Merge pull request #21316 from estesp/daemon-dump-stack-note

Add documentation on the stack trace dump capability of the daemon
This commit is contained in:
Sebastiaan van Stijn 2016-03-18 14:29:55 +01:00
commit d2a8621b20

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@ -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