How to find out physical memory?

[kentzhou]

I am beginner on Linux.

I installed CentOS with virtualbox. At the time to create this VM, I assigned 2G(2048M) memory for this VM. My host PC has 8G memory.

After installed CentOS, I start it, then I check the memory with ''free -m", the out put for Total Mem is 1877.
It is not 2048. Anything wrong? how to find out the physical memory of the machine to host Linux?

 

[ryanvade]

171 Mb is probably being used for Graphics memory. But for more info:

cat /proc/meminfo

even better:

egrep --color 'Mem|Cache|Swap' /proc/meminfo

or

 free -t -m

or

vmstat

or

htop

or

top

 

[kentzhou]

thanks. Actually, all of then give me same result except display the data in different way:
total memory 1922448 kb = 1877M

 

[ryanvade]

Yeah, probably just taking into account the graphics memory.

 

[MikeyD]

Yeah it just prints usable memory for your machine. Just running the OS itself takes up memory, so Linux is just giving you the usable memory for your system.
Windows does the same thing: