This is an user contributed article.
When it is time to upgrade the memory on a Linux host, it is important to understand the existing memory information of the system, which will help to plan the memory upgrade appropriately without opening server chassis (especially, when you have Linux rack mount server).
What is the current total RAM used in the system?
This can be obtained using free command or from the /proc/meminfo file as shown below. In this example, the current RAM is 1GB.
# free
Sample output:
total used free shared buffers cached Mem: 2074016 2002592 71424 0 480908 937296 -/+ buffers/cache: 584388 1489628 Swap: 1951888 79116 1872772
You can also display memory ram, info using /proc file, enteR:
# grep MemTotal /proc/meminfo
Sample output:
MemTotal: 1034624 kB
What is the maximum RAM supported by the system?
You can use dmidecode command to query all memory related information from the system DMI table. In this example, the maximum RAM supported by the system is 8 GB as shown below.
# dmidecode -t 16
Sample output:
# dmidecode 2.9 SMBIOS 2.3 present. Handle 0x1000, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: Multi-bit ECC Maximum Capacity: 8 GB Error Information Handle: Not Provided Number Of Devices: 4
How many memory slots are available for expansion? We know the current memory of the system is 1G. Is this 1 x 1G (or) 2 x 512MB (or) 4 x 256MB? This can be figured out as shown below. In the example below, the system has 4 memory slots and it has 2 x 512MB. If you have to expand upto 8GB of maximum RAM, you need to remove the 512MB from slot 1 and 2, and use 2GB RAM on all the 4 memory slots. This information will give sufficient ideas to plan for RAM expansion accordingly.
# dmidecode -t 17 | grep Size
Sample output:
Size: 512 MB
Size: 512 MB
Size: No Module Installed
Size: No Module Installed
References:
dmidecode can also be used to identify details about several other hardware related information. dmidecode command reads the systems DMI table for the hardware and BIOS information. DMI stands for Desktop Management interface and SMBIOS stands for System Management BIOS.
Distributed Management Task Force maintains the DMI and SMBIOS specification:
- DMI Specification
- SMBIOS Specification
- man pages - dmidecode, free and proc
This article was written by Ramesh Natarajan. At the The Geek Stuff blog he shares his knowledge and experience on Linux and other Geeky stuff. He has more than 15 years of experience in IT industry and has performed very intensive work on Linux system administration, DBA, Hardware and Storage. nixCraft welcomes readers' tips / howtos.
- Email this to a friend
- Printable version
- Rss Feed
- Last Updated: Jul/24/2008
{ 5 comments… read them below or add one }
Cool… I was googling the web yesterday for this info and couldn’t find it! and voila.. all written! thanks :-)
i was planning to expand my ram memory.. had been thinking to buy new ram and thanks for the article it really helped in getting to know the stuff inside.
Hello ev1;
great articule and great command, but in several of my server im receiving on the output ie:
[root@server1 ~]# dmidecode –type 17
–type: No such file or directory
[root@server1 ~]# dmidecode –type 11
–type: No such file or directory
neither with;
[root@server1 ~]# dmidecode processor
processor: No such file or directory
HOw can i fix it ?, i was googling but nothing
good.
Thanks!.
Dear Guille,
You should use either -t or –type, but never -type with single dash (that is indeed incorrect). You can see dmidecode’s help screen by executing it with –help as an argument (alternatively, you can read the manual page: man dmidecode). If you are unsure about what to do then simply execute dmidecode without any arguments at all.
Kindest regards,
Krzysztof
Very useful stuff – any way to differentiate between SDRAM, DDR, DDR2, DDR3?