runcmd considers the exit code for the last command only

[bjornt]

Bug report

When using runmd, the last command in that list will determine the result of the runcmd
step. If the last command fails, cloud-init will report an error. If the last command
succeeds, all the previous command may fail, and cloud-init still reports success.

This is an inconsistency that I couldn't find in the documentation.

Steps to reproduce the problem

Use the following cloud-init config to see cloud-init report success:

#cloud-config
runcmd:
  - /bin/false
  - /bin/true

Use the following cloud-init config to see cloud-init report failure:

#cloud-config
runcmd:
  - /bin/true
  - /bin/false

Environment details

• Cloud-init version: 26.1-0ubuntu2
• Operating System Distribution: Ubuntu 26.04
• Cloud provider, platform or installer type: lxd

cloud-init logs

[nabil-rady]

The runcmd collects the commands and appends them line by line in a shell file. It's then executed in a later stage. It's mentioned in the docs here, although maybe not as obviously.

The expected behavior of running a POSIX compliant script is to return the status code of the last command.

[bjornt]

Right, it's not documented, so the question is whether it's supported. If this is the intended behavior, then it should be documented that all the commands will be appended to a script that's executed by bash (or whatever shell that's used).

For example, if I have the first command be "set -e", I can have cloud-init fail on the first failure. This works today, but will it work in the future?