When kernel debugging is initiated using fw ctl debug, the Check Point firewall kernel module does not write messages to a standard log file directly. Instead, it writes the debug information into a dedicated, circular buffer within the kernel's memory space. This method is highly efficient and minimizes performance impact on the system. To view and extract these messages from the buffer for analysis, the administrator must use the fw ctl kdebug command. This command reads the buffer's contents and prints them to the standard output, from where they can be redirected to a file.

A. Messages are written to /etc/dmesg file

/etc/dmesg is not a standard file for logging. The dmesg command reads the kernel ring buffer, which is separate from the dedicated Check Point firewall debug buffer.

C. Messages are written to SFWDIR

$FWDIR is the Check Point installation directory, which contains logs in $FWDIR/log. However, high-volume kernel debugs are not written here directly to avoid I/O overhead and performance degradation.

D. Messages are written to console and also /var/log/messages file

Writing verbose kernel debugs directly to the console would render it unusable. While some system messages go to /var/log/messages, Check Point uses a separate buffer to avoid flooding system logs.

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1. Check Point SecureKnowledge sk32558, "How to use 'fw ctl zdebug' and 'fw ctl kdebug' commands": This document explicitly states, "The debug messages are written into a buffer in kernel memory. The fw ctl kdebug command is used to read from this buffer and print the messages to the standard output." This directly supports the mechanism described in option B.

2. Check Point R81.20 CLI Reference Guide, Chapter "Firewall and Kernel Commands - fw", Page 212: The guide describes the function of fw ctl kdebug as "Prints the kernel debug buffer." This confirms that a specific buffer exists and fw ctl kdebug is the tool to access it, aligning perfectly with the correct answer.

3. Check Point SecureKnowledge sk86321, "Kernel Debugging on Gaia OS": This article details the kernel debugging procedure. In the "Procedure" section, Step 4 is "Run the fw ctl kdebug command to see the debug messages." This reinforces that the messages are held in a buffer pending collection by this specific command.