diff --git a/docs/admin/configuring.md b/docs/admin/configuring.md index b50d0d755e..09ed39dd3b 100644 --- a/docs/admin/configuring.md +++ b/docs/admin/configuring.md @@ -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 ` 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