How to re-run cloud-init

How to fully re-run cloud-init

Most cloud-init configuration is only applied to the system once. This means that simply rebooting the system will only re-run a subset of cloud-init. Cloud-init provides two different options for re-running cloud-init for debugging purposes.

Warning

Making cloud-init run again may be destructive and must never be done on a production system. Artefacts such as ssh keys or passwords may be overwritten.

Remove the logs and cache, then reboot

This method will reboot the system as if cloud-init never ran. This command does not remove all cloud-init artefacts from previous runs of cloud-init, but it will clean enough artefacts to allow cloud-init to think that it hasn’t run yet. It will then re-run after a reboot.

cloud-init clean --logs --reboot

Run a single cloud-init module

If you are using user data cloud-config format, you might wish to re-run just a single configuration module. Cloud-init provides the ability to run a single module in isolation and separately from boot. This command is:

$ sudo cloud-init single --name cc_ssh --frequency always

Example output:

...
Generating public/private ed25519 key pair
...

This subcommand is not called by the init system. It can be called manually to load the configured datasource and run a single cloud-config module once, using the cached user data and metadata after the instance has booted.

Note

Each cloud-config module has a module FREQUENCY configured: PER_INSTANCE, PER_BOOT, PER_ONCE or PER_ALWAYS. When a module is run by cloud-init, it stores a semaphore file in /var/lib/cloud/instance/sem/config_<module_name>.<frequency> which marks when the module last successfully ran. Presence of this semaphore file prevents a module from running again if it has already been run.

Inspect cloud-init.log for output of what operations were performed as a result.

How to partially re-run cloud-init

If the behavior you are testing runs on every boot, there are a couple of ways to test this behavior.

Manually run cloud-init stages

Note that during normal boot of cloud-init, the init system runs these stages at specific points during boot. This means that running the code manually after booting the system may cause the code to interact with the system in a different way than it does while it boots.

cloud-init init --local
cloud-init init
cloud-init modules --mode=config
cloud-init modules --mode=final

Reboot the instance

Rebooting the instance will take a little bit longer, however it will make cloud-init stages run at the correct times during boot, so it will behave more correctly.

reboot -h now