Process Management

Understanding Linux Processes

Process Basics

Process ID (PID)
Parent Process ID (PPID)
Process States
Process Priority
Resource Usage

Process States

Running (R)
Sleeping (S)
Uninterruptible Sleep (D)
Stopped (T)
Zombie (Z)

Process Monitoring

Basic Process Commands

ps aux              # List all processes
top                 # Interactive process viewer
htop                # Enhanced process viewer
pgrep pattern       # Find processes by pattern

Process Information

ps -f pid           # Detailed process info
ps -u username      # User processes
ps -C command       # Find by command name
lsof                # List open files

Job Control

Foreground and Background

command &           # Start in background
Ctrl+Z              # Suspend process
bg                  # Resume in background
fg                  # Bring to foreground
jobs                # List jobs

Process Control

kill pid            # Send SIGTERM
kill -9 pid         # Force kill (SIGKILL)
killall process     # Kill by name
pkill pattern       # Kill by pattern

Process Scheduling

Nice and Renice

nice -n value command    # Start with priority
renice value -p pid      # Change priority

Cron Jobs

crontab -e              # Edit cron jobs
crontab -l              # List cron jobs
# Format: min hour day month weekday command

At Jobs

at now + 1 hour         # Schedule one-time job
atq                     # List pending jobs
atrm job_number         # Remove scheduled job

System Monitoring

Resource Usage

free -h                # Memory usage
uptime                # System load
vmstat                # Virtual memory stats
iostat                # I/O statistics

Performance Monitoring

sysstat               # System statistics
sar                   # System activity report
dstat                 # System resource stats

Hands-on Practice

Exercise 1: Process Management

Start a process: sleep 1000 &
List processes: ps aux | grep sleep
Change priority: renice +5 -p PID
Terminate process: kill PID

Exercise 2: Job Scheduling

Create cron job: crontab -e
Add daily backup: 0 0 * * * /backup.sh
List scheduled jobs: crontab -l

Process Troubleshooting

Common Issues

High CPU usage
Memory leaks
Zombie processes
Hung processes

Debugging Tools

strace               # Trace system calls
ltrace               # Library call tracer
gdb                  # GNU debugger
valgrind             # Memory debugger

Additional Resources

Next Steps

Learn advanced process management
Master system monitoring tools
Understand process priorities
Explore process debugging