Add CACHE_SIZE to setupVars

[DirkJanIT]

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---

What does this PR aim to accomplish?:
https://discourse.pi-hole.net/t/add-cache-size-to-setupvars-conf/28667

How does this PR accomplish the above?:
Adds the necessary variable to setupVars.conf.

What documentation changes (if any) are needed to support this PR?:
Document the addition of CACHE_SIZE in setupVars.conf.

[dschaper]

https://docs.pi-hole.net/ftldns/dns-cache/ will need to be aligned with this PR.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/add-cache-size-to-setupvars-conf/28667/56

[DL6ER]

@dschaper Are you okay with overwriting Travis here? It seems to be dead.

[dschaper]

No, travis is failed for a reason. Note the branches.

The base branch was changed.

[DL6ER]

@dschaper Are you still okay with this being merged? If so, please go ahead.

[dschaper]

Need the .travis.yml file from master (or development) to be merged in to the PR so travis will check it.

[DL6ER]

The source repository doesn't exist any more

[dschaper]

If you think it's a good PR then we can override it.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-core-web-v5-2-and-ftl-v5-3-released/40909/1

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/correct-way-to-change-cache-setting/42699/2

[o5ky]

FYI this breaks when you upgrade from a previous older version using the command below. It inserts the variable instead of the variable value.
/etc/.pihole/automated\ install/basic-install.sh --repair --unattended

cache-size=@CACHE_SIZE@

FTL failed to start due to error at line 32 of /etc/dnsmasq.d/01-pihole.conf

[dschaper]

Is there a reason you didn't want to use the built in upgrade process of pihole -up instead of an undocumented and unsupported command line?

[o5ky]

I mean that is how to repair and it's a supplied script, it's sometimes required when the system has failed and requires the repair switch.