cloud-init - the first-boot initialisation of cloud instances (user data, SSH keys, hostname, packages)

Options you will use

status

did the boot stages finish? done, running, error, degraded (done with warnings)

--long

with the details: extended status, last update, the errors

--wait

block until cloud-init has finished

query KEY

read instance data (v1.instance_id, v1.region, v1.availability_zone ...)

Examples

$ cloud-init status --long

did the user data succeed, and if not, which module failed

$ sudo tail -50 /var/log/cloud-init-output.log

what the script printed

Gotchas

• Exit status of status: 0 done, 1 error, 2 degraded (recoverable errors).
• What the user data printed is in /var/log/cloud-init-output.log; cloud-init's own log is /var/log/cloud-init.log. The same output is in aws ec2 get-console-output from outside.
• User data runs ONCE, at the first boot, as root. Changing it on a stopped instance does nothing unless you make it run again (a launch template version + instance refresh is the usual way).