Vmstat
vmstat (virtual memory statistics) is a computer system monitoring tool that collects and displays summary information about operating system memory, processes, interrupts, paging and block I/O. Users of vmstat can specify a sampling interval which permits observing system activity in near-real time.

The vmstat tool is available on most Unix and Unix-like operating systems, such as FreeBSD, Linux or Solaris.

Syntax
The syntax and output of vmstat often differs slightly between different operating systems.

# vmstat 2 6
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 0  0   2536  21496 185684 1353000    0    0     0    14    1     2  0  0 100  0
 0  0   2536  21496 185684 1353000    0    0     0    28 1030   145  0  0 100  0
 0  0   2536  21496 185684 1353000    0    0     0     0 1026   132  0  0 100  0
 0  0   2536  21520 185684 1353000    0    0     0     0 1033   186  1  0 99  0
 0  0   2536  21520 185684 1353000    0    0     0     0 1024   141  0  0 100  0
 0  0   2536  21584 185684 1353000    0    0     0     0 1025   131  0  0 100  0

In the above example the tool reports every two seconds for six iterations.

We can get the customized or required outputs by using various options with vmstat command.

# vmstat –s     this option is use to get Memory Statistics.

# vmstat –d     this option is use to get Disk Statistics.

See also 
 nmon — a system monitor tool for the AIX and Linux operating systems.
 iostat
 top
 sar

External links 
 
 
 
  Softpanorama vmstat page

Unix software
System monitors