cloud-init strips ending newline from "/var/lib/cloud/data/previous-hostname"

[Anirban Sinha]

Steps to Reproduce:
1. enable cloud-init for rhel8

Actual results:
[root@mj-rhel87 ~]# cat /etc/hostname
mj-rhel87
[root@mj-rhel87 ~]# cat /var/lib/cloud/data/previous-hostname
mj-rhel87[root@mj-rhel87 ~]#

2023-03-28 14:47:45,733 - util.py[DEBUG]: Reading from /var/lib/cloud/data/previous-hostname (quiet=False)
2023-03-28 14:47:45,734 - util.py[DEBUG]: Read 9 bytes from /var/lib/cloud/data/previous-hostname
2023-03-28 14:47:45,734 - subp.py[DEBUG]: Running command ['hostname'] with allowed return codes [0] (shell=False, capture=True)
2023-03-28 14:47:45,738 - __init__.py[INFO]: /var/lib/cloud/data/previous-hostname differs from /etc/hostname, assuming user maintained hostname.

Expected results:
file /var/lib/cloud/data/previous-hostname will be terminated with new line as well

The issue is seen on RHEl 7, RHEL 8 and RHEL 9.

Ubuntu doesn't have this problem.
-------------
ubuntu@xiachen-test-ubuntu:~$ cat /etc/hostname
xiachen-test-ubuntu
ubuntu@xiachen-test-ubuntu:~$ cat /var/lib/cloud/data/previous-hostname
xiachen-test-ubuntu
ubuntu@xiachen-test-ubuntu:~$

[Anirban Sinha (anisinha)]

Posted a PR: https://github.com/canonical/cloud-init/pull/2108

[Chad Smith (chad.smith)]

Thanks Anirban for submitting the PR and Aciba for review/landing here. Marking Fix committed.

[Chad Smith (chad.smith)]

Expect this fix released in cloud-init version 23.2

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/4096