000 Error Information Handle: Not Provided Total Width: Unknown Data Width: Unknown Size: 16384 MB Form Factor: DIMM Set: None Locator: DIMM 0 Bank Locator: Not Specified Type: RAM Type Detail: Other Speed: Unknown Manufacturer: Red Hat Serial Number: Not Specified Asset Tag: Not Specified Part Number: Not Specified Rank: Unknown Configured Memory Speed: Unknown Minimum Voltage: Unknown Maximum Voltage: Unknown Configured Voltage: Unknown ...
6. Display the information about BIOS
The following command displays the BIOS information of your system.
$ sudo dmidecode -t bios
OR
$ sudo dmidecode --type bios
Sample Output:
7. Print the system information
You can use this command to get information about the system's manufacturer, product name, version, and serial number.
$ sudo dmidecode -t system
OR
$ sudo dmidecode --type system
Sample Output:
8. Display the baseboard information
With the following command, you can get the baseboard information of the system.
$ sudo dmidecode -t baseboard
OR
$ sudo dmidecode --type baseboard
Sample Output:
9. Get the information about chassis
To get the information about chassis, you can run the following command.
$ sudo dmidecode -t chassis
Sample Output:
10. Display the information using DMI string keywords
You can use -s or --string option to display the information using DMI string keywords. If keyword is not provided or not valid, it prints the list of valid keywords and exits with an error.
Following are the valid string keywords:
bios-vendor bios-version bios-release-date system-manufacturer system-product-name system-version system-serial-number system-uuid system-family 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
$ sudo dmidecode -s KEYWORD
OR
$ sudo dmidecode --string KEYWORD
Sample Output:
11. Get BIOS version
We can utilise the bios-version string using dmidecode --string bios-version to get the BIOS version of any Linux system:
# dmidecode --string bios-version 1.11.0-2.el7
12. Get BIOS Release Date
We can utilise the bios-release-date string using dmidecode --string bios-release-date command to get the BIOS release date of any Linux server:
# dmidecode --string bios-release-date 04/01/2014 # dmidecode --string bios-release-date 05/21/2018
13. Get System Product Name of Linux Hardware
We can utilise the system-product-name string and can be used as dmidecode --string system-product-name to get the product name on which the Linux server is installed:
# dmidecode --string system-product-name ProLiant BL460c Gen9 # dmidecode --string system-product-name OpenStack Compute
14. Get serial number of your Linux hardware
We can utilise the system-serial-number string and can be used as dmidecode --string system-serial-number to get the serial number of the hardware on which Linux server is installed:
# dmidecode --string system-serial-number SGH709S309 # dmidecode --string system-serial-number 5f7dfa83-de5a-43a4-a8c1-87be1d4a92a8
15. Get processor information of your Linux hardware
You can utilise the processor-version to get the details of the processor available on your Linux server. If your server is having more than one processor then the following command may result in more than one result:
# dmidecode --string processor-version Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz Intel(R) Xeon(R) CPU E5-2640 v3 @ 2.60GHz # dmidecode --string processor-version RHEL 7.6.0 PC (i440FX + PIIX, 1996) RHEL 7.6.0 PC (i440FX + PIIX, 1996)
16. Get processor frequency of your processor
We can also get the processor frequency of the processor used in your Linux server using the following command. Here also if you have more than one processor then you may get multiple result for individual processor:
# dmidecode --string processor-frequency 2000 MHz 2000 MHz # dmidecode --string processor-frequency 2600 MHz 2600 MHz
17. Provide less verbose output
Using -q or --quiet option hides some information in the output. Unknown, inactive, and OEM -specific entries are hidden. It also does not display meta-data and handle references.
$ sudo dmidecode -q
OR
$ sudo dmidecode --quiet
Sample Output:
18. Dump the information as hexadecimal
-u or --dump option does not decode the table contents but dumps the contents as hexadecimal instead. The string values of each entry are displayed as both hexadecimal and ASCII. It can be helpful in debugging.
$ sudo dmidecode -u
OR
$ sudo dmidecode --dump
Sample Output:
19. Dump the DMI data to a file
You can use this command to dump the DMI data into a file in a binary form.
$ sudo dmidecode --dump-bin filename
Sample Output:
20. Read the data from a binary file
To read the data from a binary file previously generated with --dump-bin, you can use the following command.
$ sudo dmidecode --from-dump filename
Sample Output:
Alternatives to dmidecode command
While dmidecode is a prevalent tool for fetching DMI (SMBIOS) information, several other utilities offer similar or complementary functionalities:
- lshw: A comprehensive tool that provides detailed reports about all hardware components in the system.
- hwinfo: Another tool that probes for available hardware in the system and provides detailed information about them.
- inxi: A full-featured system information script that provides an overview of system hardware, software, and system status.
- lscpu: Focuses specifically on CPU architecture. It provides detailed information about the CPU.
- lsblk: Lists information about block devices (like drives) on the system.
- lsusb: Shows information about USB buses and connected USB devices.
- lspci: Displays information about all PCI buses and devices in the system.
- biosdecode: Decodes several different types of BIOS data. It's from the same suite as
dmidecode.
Conclusion
dmidecode stands as an essential tool in the toolkit of system administrators, IT professionals, and hardware enthusiasts. Its ability to directly retrieve and decode DMI/SMBIOS information without relying on the OS's current knowledge of the hardware makes it uniquely positioned to provide accurate and detailed insights about the system's hardware components. While there are alternatives and complementary tools, the specificity and comprehensive nature of the data dmidecode offers make it irreplaceable for certain tasks. Understanding your system down to the component level can be invaluable for troubleshooting, audits, optimizations, or mere curiosity.
What’s Next
5 system tools to monitor network traffic in Linux with examples
Further Reading
man page for dmidecode command
