Re: 127.0.0.1 isn't the same as localhost

[Werner Flamme]

Smith, Graham - Computing Technical Officer [05.01.2017 20:09]:
> Something simple that eluded me for a while today - I'll send this out just 
> in case it helps someone else.
> 
> In my control file I had:
> 
> allow 127.0.0.1
> 
> But I couldn't view monit status or monit summary on the command line. I kept 
> getting:

[...]
> That made me go back and look at the authentication, but all looked ok. I 
> swapped
> allow 127.0.0.1 for allow localhost and all was good again. I pinged localhost
> and it resolved to ::1   aha! so it's an ipv6 resolution not ipv4!
> I should have spotted this quicker. And of course ::1 works instead of 
> localhost in the control file.
> 
> This is 5.20.0 on Debian Jessie by the way. Probably the same happens in all 
> current distros.

This has nothing to do with Monit as a software. It is a problem with
any host that has entries in /etc/hosts that look like

127.0.0.1       localhost
::1             localhost ipv6-localhost ipv6-loopback

Here, you assign the same hostname (localhost) to two different IP
addresses. If you remove the single string "localhost" after "::1" and
leave the other entries on the line untouched, you have this problem
solved as well. That's how I handle it on my hosts for years now.

Werner

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