rpm: fix update error if working directory is missing

[Watson1978]

If /tmp/fluent/ was removed, it causes error when update to Fluent Package 6.0.x as following:

# dnf install ./fluent-package-5.0.9-1.el8.x86_64.rpm

# rm -rf /tmp/fluent/

# dnf install -y ./fluent-package-6.0.1-1.el8.x86_64.rpm
Last metadata expiration check: 0:55:01 ago on Tue Feb 10 05:05:41 2026.
Dependencies resolved.
====================================================================================================================================================================
 Package                                   Architecture                      Version                                  Repository                               Size
====================================================================================================================================================================
Upgrading:
 fluent-package                            x86_64                            6.0.1-1.el8                              @commandline                             23 M

Transaction Summary
====================================================================================================================================================================
Upgrade  1 Package

Total size: 23 M
Downloading Packages:
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                                            1/1
  Running scriptlet: fluent-package-6.0.1-1.el8.x86_64                                                                                                          1/1
  Running scriptlet: fluent-package-6.0.1-1.el8.x86_64                                                                                                          1/2
/var/tmp/rpm-tmp.Fp7H9o: line 39: /tmp/fluent/.local_base_plugins: No such file or directory
error: %prein(fluent-package-6.0.1-1.el8.x86_64) scriptlet failed, exit status 1

Error in PREIN scriptlet in rpm package fluent-package
  Verifying        : fluent-package-6.0.1-1.el8.x86_64                                                                                                          1/2
  Verifying        : fluent-package-5.0.9-1.el8.x86_64                                                                                                          2/2

Failed:
  fluent-package-5.0.9-1.el8.x86_64                                                fluent-package-6.0.1-1.el8.x86_64

Error: Transaction failed

[kenhys]

I come to think using /tmp/fluent is bad design failure.

So, it might be better to switch using /var/cache/fluent or something instead.
What do you think?
(If already /var/cache/fluent is used by user, need to care that too)

[Watson1978]

That makes sense.
it might be appropriate into /var/cache/fluent.

In additional, maybe we should replace /tmp/fluent/.main_pid into /var/run/fluent.main_pid or other.

[Watson1978]

In additional, maybe we should replace /tmp/fluent/.main_pid into /var/run/fluent.main_pid or other.

I did miss read.
main pid files already located in /var/run/fluent/fluentd.pid

# systemctl cat fluentd
# /usr/lib/systemd/system/fluentd.service
...

PIDFile=/var/run/fluent/fluentd.pid

...

[kenhys]

Could you add test case for downgrading to v6.0.0 or v6.0.1?
something like downgrade-to-v6-lts-tmpfiles.sh