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 |
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 |
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. |
 |