Modules

Volant runs a module in one of three places: natively in the agent on the host, on the controller itself, or on the host through the warm Python path. A playbook that names a module this release does not support yet stops when it loads, before the first task, the way Ansible stops on a module it cannot resolve.

A module named in a file that only a dynamic include_tasks or include_role brings in is checked when a host reaches that statement. The statement then fails for that host and nothing in the file runs. See Includes and imports.

On the agent

The agent runs these on the host, without Python. The arguments column lists what each module reads.

Each argument is read as the playbook writes it. Ansible declares chdir, creates and removes as paths and expands ~ and $VAR in them before using the value. This release does not, so creates: ~/.provisioned looks for a directory literally named ~. No other argument is expanded either: Ansible runs command: /bin/echo $HOME with the variable already replaced, while Volant hands the program the five characters $HOME. A shell task prints the same thing under both engines, because there the shell does the expanding, not the module.

Module	Free-form	Arguments	What it does
command	yes	argv, chdir, cmd, creates, removes, stdin, stdin_add_newline, strip_empty_ends	Run a program directly, without a shell.
raw	yes	executable	Run a command line through the remote shell, with no module machinery around it.
shell	yes	argv, chdir, cmd, creates, executable, removes, stdin, stdin_add_newline, strip_empty_ends	Run a command line through a shell, sh unless executable names another.

These arguments exist in Ansible and are not supported yet: a playbook that uses them stops before the run reaches a host.

• command: expand_argument_vars: true
• shell: expand_argument_vars

On the controller

The controller runs these itself, so they need no connection to the host.

Module	Free-form	What it does
assert	no	Fail the task unless every condition in that holds.
debug	no	Print a message or the value of a variable.
fail	no	Fail the task with a message.
include_vars	yes	Read a file of variables and set them on the host, for the rest of the run.
pause	no	Wait for seconds or minutes. Volant cannot read keyboard input, so when standard input is a terminal, prompt and a pause with no duration are not supported yet. Without a terminal, a pause that asks for input prints a warning and continues at once, as Ansible does.
set_fact	no	Set facts for a host, for the rest of the run.
validate_argument_spec	no	Check a role’s arguments against the specification in meta/argument_specs.yml.

On the warm Python path

Every other module ansible-core ships is a Python module, and Volant runs it as one. The host needs a Python 3 interpreter, and the controller needs ansible-core to build the payload. The warm Python path explains how it works.

Modules from collections installed on the controller run the same way. The controller’s ansible-core resolves each name before the first connection, and Volant never installs a collection. If a play or one of its roles names a module from a collection that is not installed, the run stops before it reaches a host and prints the ansible-galaxy collection install command that fixes it. Volant refuses, by name, a module that its collection runs through an action plugin, because it does not run a collection’s action plugins. A module that only a dynamic include brings in is refused when a host reaches the include, which then fails for that host. Volant keeps a collection’s module under its full name, so that module never stands in for a builtin module or for another collection’s module with the same short name.

The exceptions are the modules ansible-core runs through an action plugin that Volant does not have yet. What the playbook asks for lives in the plugin, not in the module, so sending the module alone would do something else and call it a success. Those modules are not supported yet: Volant names them before the run reaches a host. Fact gathering still works: a play’s gather_facts runs the setup module directly.

Module	How it runs
add_host	not supported yet: needs the add_host action plugin
apt	Python module
apt_key	Python module
apt_repository	Python module
assemble	not supported yet: needs the assemble action plugin
async_status	not supported yet: needs the async_status action plugin
blockinfile	Python module
cron	Python module
deb822_repository	Python module
debconf	Python module
dnf5	Python module
dpkg_selections	Python module
expect	Python module
file	Python module
find	Python module
gather_facts	not supported yet: needs the gather_facts action plugin
get_url	Python module
getent	Python module
git	Python module
group	Python module
group_by	not supported yet: needs the group_by action plugin
hostname	Python module
iptables	Python module
known_hosts	Python module
lineinfile	Python module
mount_facts	Python module
package_facts	Python module
ping	Python module
pip	Python module
replace	Python module
rpm_key	Python module
script	not supported yet: needs the script action plugin
service_facts	Python module
set_stats	not supported yet: needs the set_stats action plugin
setup	Python module
slurp	Python module
stat	Python module
subversion	Python module
systemd	Python module
systemd_service	Python module
sysvinit	Python module
tempfile	Python module
uri	not supported yet: needs the uri action plugin
user	Python module
wait_for	Python module
wait_for_connection	not supported yet: needs the wait_for_connection action plugin
yum_repository	Python module

Through an action plugin

The controller runs these as the reference’s action plugins do: it picks or renders what reaches the host, then sends it as ordinary modules over the connection the task already has. reboot also waits for the host: it reconnects until the host answers with a new boot id. Action plugins describes each one.

Module	What it does
copy	Copy a file from the controller, or content:, to the host.
dnf	Install or remove packages with dnf or dnf5, whichever the host runs.
fetch	Copy a file from the host to the controller, under dest and nowhere else.
package	Install or remove packages with the host’s own package manager.
reboot	Reboot the host and wait until it has booted again.
service	Manage a service with the host’s own init system.
template	Render a template on the controller and copy the result to the host.
unarchive	Extract an archive read on the controller, or one already on the host.