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A.8. vmstat

Vmstat outputs reports on your system's processes, memory, paging, block input/output, interrupts, and CPU activity. It provides an instantaneous report of the average of these events since the machine was last booted, or since the previous report.
-a
Displays active and inactive memory.
-f
Displays the number of forks since boot. This includes the fork, vfork, and clone system calls, and is equivalent to the total number of tasks created. Each process is represented by one or more tasks, depending on thread usage. This display does not repeat.
-m
Displays slab information.
-n
Specifies that the header will appear once, not periodically.
-s
Displays a table of various event counters and memory statistics. This display does not repeat.
delay
The delay between reports in seconds. If no delay is specified, only one report is printed, with the average values since the machine was last booted.
count
The number of times to report on the system. If no count is specified and delay is defined, vmstat reports indefinitely.
-d
Displays disk statistics.
-p
Takes a partition name as a value, and reports detailed statistics for that partition.
-S
Defines the units output by the report. Valid values are k (1000 bytes), K (1024 bytes), m (1,000,000 bytes), or M (1,048,576 bytes).
-D
Report summary statistics about disk activity.
For detailed information about the output provided by each output mode, see the man page: 
$ man vmstat