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Linux Academy by Uirá Ribeiro

Modify the Execution Priority of Processes in Linux

It is possible to modify the execution priority of processes on Linux using the nice and renice commands. These commands are extremely useful in multi-user environments

Imagine a server with many users logged in and each one running something. In this type of environment, it is necessary to give more or less processing slices to the various user programs to maintain a stable and organized environment.

Nice command

Use:

$ nice [-n prioritization_setting] [command]

The nice command adjusts a process’s available CPU time to higher or lower priority.

In English the word “nice” means “cool”. If the adjustment of The priority for a process is a positive number, meaning that it is being cooler with the other programs decreasing their priority.

If the adjustment is a negative number, it means that the program is being less cool, increasing your execution priority and leaving less CPU time for the other programs.

The possible priority adjustment ranges from —20 (highest priority/least cool) to 19 (coolest, least priority).

If no adjustment value is passed, the nice command will adjust the priority to +10, reducing the process execution time.

$ nice updatedb &

In this example, the updatedb command has lower execution priority.

$ nice —n —10 payroll

In this example the command Payroll will be executed with higher priority.

Renice Command

Use:

$ renice [+/-] setting_priority [options] PID/user

The renice command adjusts the execution priority of processes that are already running. By default, the renice command takes the PID of a particular process as a parameter.

The priority setting is an integer ranging from —20 (highest priority) to +20 (execute anything before this process).

The most common options are:

  • -p: Get a PID to change its priority.
  • -u: Receives a username to change the priority of all processes running on this user.
  • -g: Receives a name from a group to change the priority of all processes belonging to this group.

Example:

# renice -1 987 -u daemon root -p 32

In this example, the process number PID 987, PID 32, and all processes that daemon and root users own will have higher priority.

See how to work with processes in Linux and put processes in the background.

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