Fly SSH Console Usage

Critical Considerations

1. Machine Must Be Running

Fly.io machines may be stopped. Before using

fly ssh console

, ensure a machine is running:

Option A: Start machine explicitly

# List machines to find IDs
fly machines list -a smooth-nav

# Start a specific machine
fly machine start <machine-id> -a smooth-nav

Option B: Wake machine with HTTP request

# Fetch a page to auto-start the machine
curl -I https://smooth-nav.fly.dev/

2. No Shell - Direct Command Execution Only

fly ssh console

executes commands directly, not through a shell. This means:

❌ Don't use:

• Pipes:

  ps aux | grep puma

• Redirection:

  echo "test" > file.txt

• Shell operators:

  &&

  ,

  ||

  ,

  ;

• Shell expansions:

  *.txt

  ,

  ~

  ,

  $HOME

✅ Do use:

• Direct commands:

  ps auxww

• Multiple separate

  fly ssh console

  calls for complex operations
• Command-specific options instead of pipes

Example - Wrong vs Right:

# ❌ Wrong (pipe won't work)
fly ssh console -a smooth-nav -C "ps aux | grep puma"

# ✅ Right (use grep command directly)
fly ssh console -a smooth-nav -C "ps auxww" | grep puma

# Or use ps filtering
fly ssh console -a smooth-nav -C "ps -C puma -o pid,user,%mem,%cpu,command"

3. Debian Linux Commands (Not macOS)

The Fly.io machines run Debian Linux, which has different command options than macOS.

Common Differences

ps command:

# ❌ macOS syntax (doesn't work on Linux)
fly ssh console -a smooth-nav -C "ps auxww -o %mem"

# ✅ Debian Linux syntax
fly ssh console -a smooth-nav -C "ps auxww"
fly ssh console -a smooth-nav -C "ps -eo pid,user,%mem,%cpu,command"
fly ssh console -a smooth-nav -C "ps -C navigator -o pid,%mem,command"

Memory inspection:

# Show all processes with memory usage
fly ssh console -a smooth-nav -C "ps auxww"

# Show specific process
fly ssh console -a smooth-nav -C "ps -C navigator -o pid,user,%mem,vsz,rss,command"

# Show top memory consumers
fly ssh console -a smooth-nav -C "ps aux --sort=-%mem | head -20"

File operations:

# List files
fly ssh console -a smooth-nav -C "ls -lah /data/db"

# Read file
fly ssh console -a smooth-nav -C "cat /rails/config/navigator.yml"

# Check disk usage
fly ssh console -a smooth-nav -C "df -h"

Common Use Cases

Memory Usage Analysis

# Get comprehensive process list with memory
fly ssh console -a smooth-nav -C "ps auxww"

# Show only relevant processes (filter locally)
fly ssh console -a smooth-nav -C "ps auxww" | grep -E 'navigator|puma|redis'

# Check specific process memory
fly ssh console -a smooth-nav -C "ps -C navigator -o pid,user,%mem,vsz,rss,command"

Understanding ps memory columns:

• %MEM

  - Percentage of physical RAM used

• VSZ

  - Virtual memory size (KB)

• RSS

  - Resident Set Size (actual physical memory in KB)

Process Inspection

# List all running processes
fly ssh console -a smooth-nav -C "ps auxww"

# Check if specific process is running
fly ssh console -a smooth-nav -C "ps -C puma -o pid,command"

# Show process tree
fly ssh console -a smooth-nav -C "ps auxwwf"

# Count processes by name
fly ssh console -a smooth-nav -C "ps aux" | grep -c puma

File and Directory Inspection

# List databases
fly ssh console -a smooth-nav -C "ls -lh /data/db/*.sqlite3"

# Check configuration
fly ssh console -a smooth-nav -C "cat /rails/config/navigator.yml"

# Check logs (most recent lines)
fly ssh console -a smooth-nav -C "tail -100 /data/log/production.log"

# Check disk space
fly ssh console -a smooth-nav -C "df -h /data"

Network and Port Inspection

# Check listening ports
fly ssh console -a smooth-nav -C "netstat -tlnp"

# Check specific port
fly ssh console -a smooth-nav -C "netstat -tlnp" | grep 28080

Region-Specific Commands

# Specify region
fly ssh console -a smooth-nav -r iad -C "ps auxww"

# List available regions
fly regions list -a smooth-nav

Multi-Application Commands

# Compare smooth-nav (with optimizations)
fly ssh console -a smooth-nav -C "ps auxww" | grep -E 'navigator|puma|redis'

# Compare smooth (original)
fly ssh console -a smooth -C "ps auxww" | grep -E 'navigator|puma|redis'

Debugging Tips

Check if machine is accessible

# Ping the machine
fly ssh console -a smooth-nav -C "echo ok"

Check Navigator status

# Check if Navigator is running
fly ssh console -a smooth-nav -C "ps -C navigator -o pid,user,command"

# Check Navigator version
fly ssh console -a smooth-nav -C "navigator --version"

Check Rails processes

# Check Action Cable
fly ssh console -a smooth-nav -C "ps auxww" | grep "cable/config.ru"

# Check tenant Rails apps
fly ssh console -a smooth-nav -C "ps auxww" | grep "rails/config.ru"

Verify environment

# Check environment variables (for specific process)
fly ssh console -a smooth-nav -C "cat /proc/1/environ" | tr '\0' '\n'

Performance Considerations

• Each

  fly ssh console

  call incurs network latency
• For complex analysis, consider multiple separate calls rather than trying to use shell features
• Filter output locally (on your machine) rather than trying to filter remotely

Example Workflows

Analyze memory after deployment

# 1. Ensure machine is running
curl -I https://smooth-nav.fly.dev/

# 2. Wait a few seconds for cold start to complete
sleep 5

# 3. Get process list
fly ssh console -a smooth-nav -C "ps auxww" > /tmp/smooth-nav-ps.txt

# 4. Analyze locally
grep -E 'navigator|puma|redis' /tmp/smooth-nav-ps.txt

Compare memory usage across apps

# Get both process lists
fly ssh console -a smooth-nav -C "ps auxww" > /tmp/nav-ps.txt
fly ssh console -a smooth -C "ps auxww" > /tmp/smooth-ps.txt

# Compare
echo "=== smooth-nav ==="
grep -E 'navigator|puma|redis' /tmp/nav-ps.txt

echo "=== smooth ==="
grep -E 'navigator|puma|redis' /tmp/smooth-ps.txt

Check if Action Cable is running

# Quick check
fly ssh console -a smooth-nav -C "ps auxww" | grep -q "cable/config.ru" && echo "Action Cable running" || echo "Action Cable NOT running"

Common Errors and Solutions

Error: "no machines available"

Solution: Machine is stopped. Start it with

fly machine start

or trigger with HTTP request.

Error: "connection refused"

Solution: Machine might be starting. Wait 10-30 seconds and retry.

Error: "command not found"

Solution: Verify the command exists in Debian. Check available commands with:

fly ssh console -a smooth-nav -C "which <command>"

Pipe or redirection doesn't work

Solution: Don't use shell operators in

-C

argument. Filter/redirect on your local machine instead.