rkt-gc.rb

#!/usr/bin/env ruby

# Wraps 'rkt gc' to handle when rkt cannot successfully remove an old pod
# because it is still mounted in some processes' namespace. To use, pass
# options you would normally pass to 'rkt gc':
# Example: sudo ./rkt-gc.rb --grace-period=0s

require 'open3'

def with_error_handling
  yield
rescue Errno::ENOENT, Errno::EINVAL => e
  []
end

def run_command(cmd, show_stdout = false)
  result = {}
  result[:stdout], result[:stderr], result[:status] = Open3.capture3(cmd)

  puts result[:stdout] if show_stdout

  unless result[:status].success?
    puts result[:stderr]
    exit(result[:status].exitstatus)
  end
  result
end

raw_gc = run_command("/usr/bin/rkt gc #{ARGV.join(' ')}", true)

busy_mount_points = []
raw_gc[:stderr].lines.each do |line|
  if line =~ /device or resource busy$/
    busy_mount_points << line.split.grep(/exited-garbage/).first.chomp(':')
  end
end

if busy_mount_points.size > 0
  Dir.glob('/proc/*/mountinfo').each do |m|
    lines = with_error_handling do
      File.open(m, 'r') do |f|
        f.readlines
      end
    end
    busy_mount_points.each do |mount_point|
      results = lines.grep(/#{mount_point}/)
      if results.size > 0
        pid = m.strip.split('/')[2]
        run_command("/usr/bin/nsenter -m -p -t #{pid} umount --recursive #{mount_point}")
      end
    end
  end

  # All mounts are now unmounted, so rerun rkt gc
  run_command("/usr/bin/rkt gc #{ARGV.join(' ')}")
end