Linux ionice: set I/O priority for command


In Linux, when operating with root administrator privileges, you have the ability to adjust the I/O priority of processes. This is particularly useful when you need to manage system resources more effectively. The tool for this task is the `ionice` command.

Here’s how you can utilize `ionice`:

  1. Running a Command with Highest I/O Priority:

    To execute a command with the highest I/O priority, use the following syntax:

       ionice -c1 -n0 /bin/some-command

    In this example, `-c1` sets the class to ‘real time’, and `-n0` assigns the highest priority within that class.

  2. Applying to an Existing Process:

    Alternatively, if you want to set the I/O priority for an already running process, use its Process ID (PID):

       ionice -c1 -n0 -p PID

    You can find the PID of a process using commands like `ps`, `top`, or `htop`. These tools provide a snapshot of current processes and their respective PIDs.

  3. Setting Lowest I/O Priority:

    To assign the lowest I/O priority to a process or command, you would adjust the parameters to `-c3 -n7`. For example:

       ionice -c3 -n7 /bin/some-command

    Here, `-c3` places the process in the ‘Idle’ class, ensuring it only uses I/O when no other process needs it, while `-n7` is the lowest priority within this class.

Understanding and manipulating process priorities can be crucial for optimal system performance, especially on servers or in environments where resource allocation is key. Remember, modifying I/O priorities should be done with care, as it can significantly affect system performance and behavior.