# A Beginner guide for "iotop" to processes on your Hard Disks

### What is iotop ?

while we are studying about the iotop It become important to understand what is it right ?

so iotop is a command line utility to monitor and check the usage of I/O operations of our disk. You can check official repository or [iotop](https://github.com/Tomas-M/iotop). it was written by Guillaume Chazarain.

iotop watches I/O usage information output by the Linux kernel (requires 2.6.20 or later) and displays a table of current I/O usage by processes or threads on the system.

It displays columns for the I/O bandwidth read and written by each process/thread during the sampling period. It also displays the % of time the thread/process spent while swapping in and while waiting on I/O. For each process, its I/O priority (class/level) is shown.

In addition, the total I/O bandwidth read and written during the sampling period is displayed at the top of the interface.

You can use the left and right arrows to change the sorting, r to reverse the sorting order, o to toggle the --only option, p to toggle the --processes option, a to toggle the --accumulated option, q to quit or i to change the priority of a thread or a process' thread(s). Any other key will force a refresh.

without making any delay let's move on the installation of this wonderful tool.

### installation of iotop

So, the installation of the iotop is so simple we don't have to do anything instead firing up a single command according to respective package manager and Linux Distro.

### Ubuntu/Debian/Linux Mint:

```bash
sudo apt install iotop
# while you've logged in with root user
apt isntall iotop
```

**CentOS/RHEL:**

```bash
sudo yum install iotop
# or
yum install iotop
```

### Basic Usage of iotop

Using iotop is not much hard until you understand the basics of disk i/o operations. However it is so simple to run it. Just type the below command and you are good to go for exploring the wonderland.

```bash
sudo iotop
```

This will display a list of processes along with their disk I/O statistics. The default output includes several important columns which you can see in the image:

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724687841673/a720c88c-245d-4a0a-b3a7-9b972ec61019.png align="center")

* **PID**: The Process ID.
    
* **PRIO**: The I/O priority of the process.
    
* **USER**: The user who owns the process.
    
* **DISK READ**: The amount of data read from the disk in KiB/s.
    
* **DISK WRITE**: The amount of data written to the disk in KiB/s.
    
* **SWAPIN**: The percentage of the process's I/O that is being swapped in.
    
* **IO**: The percentage of time the process is waiting on I/O.
    

You can navigate within `iotop` using simple commands:

* Press **<mark>o</mark>** to filter and display only processes with active I/O.
    
* Press `q` to quit the program.
    

### Advanced iotop Usage

**1\. Filtering by User or Process:** You can focus on specific users or processes using `iotop`. For instance, to filter by user, use:

```bash
sudo iotop -u username
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724688365914/e81c1c91-523a-47ca-9780-729d9d89efb9.png align="center")

Or to monitor a specific process:

```bash
sudo iotop -p PID
# below is my PID 3372 
sudo iotop -p 3372
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724688634037/1c71a82e-2370-48cd-ac72-4e9064c4cf22.png align="center")

**2\. Batch Mode for Logging:** Running `iotop` in batch mode allows you to log disk I/O activity for later analysis. This is particularly useful for long-term monitoring or troubleshooting:

```bash
sudo iotop -b -o > iotop.log
```

**3\. Customising Output:** Adjust the delay between updates using `-d`:

```bash
sudo iotop -d 5
```

Also you can limit the number of iterations with `-n`:

```bash
sudo iotop -n 10
```

Display values in kilobytes instead of the default megabytes with `-k`:

```bash
sudo iotop -k
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724688783077/bb552c7a-e0c8-42d5-9692-6c497f82803b.png align="center")

To suppress some lines of header. this will suppress the lines of header.

```bash
sudo iotop -q
# This will now suppress some line of header in the output.
```

![](https://cdn.hashnode.com/res/hashnode/image/upload/v1724688928923/07d19875-bdfb-45e3-9437-73737eb22dbe.png align="center")

**4\. Combining with Other Tools:** For a more automated approach, you can combine `iotop` with `cron` to run at regular intervals, or use `grep` to filter the output for specific patterns:

```bash
sudo iotop -b -o | grep 'pattern' > filtered_iotop.log
```

### Optimizing Disk Performance Using iotop

**1\. Identifying and Terminating Problematic Processes:** If `iotop` reveals a process that’s consuming too much I/O, you can terminate it to free up resources:

```bash
sudo kill -9 PID
```

**2\. Adjusting I/O Priorities:** For processes that need to run but are consuming too much I/O, you can adjust their I/O priority using `ionice`:

```bash
sudo ionice -c3 -p PID
```

This command will set the process to the "idle" priority class, meaning it will only use disk I/O when the system is otherwise idle.

**3\. Proactive Monitoring:** Set up alerts based on `iotop` output to catch I/O issues early. For example, you can use a monitoring script that sends an email or triggers an alert if disk I/O crosses a certain threshold.

**4\. Regular Analysis:** Make it a habit to run `iotop` periodically, especially if you notice performance issues. Regular monitoring helps you catch problems early, ensuring your system runs smoothly.

### Use Cases of iotop

Below are some use cases that you can consider for using iotop which can be helpful in a lot ways.

**1\. Identifying Disk I/O Bottlenecks:** High disk I/O can cause significant slowdowns in system performance. With `iotop`, you can quickly identify which processes are consuming the most I/O resources. For example, if your system is sluggish, running `iotop` can help you pinpoint processes that are hogging the disk, allowing you to take appropriate action.

**2\. Monitoring Performance of Disk-Intensive Applications:** Applications like databases, backup processes, or large file transfers are always very disk-intensive. Using `iotop`, you can monitor these applications in real-time, ensuring they aren’t causing unnecessary strain on your system or interfering with other processes.

**3\. Diagnosing Swap Usage Issues:** If your system is heavily using swap, it can lead to increased disk I/O, slowing down your system. `iotop` helps you monitor swap usage as well and identify processes that are causing excessive swapping and enabling you to optimise memory usage and reduce swap dependence.

**4\. Analysing Disk Write Patterns:** Understanding which processes are writing heavily to disk can help in managing disk wear, especially for SSDs. `iotop` provides a clear view of disk write activity, making it easier to manage disk health and longevity.

I hope you've enjoyed this article on iotop, you can also use some resources mentioned below to expand your understanding on iotop.

* [https://linux.die.net/man/1/iotop](https://linux.die.net/man/1/iotop)
    
* [https://github.com/Tomas-M/iotop](https://github.com/Tomas-M/iotop)