Server Debugging

Server event messages can arise from different sources and be controlled by different configuration options. The following table summarizes sshd command-line options and server configuration keywords that affect logging; and describes where to find the output.

To	Use	Output Location	Notes
Debug a single client connection	-d debug_level	stderr	Use 1, 2, 3, or 99. (Values 4-98 are accepted, but are equivalent to 3.) With this option, sshd terminates after the first client connection closes. This option is independent of the setting for LogLevel.
Enable persistent debugging	-D debug_level	/etc/ssh2/logs	A debug file is created using the following file name format: debugYYMMDD_HHMMSS_uniqueID. This option is independent of the setting for LogLevel.
Suppress debug messages	-q QuietMode	N/A — affects syslog output only	This option overrides LogLevel.
View server startup messages	LogLevel	stderr	Output to stderr includes errors and warnings found while parsing sshd2_config.