When running critical applications on Linux servers, process crashes can cause significant downtime. Unlike Windows systems that have services managers, Linux requires more hands-on approaches for process supervision.

Linux offers several built-in mechanisms for process monitoring:

1. systemd Service Management:

[Unit]
Description=My Critical Application
After=network.target

[Service]
Type=simple
ExecStart=/path/to/your/application
Restart=always
RestartSec=5s

[Install]
WantedBy=multi-user.target

This configuration automatically restarts the application if it exits for any reason, with a 5-second delay between restart attempts.

2. Supervisor Daemon (supervisord):

[program:myapp]
command=/path/to/your/application
autostart=true
autorestart=true
startretries=3
startsecs=10

For more control, consider a bash monitoring script:

#!/bin/bash

APP_PATH="/path/to/your/application"
LOG_FILE="/var/log/app_monitor.log"

while true; do
    if ! pgrep -x "$(basename $APP_PATH)" > /dev/null; then
        echo "$(date): Application not running. Restarting..." >> $LOG_FILE
        $APP_PATH &
    fi
    sleep 10
done

For containerized applications, Docker provides built-in restart policies:

docker run -d --restart unless-stopped your_image

For production environments, consider dedicated process managers:

• PM2 (for Node.js applications)
• Runit
• Monit (with comprehensive monitoring capabilities)

When implementing process monitoring:

1. Set appropriate restart limits to prevent thrashing
2. Configure proper logging for crash analysis
3. Consider resource constraints (memory, CPU)
4. Implement proper signal handling in your application

In production environments, critical processes must remain available even after unexpected failures. While Linux processes can terminate for various reasons (segfaults, OOM kills, manual termination), we need reliable mechanisms to restart them automatically.

Linux offers several native approaches for process supervision:

Systemd Service Units

The most modern solution for most distributions (RHEL 7+, Ubuntu 15.04+). Example unit file at /etc/systemd/system/myapp.service:

[Unit]
Description=My Critical Application

[Service]
ExecStart=/usr/local/bin/myapp
Restart=always
RestartSec=5s

[Install]
WantedBy=multi-user.target

Key parameters:
- Restart=always: Restarts regardless of exit code
- RestartSec: Delay between restart attempts

Supervisor Daemons

For older systems without systemd, consider these alternatives:

# Using inittab (SysV init)
myapp:2345:respawn:/usr/local/bin/myapp

For more sophisticated monitoring (process + resource checks):

# /etc/monitrc
check process myapp matching "myapp"
    start program = "/usr/local/bin/myapp"
    stop program = "/usr/bin/pkill myapp"
    if failed port 8080 protocol http then restart
    if cpu > 80% for 5 cycles then alert
    if 5 restarts within 5 cycles then timeout

For Docker deployments, use restart policies:

docker run --restart unless-stopped -d myapp-image

Kubernetes provides even more robust options through pod restart policies and liveness probes.

When you need custom logic, a simple bash watchdog works:

#!/bin/bash
while true; do
    /usr/local/bin/myapp || {
        echo "Process crashed with status $?. Restarting..." >&2
        sleep 5
    }
done

Consider these factors when selecting a solution:
- System architecture (legacy vs modern)
- Required monitoring granularity
- Infrastructure constraints
- Available operational expertise