Managing Tasks in CentOS 7

The task management tool in CentOS 7 is GNOME System Monitor.

Accessing System Monitor

• Access it from the desktop:

  • Go to Applications > System Tools > System Monitor.

• Alternatively, access it via terminal:

  • Command: gnome-system-monitor

System Monitor Tabs

1. Processes Tab

   • Displays all running processes on the computer, indicating how each process utilizes system resources.

   • Sort information by column by clicking the column name (toggle between ascending and descending).

   • End Process Button: Highlight a process and click this button to stop it safely.

   • Right-click options: Right-click a process to select End or Kill, which allows for more aggressive termination of tasks when necessary.

   • View Menu: Control process display with options such as All Processes, My Processes, Active Processes for better management.

   • Parent processes marked with a diamond symbol next to process names, indicating their hierarchical relationship when the Dependency option is selected.

2. Resources Tab

   • Shows usage history of CPU, memory, swap memory, and network in graphical format for easy visualization.

   • Command equivalent: free (more details covered later), which provides an overview of memory usage, including total, used, free, and cached memory status.

3. File Systems Tab

   • Displays information about mounted file systems and their types, helping users understand disk allocations.

   • Shows disk space utilization: total used and free space, aiding in storage management.

   • Columns can be sorted alphabetically or numerically to locate specific drives or partitions easily.

Commands for Task Management

ps command

• The ps command lists running system processes and their resource usage effectively.

• Syntax: ps [options]

  • Shows user ownership of processes, which is vital for administration tasks.

  • Displays Process ID (PID) assigned by kernel(the core of and operating system), essential for process management.

Common ps Options:

kill Command

• The kill command is used to terminate processes, which is crucial for managing unresponsive applications.

• Basic Syntax: kill [option] PID

  • Sends signals to specified processes with various impacts, allowing for graceful or forced termination.

Common Uses:

• To stop a specific process:

  kill PID

• Use -9 for stronger termination:

  kill -9 PID

• SIGHUP: Cleans up processes effectively; this is cleaner than -9 signal:

  kill -SIGHUP PID

Important Notes

• Be cautious when using kill with PIDs as it can terminate parent processes and all child processes spawned by it (e.g., killing gnome-session will log the user out).

• To view processes associated with a user:
  ```bash
  ps -ef | grep User01 | more -d20