What does the 'nice' command primarily adjust?

The 'nice' command primarily adjusts process priority in a Linux environment. When you run a command with 'nice', it allows you to set the niceness level of a process, which determines how much CPU time the process receives in relation to other processes. A lower niceness value means a higher priority for the process, allowing it to use more CPU time, while a higher niceness value indicates a lower priority, which can be advantageous in managing system resources when multiple processes are running.

This command is particularly useful in situations where you want to ensure that critical processes are allocated more CPU resources without needing to stop or kill other running processes. By adjusting the niceness value, users can effectively manage the workload on the system, allowing for smoother multitasking and response times.

The other options, such as user permissions, file ownership, and system time adjustments, are managed through different commands and mechanisms in Linux. The 'nice' command specifically focuses on the allocation of CPU resources to running processes based on priority, which is why it is the correct answer.