Just a big fat No on trying just any command with sudo!
It is running. 
that is because you did sudo service pihole-FTL start why did you want to start it afterwards another time by calling it directly?
I just wanted to list the output of all possible combinations, for you to evaluate.
By default, I don't do anything with pihole-FTL, the settings page indicated FTL was running,
I just tried pihole-FTL to see if there was any help available. (config-file, settings, ...) but apparently, there isn't.
Still wondering why the error message appears when simply running pihole-FTL...
In the process of setting up the system from scratch (again) to see if I find something new...
Which error do you refer to?
pihole-FTL
FATAL: Opening of FTL log (/var/log/pihole-FTL.log) failed!
Make sure it exists
That is exactly what happens, you are trying to start pihole-FTL as your own process (whatever user you might be). However, I'm pretty sure you are not the user pihole. However, the log file /var/log/pihole-FTL.log can only be opened with write-access from the user pihole (because it owns it and all other users are only allowed to read, but not to write to this file).
As always: I'm not a native speaker and happily accept and discuss suggestions of improvements of any messages.
User = pi.
It just seems to me pihole-FTL should produce a more useful message when already running e.g. some help or user and PID or ...
As I said before, everything seems to be functioning, I just started looking for what's new.
Yeah, the first check is if it can open the log file and it will fail miserably if this is not the case (because it will not even be able to log anything when started in the background). It won't even check for other running instances of FTL at this point.
I am testing the FTL as well, on a Debian 9 VM. Let us know if anything in particular is to be tested.
FTL version: v1.5.1
Process identifier (PID): 596
Time FTL started: 10:12:38
User / Group: pihole / pihole
Total CPU utilization: 0.1%
Memory utilization: 1.7%
Used memory: 4.02 MB
Just do whatever you can think of to it. Use it otherwise as you would normally.
I did several tests on low power VMs and that works absolutely flawlessly and fast.
How can you get so much DNS Requests???!!!
Pi-hole can very well be used in business environments with more than fifty concurrently active clients without any issues. But for getting up to this humongous number of queries, I used a small script that queries for random domains (obviously most of them didn't even exist) for several hours.
ah okay good to know well i'm trying it in out at my working place and getting bigger and bigger at the moment i'm trying with 10 clients working quiet fine
FTL stopped working after updating. Here's a debug token FYI - vuvngfx5w5
Shows lost connection to API on the front page.
::: Pi-hole version is v2.13.1-168-gd38e034 (Latest version is v2.13.2) ::: Web-Admin version is v2.5.2-124-g5092133 (Latest version is v2.5.2) Pi-hole FTL (Running) FTL version: v1.9 Process identifier (PID): Time FTL started: User / Group: / Total CPU utilization: % Memory utilization: % Used memory: 0 bytes
Please upload also the FTL log:
tail -n100 /var/log/pihole-FTL.log | nc tricorder.pi-hole.net 9999
and provide the token
Ok, done - f2odxc1w69
It looks like there are multiple pihole-FTL running. Have you tried to run it as root recently (please don't do that)?
Please try
sudo service pihole-FTL restart
FTL restart didn't change anything. I did a system restart too. Tried a repair and also reconfigure. I had been on this root account since the system was installed. Nothing has changed recently.
We just released a new version of FTL with increased logging verbosity.
EDIT: If the problem persists, please upload the pihole-FTL.log, again
It's working nowFTL is down again - I reverted to an earlier snapshot, uninstalled pihole, and installed it again, and checked out dev. Here's the tokens FYI - hkb1p83nhx & 49rh62osnn (via the tail command above)
Can you confirm that the pihole-FTL.log file is truncated like this?
[2017-04-03 13:01:27.461] Finished initial log file parsing
[2017-04-03 13:01:27.461] -> Total DNS queries: 0
[2017-
EDIT
There are detailed debug instructions for FTL: Restart FTL · Issue #12 · pi-hole/FTL · GitHub
I'd be very glad if you find the time to help us getting to know what is going on with your FTL engine