iostat(1)
Name
iostat − report I/O statistics
Syntax
iostat [ −c ] [ −t ] [ disknames ] [ interval ] [ count ]
Description
The iostat command reports I/O statistics for terminals, disks and cpus. For terminals the number of input and output characters are counted. For disks the number of 512 byte blocks per second and number of transfers per second are displayed. For cpus, it provides the percentage of time the system has spent in user mode, in user mode running low priority (niced) processes, in system mode, and idling. On multiprocessor systems these cpu statistics represent a cumulative summary of all the cpus.
The optional disknames argument causes disk statistics to be displayed for the specified disks. If this argument is not specified then disk statistics will be displayed for the first 3 disks only.
The optional interval argument causes iostat to report once each interval seconds. The first report is for all time since a reboot and each subsequent report is for the last interval only.
The optional count argument restricts the number of reports.
Options
−cDisplays the percentage of time each cpu spent in user mode, running low priority (nice’d) processes, in system mode, and idling.
−tDisplays the number of characters read from and written to terminals.
Examples
This example will cause cpu and disk statistics for the 5 disks ra0, ra1, ra2, ra3, and ra4.
iostat ra0 ra1 ra2 ra3 ra4
This example will cause cpu, terminal, and disk statistics for ra0 to be displayed and updated every 2 seconds.
iostat -t ra0 2
Files
/dev/kmem
/vmunix