149 lines
3.5 KiB
Markdown
149 lines
3.5 KiB
Markdown
# Process Monitoring and Management in Linux
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## 1. Viewing Running Processes
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Let's start with the basic commands to view running processes:
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### ps - Process Status
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The 'ps' command provides a snapshot of current processes.
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Basic usage:
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`ps
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Common options:
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- `-aux`: Shows all processes for all users
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- `-ef`: Similar to aux, but in a different format
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- `-lax`: Provides more detailed information
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### top - Table of Processes
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'top' provides a real-time, dynamic view of running processes.
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Basic usage:
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`top`
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In top, you can use:
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- 'q' to quit
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- 'k' to kill a process (you'll be prompted for the PID)
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- 'r' to renice (change priority) of a process
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### htop - Interactive Process Viewer
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'htop' is an improved version of 'top' with a more user-friendly interface.
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Install it (if not already installed):
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- `sudo apt install htop` # For Debian/Ubuntu
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- `sudo yum install htop` # For CentOS/RHEL
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Run it:
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`htop`
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## 2. Process Management
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### kill - Terminate a Process
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The 'kill' command sends a signal to a process, by default the TERM signal.
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Basic usage:
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`kill PID`
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Common signals:
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- SIGTERM (15): Graceful termination
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- SIGKILL (9): Forceful termination
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Example:
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`kill -9 1234`
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### killall - Kill Processes by Name
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'killall' allows you to kill all processes with a given name.
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Example:
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`killall firefox`
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### pkill - Kill Processes Based on Name and Other Attributes
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'pkill' is more flexible than killall, allowing you to kill processes based on various attributes.
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Example:
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`pkill -u username firefox`
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### nice and renice - Adjust Process Priority
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'nice' starts a process with a specified priority, while 'renice' changes the priority of a running process.
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Nice values range from -20 (highest priority) to 19 (lowest priority).
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Example:
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- `nice -n 10 command` # Start 'command' with lower priority
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- `renice -n 5 -p PID` # Change priority of running process
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## 3. Background and Foreground Processes
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### Start a process in the background:
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`command &`
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### Move a running process to the background:
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Press Ctrl+Z
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### Bring a background process to the foreground:
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`fg %job_number`
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### List background jobs:
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`jobs`
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## 4. Advanced Monitoring Tools
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### iotop - I/O Monitoring
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'iotop' shows I/O usage by processes.
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Install:
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- `sudo apt install iotop # For Debian/Ubuntu`
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- `sudo yum install iotop # For CentOS/RHEL`
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Run:
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`sudo iotop`
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### nethogs - Network Monitoring
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'nethogs' shows network usage by process.
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Install:
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- `sudo apt install nethogs` # For Debian/Ubuntu
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- `sudo yum install nethogs` # For CentOS/RHEL
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Run:
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`sudo nethogs`
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### lsof - List Open Files
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'lsof' lists open files and the processes using them.
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Example (list all network connections):
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`sudo lsof -i`
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## 5. System Monitoring
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### free - Display Amount of Free and Used Memory
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`free -h` # -h for human-readable format
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### vmstat - Report Virtual Memory Statistics
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`vmstat 1` # Report every second
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### iostat - Report CPU Statistics and I/O Statistics
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`iostat 1` # Report every second
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## 6. Process Tracking and Analysis
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### strace - Trace System Calls and Signals
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'strace' is useful for diagnosing problems with processes.
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Example:
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`strace command`
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### ltrace - Library Call Tracer
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'ltrace' is similar to strace but for library calls.
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Example:
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`ltrace command`
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## 7. Continuous Monitoring with watch
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The 'watch' command allows you to run any command periodically, showing output in fullscreen.
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Example (update process list every 2 seconds and look at top 5 lines of output):
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- `watch -n 2 'ps aux | sort -nrk 3,3 | head -n 5'`
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