SSH Wrapper

Salt-SSH Background

Salt-SSH works by creating a tar ball of salt, a bunch of python modules, and a generated short minion config. It then copies this onto the destination host over ssh, then uses that host's local python install to run salt-client --local with any requested modules. It does not automatically copy over states or cache files and since it is uses a local file_client, modules that rely on cp.cache* functionality do not work.

SSH Wrapper modules

To support cp modules or other functionality which might not otherwise work in the remote environment, a wrapper module can be created. These modules are run from the salt-master initiating the salt-ssh command and can include logic to support the needed functionality. SSH Wrapper modules are located in /salt/client/ssh/wrapper/ and are named the same as the execution module being extended. Any functions defined inside of the wrapper module are called from the salt-ssh module.function argument command rather than executing on the minion.

State Module example

Running salt states on an salt-ssh minion, obviously requires the state files themselves. To support this, a state module wrapper script exists at salt/client/ssh/wrapper/, and includes standard state functions like apply, sls, and highstate. When executing salt-ssh minion state.highstate, these wrapper functions are used and include the logic to walk the low_state output for that minion to determine files used, gather needed files, tar them together, transfer the tar file to the minion over ssh, and run a state on the ssh minion. This state then extracts the tar file, applies the needed states and data, and cleans up the transferred files.

Wrapper Handling

From the wrapper script any invocations of __salt__['some.module']() do not run on the master which is running the wrapper, but instead magically are invoked on the minion over ssh. Should the function being called exist in the wrapper, the wrapper function will be used instead.

One way of supporting this workflow may be to create a wrapper function which performs the needed file copy operations. Now that files are resident on the ssh minion, the next step is to run the original execution module function. But since that function name was already overridden by the wrapper, a function alias can be created in the original execution module, which can then be called from the wrapper.


The saltcheck module needs sls and tst files on the minion to function. The invocation of saltcheck.run_state_tests is run from the wrapper module, and is responsible for performing the needed file copy. The saltcheck execution module includes an alias line of run_state_tests_ssh = salt.utils.functools.alias_function(run_state_tests, 'run_state_tests_ssh') which creates an alias of run_state_tests with the name run_state_tests_ssh. At the end of the run_state_tests function in the wrapper module, it then calls __salt__['saltcheck.run_state_tests_ssh'](). Since this function does not exist in the wrapper script, the call is made on the remote minion, which then having the needed files, runs as expected.