The renice command is used to change the priority of a running process by specifying its PID and the new nice value. The -n flag indicates the amount of change in the nice value, which can be positive or negative. A lower nice value means a higher priority, so -15 will increase the priority of the process with PID 2274. The administrator needs to have root privileges to do this.
References:
* The renice command is listed as one of the commands to manipulate process priority in the web search result 1.
* The renice command is also explained with examples in the web search result 2.
* The CompTIA Linux+ Certification Exam Objectives mention that the candidate should be able to
"manage process execution priorities" as part of the System Operation and Maintenance domain1.