The command fw ctl debug 0 is used to disable Check Point's kernel debugging functionality. When executed, it sets the size of the kernel debug buffer to zero, which deallocates the buffer and stops the collection of any new debug information. This action effectively clears any previously stored messages and ensures that no output from past or current debugging sessions is displayed, thus addressing the issue of seeing residual output from a previous debug.

A. fw ctl clean buffer = 0: This is not a valid Check Point command. The syntax is incorrect, and fw ctl clean is not a recognized command for managing the debug buffer.

C. fw ctl zdebug disable: This syntax is incorrect. The command to clear the debug buffer without disabling debugging is fw ctl zdebug, not fw ctl zdebug disable.

D. fw ctl debug = 0: This syntax is incorrect. The command does not use an equals sign (=) to assign the buffer size; the value is passed as a direct argument.

1. Check Point R80.40 CLI Reference Guide: In the chapter "Firewall and Kernel Commands," under the section for the fw command, the fw ctl debug subcommand is detailed. The guide explicitly states, "To turn off kernel debugging, run: [Expert@HostName:0]# fw ctl debug 0". This confirms that setting the debug level to 0 disables the feature.

2. Check Point Support Center, SK Article sk112334, "How to use the 'fw ctl zdebug' command": This official document clarifies the distinction between commands. It shows that fw ctl debug 0 is the command to stop kernel debugging, while fw ctl zdebug is used to clear the buffer while debugging remains active. Disabling the debug process is the most definitive way to avoid seeing its output.

3. Check Point Support Center, SK Article sk33208, "How to debug 'fw monitor'": This article provides a practical example of the debugging workflow. It instructs users to enable debugging with fw ctl debug -buf , perform actions, and then explicitly turn off debugging using fw ctl debug 0. This reinforces fw ctl debug 0 as the standard command to terminate the debugging process and its output.