How to Reduce CPU Impact of an Already Running Backup Process?
Short answer
A renice -n 15 -p
Question
Key Takeaways
The exam tests both the difference between nice and renice and the meaning of positive nice values: positive values lower priority, and renice is required for an already-running process.
Learn how to use renice with a positive nice value to lower the CPU priority of an already-running backup process on Linux, minimizing its impact on other services. This XK0-005 exam prep explains the difference between nice and renice and the correct syntax.
Common mistake: Choosing option B is a common mistake because it uses the correct nice value (15) but the wrong command: nice starts a new process and does not accept -p, while the backup is already running and needs renice.
Expert Analysis
Why the Answer Is Correct
A is correct because renice -n 15 -p changes the nice value of an existing process to 15, lowering its scheduling priority. On Linux, nice values range from -20 (highest priority) to 19 (lowest); a positive value makes the process "nicer" to others, so the backup still runs but consumes less CPU. Since the backup is already running, renice is the appropriate command.
Why the Other Options Are Wrong
Option B is wrong because nice -n 15 -p is invalid: nice is used to start a new command with a given priority and does not support a -p option to target a PID, nor can it change an already-running process. Option C uses -15, which would raise the backup's priority, increasing CPU contention with other services. Option D also uses -15, and nice cannot be used on a running process.
Community Comment Notes
Commenters correctly identified that positive nice values lower priority, as noted in comment 1: -20 is highest, 19 is lowest, and setting 15 would allow the backup to continue while freeing CPU. Comment 2 confirms the range and behavior of nice priorities. Comment 3 suggests renice -n -15 -p, but that would actually increase the backup’s priority; the correct approach for reducing impact is a positive value like 15.
Official Reference
- https://man7.org/linux/man-pages/man1/renice.1.html
- https://man7.org/linux/man-pages/man1/nice.1.html
- https://www.gnu.org/software/coreutils/manual/html_node/nice-invocation.html
These links open the official vendor documentation in a new tab.
Exam Strategy
Remember the mnemonic 'renice is for running, nice is for new' and that positive nice values are 'nice' to other processes (lower priority). When asked about an already-started process, immediately choose renice with a positive number.
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 3 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 3
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BlackSkullz 👍 3 Answered AI'm going with A. The nice priorites go from -20 to 19, with -20 being the highest priority and 19 being the lowest priority. Since the process must run, setting the priority to 15 would lower the priority of the process while ensuring that the process is still running and CPU time can be freed up for the users and services on the system. B would set it's priority to -15 which wouldn't solve anything because it would give it the 6th highest priority setting and make it consume even more resources
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bongobo 👍 11 to 20 Runs the specified processes slower than the base priority. 0 Sets priority of the specified processes to the base scheduling priority. -20 to -1 Runs the specified processes quicker than the base priority.
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mirrblvck 👍 2c renice -n -15 -p
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