Troubleshooting the Salt Minion¶

Running in the Foreground¶

A great deal of information is available via the debug logging system, if you are having issues with minions connecting or not starting run the minion in the foreground:

# salt-minion -l debug

Anyone wanting to run Salt daemons via a process supervisor such as monit, runit, or supervisord, should omit the -d argument to the daemons and run them in the foreground.

What Ports does the Minion Need Open?¶

No ports need to be opened on the minion, as it makes outbound connections to the master. If you've put both your Salt master and minion in debug mode and don't see an acknowledgment that your minion has connected, it could very well be a firewall interfering with the connection. See our firewall configuration page for help opening the firewall on various platforms.

If you have netcat installed, you can check port connectivity from the minion with the nc command:

$ nc -v -z salt.master.ip.addr 4505
Connection to salt.master.ip.addr 4505 port [tcp/unknown] succeeded!
$ nc -v -z salt.master.ip.addr 4506
Connection to salt.master.ip.addr 4506 port [tcp/unknown] succeeded!

The Nmap utility can also be used to check if these ports are open:

# nmap -sS -q -p 4505-4506 salt.master.ip.addr

Starting Nmap 6.40 ( http://nmap.org ) at 2013-12-29 19:44 CST
Nmap scan report for salt.master.ip.addr (10.0.0.10)
Host is up (0.0026s latency).
PORT     STATE  SERVICE
4505/tcp open   unknown
4506/tcp open   unknown
MAC Address: 00:11:22:AA:BB:CC (Intel)

Nmap done: 1 IP address (1 host up) scanned in 1.64 seconds

If you've opened the correct TCP ports and still aren't seeing connections, check that no additional access control system such as SELinux or AppArmor is blocking Salt. Tools like tcptraceroute can also be used to determine if an intermediate device or firewall is blocking the needed TCP ports.

Using salt-call¶

The salt-call command was originally developed for aiding in the development of new Salt modules. Since then, many applications have been developed for running any Salt module locally on a minion. These range from the original intent of salt-call (development assistance), to gathering more verbose output from calls like state.apply.

When initially creating your state tree, it is generally recommended to invoke highstates by running state.apply directly from the minion with salt-call, rather than remotely from the master. This displays far more information about the execution than calling it remotely. For even more verbosity, increase the loglevel using the -l argument:

# salt-call -l debug state.apply

The main difference between using salt and using salt-call is that salt-call is run from the minion, and it only runs the selected function on that minion. By contrast, salt is run from the master, and requires you to specify the minions on which to run the command using salt's targeting system.

Live Python Debug Output¶

If the minion seems to be unresponsive, a SIGUSR1 can be passed to the process to display what piece of code is executing. This debug information can be invaluable in tracking down bugs.

To pass a SIGUSR1 to the minion, first make sure the minion is running in the foreground. Stop the service if it is running as a daemon, and start it in the foreground like so:

# salt-minion -l debug

Then pass the signal to the minion when it seems to be unresponsive:

# killall -SIGUSR1 salt-minion

When filing an issue or sending questions to the mailing list for a problem with an unresponsive daemon, be sure to include this information if possible.

Multiprocessing in Execution Modules¶

As is outlined in github issue #6300, Salt cannot use python's multiprocessing pipes and queues from execution modules. Multiprocessing from the execution modules is perfectly viable, it is just necessary to use Salt's event system to communicate back with the process.

The reason for this difficulty is that python attempts to pickle all objects in memory when communicating, and it cannot pickle function objects. Since the Salt loader system creates and manages function objects this causes the pickle operation to fail.

Salt Minion Doesn't Return Anything While Running Jobs Locally¶

When a command being run via Salt takes a very long time to return (package installations, certain scripts, etc.) the minion may drop you back to the shell. In most situations the job is still running but Salt has exceeded the set timeout before returning. Querying the job queue will provide the data of the job but is inconvenient. This can be resolved by either manually using the -t option to set a longer timeout when running commands (by default it is 5 seconds) or by modifying the minion configuration file: /etc/salt/minion and setting the timeout value to change the default timeout for all commands, and then restarting the salt-minion service.

If a state.apply run takes too long, you can find a bottleneck by adding the --out=profile option.