When monitoring Ruby processes with top, developers often need to see full command-line arguments for debugging and process identification. Here's what's happening in your case:

• Expected behavior: top shows complete rake commands like rake db:migrate
• Current behavior: Only displays rake without arguments
• Environment: Ubuntu (newer version), RVM with Ruby Enterprise Edition

The top command reads process information from /proc/[pid]/cmdline. When arguments are truncated, it's usually due to:

// Typical /proc/[pid]/cmdline content for Ruby
ruby\u0000/path/to/rake\u0000db:migrate\u0000

1. Process Name Truncation Settings

Check if top is configured to show full command lines:

# Press 'c' while top is running to toggle command display
# Or start top with:
top -c

2. Ruby/RVM Process Wrapping

Some Ruby versions modify how command arguments are presented to the OS:

# Check how Ruby presents the process
ps -ef | grep rake
ps -auxww | grep rake  # Show wide output

3. Kernel Process Accounting Settings

Ubuntu's newer versions may limit process information visibility:

# Check kernel parameters
sysctl kernel.randomize_va_space
sysctl kernel.yama.ptrace_scope

# Temporary fix (as root):
echo 0 > /proc/sys/kernel/yama/ptrace_scope

Comparing Process Information Across Systems

# On working system:
cat /proc/$(pgrep -f "rake db:migrate")/cmdline | tr '\0' ' '

# On problematic system:
cat /proc/$(pgrep -f rake)/cmdline | tr '\0' ' '

Alternative Monitoring Tools

When top fails, try these alternatives:

# Show full command lines:
htop
ps auxww
pgrep -a rake

# More detailed process info:
cat /proc/[pid]/status
cat /proc/[pid]/environ

For Ubuntu systems, create a sysctl configuration file:

# /etc/sysctl.d/99-show-process-args.conf
kernel.yama.ptrace_scope = 0
kernel.randomize_va_space = 0

Then apply with:

sudo sysctl -p /etc/sysctl.d/99-show-process-args.conf

If system changes aren't possible, modify the Rake task:

# lib/tasks/debug.rake
task :set_proc_title do
  $0 = "rake #{ARGV.join(' ')}" # Set process title
end

# Then run:
rake set_proc_title db:migrate

---

When monitoring Ruby processes with top, developers often encounter cases where rake task arguments mysteriously disappear from the command column. This behavior varies across different Linux distributions and Ruby environments.

The top command reads process information from /proc/[pid]/cmdline, but what gets displayed depends on several factors:

1. Kernel parameters affecting process visibility
2. Ruby runtime configuration
3. Terminal width settings
4. Top's display mode configuration

First verify what the system actually sees by checking the raw process information:

cat /proc/$(pgrep -f rake)/cmdline | tr '\0' ' '

If this shows the full command but top doesn't, we're dealing with a display issue rather than an execution issue.

In top, press c to toggle command line display between truncated and full mode. For permanent setting:

echo "alias top='top -c'" >> ~/.bashrc
source ~/.bashrc

Some newer Linux kernels hide process arguments by default for security. Check and modify:

sysctl kernel.yama.ptrace_scope
sudo sysctl -w kernel.yama.ptrace_scope=0

When top proves unreliable, consider these alternatives:

# Using htop (more verbose by default)
sudo apt install htop
htop

# Using ps with custom format
ps auxww | grep rake

# Using pgrep with full output
pgrep -fa rake

For RVM/rbenv users, ensure proper process naming by setting:

export RUBY_GC_HEAP_INIT_SLOTS=600000
export RUBY_HEAP_SLOTS_INCREMENT=250000
export RUBY_HEAP_SLOTS_GROWTH_FACTOR=1

For servers where you always want full process visibility, create /etc/sysctl.d/10-ptrace.conf:

kernel.yama.ptrace_scope = 0
kernel.perf_event_paranoid = -1

Then apply with sudo sysctl -p /etc/sysctl.d/10-ptrace.conf

Be aware that showing full command lines may expose sensitive information. In production environments, consider:

• Using process monitoring tools that support argument sanitization
• Implementing centralized logging with access controls
• Using environment variables instead of command-line arguments for sensitive data