How to check Memory size in Linux

ref : http://sysdigg.blogspot.com/2007/12/how-to-check-memory-size-in-linux.html
How to check Memory size in Linux

In all Linux operating Systems memory size can be checked by running dmesg,free, top and using Kernel proc information. Linux is very cool it offers various pre-installed tools and commands to check memory size compared to UNIX Operating systems.

To check memory size in Linux using dmesg, run the following command:

[root@earth ~]# dmesg |grep -i memory

Memory: 4084332k/4653052k available (1868k kernel code, 43456k reserved, 755k data, 180k init, 3211208k highmem)

Running dmesg command in Linux displays memory in kilobytes, on this Linux server total memory size is 4 Gg.For checking memory dmesg command is also available in Solaris and HP-UX.To check memory size in linux using /proc information run following from the command line:

[root@svn ~]# cat /proc/meminfo |grep -i memtotal

MemTotal: 4086484 kB

/proc/meminfo shows total memory size configured as 4086484 displayed in kilobytes (KB).

To check memory size on Linux using free command, run the following:

[root@svn ~]# free

total used free shared buffers cached

Mem: 4086484 4033924 52560 0 71764 3122188

-/+ buffers/cache: 839972 3246512

Swap: 4194216 376 4193840

Free command on linux also displays used,free memory,cached memory ,shared and memory

buffer size. You can use –m option to check Linux memory utilization in megabytes:

[root@svn ~]# free -m

total used free shared buffers cached

Mem: 3990 3523 467 0 69 2649

-/+ buffers/cache: 804 3185

Swap: 4095 1 4094

Linux also comes with top command, top can be run to check real memory size and memory utilization.Top display total memory size,used memory,free memory ,memory buffers size and swap memory utilization :

top - 08:05:36 up 6 days, 16:46, 7 users, load average: 0.07, 0.09, 0.08

Tasks: 131 total, 1 running, 130 sleeping, 0 stopped, 0 zombie

Cpu(s): 4.2% us, 0.5% sy, 0.0% ni, 95.3% id, 0.0% wa, 0.0% hi, 0.0% si

Mem: 4086484k total, 3609956k used, 476528k free, 71752k buffers

Swap: 4194216k total, 1100k used, 4193116k free, 2713504k cached

Ubuntu and fedora linux also comes with package called lshw (list hardware) which provides

detailed information on memory size, how many memory dims available, memory slots free along with other Linux system Hardware information .Run lshw and scroll down to *-memory section :

#lshw |grep

*-memory

description: System Memory

physical id: 39

slot: System board or motherboard

size: 1GB