应如何配置 crashkernel 参数，以便在 RHEL6 上使用 kdump？

Issue

• 使 kdump 正常工作的正确 crashkernel 参数是什么？
• 当内核 panic 时出现错误 "crashkernel reservation failed - memory is in use"
• 在配置 crashkernel 参数时，kdump 服务要么无法启动，要么启动时显示此警告：

Your running kernel is using more than 70% of the amount of space you reserved for 
kdump, you should consider increasing your crashkernel reservation

• kdump 服务重启失败并显示以下错误

Please reserve memory by passing "crashkernel=X@Y" parameter to the kernel