Which tool is most suitable for performing live collection of system information from a powered-on server?

The most suitable tool for performing live collection of system information from a powered-on server is vmstat. This tool is designed to monitor system performance by providing a variety of real-time statistics related to system processes, memory, paging, block I/O, traps, and CPU activity.

Using vmstat, system administrators can gain insight into the overall performance and resource utilization of the server while it is actively running. This includes data about how much system memory is free and how much is being used, as well as the CPU's loading and how processes are being scheduled. It is particularly useful for troubleshooting performance issues and understanding system behavior in live scenarios.

On the other hand, strings and hexdump are tools that are primarily used for examining and analyzing file contents rather than for live monitoring. Strings extracts human-readable text from binary files, and hexdump outputs binary data in a hexadecimal format, neither of which provides dynamic system performance metrics. Foremost is a tool used for file recovery, specifically aimed at recovering files based on file signatures, but it does not collect real-time system information.

Thus, vmstat stands out as the most effective choice for real-time system monitoring on a powered-on server.