deb:rpm: stop editing settings for migration

[daipom]

This fix stops editing /etc/default/fluentd or /etc/sysconfig/fluentd for migration.
We shouldn't touch the settings for migration.

For migration of the config file, we make a symlink:

• /etc/fluent/fluent.conf => /etc/fluent/td-agent.conf

We stop migrating the log filename.
If need to output logs to the old filename td-agent.log, user needs to set the environmental variable.

[daipom]

This PR is originally motivated by the idea that the main migration target should be existing user service files and we should not do complicated migration processes for our own assumption.

In this case, users should migrate the user service file manually. Since we provide symlinks /etc/td-agent/ and /var/log/td-agent/, updating some paths should work:

* `LD_PRELOAD`

* `GEM_HOME`

* `GEM_PATH`

* `/opt/td-agent/bin/fluentd`

I assume the following script, for example.

sudo sed -i /etc/systemd/system/td-agent.service -e 's /opt/td-agent/lib/libjemalloc.so /opt/fluent/lib/libjemalloc.so g'
sudo sed -i /etc/systemd/system/td-agent.service -e 's /opt/td-agent/lib/ruby/gems/2.7.0/ /opt/fluent/lib/ruby/gems/3.2.0/ g'
sudo sed -i /etc/systemd/system/td-agent.service -e 's /opt/td-agent/lib/ruby/gems/2.7.0/ /opt/fluent/lib/ruby/gems/3.2.0/ g'
sudo sed -i /etc/systemd/system/td-agent.service -e 's /opt/td-agent/bin/fluentd /opt/fluent/bin/fluentd g'
echo "Alias=fluentd.service" | sudo tee -a /etc/systemd/system/td-agent.service

This should be done by users manually, I think.

[daipom]

Recently, ServerSpec test for RockyLinux8 often fails and we can't confirm the results of systemd tests.
To check the results, I ran the tests without ServerSpec test on my fork.
The tests for yum are stable.

• https://github.com/daipom/fluent-package-builder/actions/runs/5664397584

[kenhys]

By the way, how about testing with /etc/systemd/system/td-agent.d/override.conf?

[daipom]

By the way, how about testing with /etc/systemd/system/td-agent.d/override.conf?

Thanks. I will separate the fixes about user service file tests from this PR.
I will consider it later!

[daipom]

yum tests are all green in my fork(without serverspec test): https://github.com/daipom/fluent-package-builder/actions/runs/5666906256

The Jammy test fails because some gem paths of v450 are different from other platform.
It is just a problem of tests.
I will separate these new tests from this PR since it is not directly related to this PR.

[daipom]

I will separate the fixes about user service file tests from this PR.

Done.

[kenhys]

LGTM.

[daipom]

Thanks for your review!