Cheatsheet & Examples: iostat
iostat is a command-line tool used to monitor system input/output (I/O) statistics, including CPU utilization and disk activity. It provides insights into disk read/write speeds, I/O queue lengths, and device performance.
Display Overall System I/O Statistics
Example Usage:
iostat
What it does: Shows a summary of CPU and disk I/O statistics for the entire system. The output includes average values over the time since the last boot.
Command-line Arguments Explained:
- None: The command runs with default options, displaying system-wide I/O data.
Monitor I/O Statistics at Intervals
Example Usage:
iostat 1 5
What it does: Displays I/O statistics at 1-second intervals for 5 iterations, allowing real-time observation of disk and CPU activity.
Command-line Arguments Explained:
1: Interval in seconds between updates.5: Number of iterations (updates) to display.
Show Disk I/O Statistics Only
Example Usage:
iostat -d
What it does: Focuses on disk I/O statistics, omitting CPU utilization details.
Command-line Arguments Explained:
-d: Disables CPU statistics and shows only disk-related data.
Display Extended Disk I/O Statistics
Example Usage:
iostat -x
What it does: Provides detailed disk I/O statistics, such as average request size, I/O wait time, and service time.
Command-line Arguments Explained:
-x: Enables extended statistics for disks, offering more in-depth metrics.
Monitor Specific Disks or Devices
Example Usage:
iostat -d sda sdb
What it does:
Displays I/O statistics for the specified disks (sda, sdb) instead of all devices.
Command-line Arguments Explained:
-d: Shows disk statistics.sda sdb: Specifies one or more disk device names (e.g.,sda,sdb).
Use Custom Units for I/O Metrics
Example Usage:
iostat -m 2
What it does: Displays I/O statistics in megabytes (MB) instead of kilobytes (KB) or bytes, with updates every 2 seconds.
Command-line Arguments Explained:
-m: Display I/O statistics in megabytes (MB) rather than kilobytes (KB).2: Interval in seconds between updates.
Include Timestamps in Output
Example Usage:
iostat -t 1
What it does: Displays I/O statistics at 1-second intervals, with timestamps added to each output line.
Command-line Arguments Explained:
-t: Displays timestamps for each I/O statistics update.
Show Device Names Instead of Major/Minor Numbers
Example Usage:
iostat -N
What it does: Replaces device major/minor numbers with human-readable device names in the output.
Command-line Arguments Explained:
-N: Displays device names (e.g.,/dev/sda) instead of numerical identifiers.
Monitor CPU Utilization Only
Example Usage:
iostat -c
What it does: Focuses on CPU utilization statistics, omitting disk I/O details.
Command-line Arguments Explained:
-c: Displays CPU utilization statistics instead of disk I/O data.
Show Per-Partition Disk I/O Statistics
Example Usage:
iostat -d -p 1
What it does:
Reveals I/O statistics for individual disk partitions (e.g., sda1, sda2) at 1-second intervals.
Command-line Arguments Explained:
-d: Shows disk statistics.-p: Displays I/O statistics for each partition of the disk.
