@@ -61,6 +61,24 @@ These options :

 The command line reference has the [complete list of daemon flags](../reference/commandline/daemon.md)

 with explanations.

+### Daemon debugging

+

+As noted above, setting the log level of the daemon to "debug" or enabling debug mode

+with `-D` allows the administrator or operator to gain much more knowledge about the

+runtime activity of the daemon. If faced with a non-responsive daemon, the administrator

+can force a full stack trace of all threads to be added to the daemon log by sending the

+`SIGUSR1` signal to the Docker daemon. A common way to send this signal is using the `kill`

+command on Linux systems. For example, `kill -USR1 <daemon-pid>` sends the `SIGUSR1`

+signal to the daemon process, causing the stack dump to be added to the daemon log.

+

+> **Note:** The log level setting of the daemon must be at least "info" level and above for

+> the stack trace to be saved to the logfile. By default the daemon's log level is set to

+> "info".

+

+The daemon will continue operating after handling the `SIGUSR1` signal and dumping the stack

+traces to the log. The stack traces can be used to determine the state of all goroutines and

+threads within the daemon.

+

 ## Ubuntu

 As of `14.04`, Ubuntu uses Upstart as a process manager. By default, Upstart jobs