Salt local testing

For testing locally, use salt-call --local instead of salt '*'. This needs privileged access, so it should probably be done in a VM or a container.

The following command sends a ping command to all the machines on the roster (or, later, all connected minions).

$ salt '*' test.ping

They are all supposed to return True. This command fails if machines are unreachable, SSH credentials are wrong, or other common configuration problems.

Because this command does not affect the remote machines, it is a good idea to run it first before starting to perform any changes. This ensures that the system is correctly configured.

Several other test functions are used for more sophisticated checks of the system.

The test.false command intentionally fails, which is useful to see what failures look like. For example, when running Salt via a higher-level abstraction, such as a continuous deployment system, this can be useful to see visible failures (for example, send appropriate notifications).

The test.collatz and test.fib functions perform heavy computations and return the time it took and a result. It is used to test performance; for example, this might be useful if machines dynamically tune CPU speed according to available power or external temperature. You want to test whether this is the cause of performance problems.

On the salt command line, many things are parsed into Python objects. The interaction of the shell parsing rules and the Salt parsing rules can sometimes be hard to predict. The test.kwarg command can be useful when checking how things are parsed. It returns the value the dictionary passed in as keyword arguments; for example, the following returns the dictionary of the keywords.

Since the combination of the shell parsing rules and the Salt parsing rules can be, at times, hard to predict, this is a useful command to be able to debug those combinations and figure out what things are over- or underquoted.

Instead of '*' you can target a specific machine by logical name. This is often useful when seeing a problem with a specific machine. It allows a quick feedback mechanism when trying various fixes (for example, changing firewall settings or SSH private keys).

While testing that the connection works well is important, the reason to use Salt is to control machines remotely. While the main usage of Salt is to synchronize to a known state, Salt can also be used to run ad hoc commands.

$ salt '*' cmd.run 'mkdir /src'

This causes all connected machines to create a /src directory. More sophisticated commands are possible, and it is possible to only target specific machines.