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VONDS ©

Lab 44: Process Management

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Control responsiveness by moving jobs between the foreground and background, then reduce CPU impact with nice. Validate job state and apply priority changes without disrupting interactive work.

troubleshooting core services

Scenario

The server feels sluggish during routine work, and you suspect a mix of interactive shells and CPU-heavy commands are competing for resources. You need to manage job state (foreground versus background) and reduce the priority of a noisy workload so the system stays usable while it runs.

Operator context

Job control keeps you productive in a live shell session. Priority control helps you reduce impact on shared systems without killing work that still needs to finish.

Objective

  • Launch a long-running job in the background and confirm it is running.
  • Bring a background job to the foreground and suspend it safely.
  • Resume a suspended job in the background and confirm job state.
  • Start a CPU-heavy workload with reduced priority using nice.

Concepts

  • Job control is scoped to the current shell and tracks jobs started from that session.
  • Foreground jobs are attached to your terminal; background jobs continue running while you keep working.
  • Suspending a job stops it without terminating, so it can be resumed later.
  • Nice values influence CPU scheduling: higher nice values generally reduce CPU priority for that process.

Walkthrough

Step 1 : Launch a long-running job in the background.
Command 
sleep 60 &

Appending & starts the command in the background and returns you to the prompt. This is useful for work that does not require interactive input. 

[1] 1234
Step 2 : Confirm the job is tracked by the current shell.
Command 
jobs

jobs reports tasks the current shell is tracking. This is job control scope, not a full system process list. 

[1]+  Running                 sleep 60 &
Step 3 : Bring the job to the foreground and suspend it.
Command 
fg %1

fg attaches the job to your terminal again. To pause it without killing it, press Ctrl+Z to stop the job and return control to your shell. 

sleep 60

[Ctrl+Z]
[1]+  Stopped                 sleep 60
Step 4 : Resume the job in the background.
Command 
bg %1

bg continues a stopped job but keeps it in the background. This is a clean way to let work finish while you keep using the terminal. 

[1]+ sleep 60 &
Step 5 : Launch a CPU-heavy task with reduced priority.
Safety note

yes generates endless output. Redirect to /dev/null as shown, and treat this as a test workload you should stop after confirming behavior.

Command 
nice -n 10 yes > /dev/null &

nice starts a process with an adjusted scheduling priority. Higher nice values generally reduce CPU priority so interactive tasks remain responsive. 

[2] 1245

Common breakpoints

jobs output is empty

Job control only tracks processes started from the current shell. If the job was started in a different terminal or session, it will not appear here.

fg fails: “no such job”

The job ID is shell-scoped. Re-run jobs and use the correct job spec (for example %1).

Ctrl+Z does not suspend the command

Some programs handle signals differently, and some may ignore the terminal stop signal. Use the shell’s job list to confirm state and test with a simple workload first.

System still feels slow after nice

Nice affects CPU scheduling priority, not I/O or memory pressure. If the slowdown is from disk or memory, you need a different mitigation than nice alone.

Cleanup checklist

Stop any test workloads you started so they do not continue consuming CPU after you finish the lab.

Commands 
jobs
kill %1
kill %2
Success signal

jobs returns no active jobs, and the terminal remains responsive with no leftover test processes running.

Reference

  • sleep 60 & : Runs a command in the background and returns control to the shell.
    • &: backgrounds the command.
  • jobs : Lists jobs managed by the current shell session.
  • fg %<job> : Brings a job to the foreground.
    • %<job>: job specifier from jobs (for example %1).
  • bg %<job> : Resumes a stopped job in the background.
    • %<job>: job specifier from jobs (for example %1).
  • nice -n <value> <command> : Starts a command with adjusted scheduling priority.
    • -n <value>: sets the nice value.
  • yes > /dev/null : Generates continuous output redirected to null, commonly used as a simple CPU load test.
    • > /dev/null: discards output.
  • kill %<job> : Terminates a job tracked by the current shell.
    • %<job>: job specifier from jobs (for example %2).