.. _cce-boot-cmds:

Run commands during boot
************************

Both ``runcmd`` and ``bootcmd`` can be used to run commands during the boot
process. They contain either a list of lists or a list of strings. Each item is
run in order, with output printed to the console.

The list must be written in proper YAML -- be sure to quote any characters
such as colons (``:``) that would otherwise be "eaten".

- ``runcmd`` only runs on first boot, **after** the instance has been started
  and all other configuration has been applied. In general, you should use
  ``runcmd`` unless you need to run something earlier in boot.
- ``bootcmd`` runs on every boot, and is typically used to run commands very
  early in the boot process (just after a boothook, and often before other
  cloud-init modules have run).

For a full list of keys for these two modules, refer to the
:ref:`runcmd module <mod_cc_runcmd>` and :ref:`bootcmd module <mod_cc_bootcmd>`
schema.

Run commands on instance initialization
=======================================

.. literalinclude:: ../../../module-docs/cc_runcmd/example1.yaml
   :language: yaml
   :linenos:

.. note::
   Don't write files to ``/tmp`` from cloud-init -- use ``/run/somedir``
   instead. Early boot environments can race ``systemd-tmpfiles-clean`` (LP:
   #1707222).

Run commands in early boot
==========================

The ``cloud-init-per`` command can be used to make ``bootcmd`` run exactly
once.

.. literalinclude:: ../../../module-docs/cc_bootcmd/example1.yaml
   :language: yaml
   :linenos: