Re: why do the comments in bacula-dir.conf say not to use "localhost" here?

Avahi is a decentralized local hostname resolution protocol.

Here is the text of my avahi configuration notes. These are red hat /
centos / rocky linux / alma linux centric. I specifically used them on
Rocky Linux 9.x. I hope you can get the general idea. The most important
things I think you need to know is that you will need to set up the avahi
daemon on your server, and that there are avahi-specific ping and resolver
tools to verify that avahi is working correctly.

Additionally, the following text is formatted like a bash script, with #
signs used to add comments. It is NOT a script, and shouldn't be dropped
into place as such.

notes begin:
# avahi mdns setup, for resolving names using multicast DNS, when local DNS
isn't awesome.

sudo dnf install avahi avahi-tools nss-mdns

sudo systemctl enable --now avahi-daemon

nano /etc/nsswitch.conf
OR
nano /etc/authselect/user-nsswitch.conf # preferred, nsswitch will get
overwritten by user-nsswitch

# find the line like:
hosts: files dns

# It should look like: # in my case, it was already correct, no need to
change)
hosts: files mdns4_minimal [NOTFOUND=return] dns


Test:
ping hostname.localtld
OR
avahi-resolve-host-name hostname.localtld

# If that doesn't work out of the box, maybe try dropping the firewall.

# I had to let mdns through the firewall.
# sudo firewall-cmd --get-active-zones
# should see output like
public
  interfaces: eth0
# probably only relevant to verify what zones you have configured.

# list services to see if mdns is allowed.
sudo firewall-cmd --zone=public --list-services

# if mdns isn't listed, add its service to the list:
sudo firewall-cmd --zone=public --add-service=mdns --permanent
sudo firewall-cmd --reload

# list services to see if mdns is allowed.
sudo firewall-cmd --zone=public --list-services

Test:
ping hostname.localtld
OR
avahi-resolve-host-name hostname.localtld


Regards,
Robert Gerber
402-237-8692
[email protected]


On Mon, Sep 1, 2025 at 3:51 PM Rob Gerber <[email protected]> wrote:

> To my understanding, we are advised not to use "localhost" because those
> address fields may be used to communicate "this is the director / SD
> address" to an external client. This is my guess. Someone else would need
> to confirm, or you can check the (very verbose) documentation.
>
> FYI, the best way to search the documentation is to download the pdf and
> search it. HTML manual search across multiple pages isn't possible for some
> bizarre reason. All of this is in my experience, anyhow.
>
> In an environment where local hostname resolution isn't handled by the
> router or some other central authority, I have used avahi on my bacula
> server. Avahi is a peer to peer name resolution system. I believe avahi is
> what windows machines are using to resolve LAN hostnames in environments
> where the router or DNS server isn't handling that for them. In any case,
> it got me out of a similar jam once.
>
> I believe that it would be suitable to use either a hostname or LAN IP
> address, as long as the relevant clients can resolve / reach either of
> those. You will need suitable firewall rules on the server and possibly the
> client, of course. If you previously tried the server's LAN IP address, and
> that didn't work (and you also restarted the bacula dir/sd after making the
> configuration changes), I'd try temporarily disabling the firewall on the
> server / client to see I'd that resolves the issue.
>
> Please remember to restart the bacula-dir and bacula-sd after changing
> their configuration files.
>
> Here is some information on firewalls and bacula. Please note that the
> author of this documentation mentions server config files 'server-dir.conf'
> and 'server-sd.conf'. These are simply what he has chosen to name his
> config files, and he has referenced them from within the bacula-dir.conf /
> bacula-sd.conf files. For your purposes, just pretend he wrote
> 'bacula-dir.conf' and 'bacula-sd.conf'.
>
>
> https://www.bacula.org/15.0.x-manuals/en/problems/Dealing_with_Firewalls.html
>
> And of course, here is the bacula manual, in PDF form:
> https://www.bacula.org/15.0.x-manuals/en/main/main.pdf
>
> And the documentation in general:
> https://www.bacula.org/documentation/documentation/
>
> I am *NOT* saying 'RTFM'. It is a *very* large manual (700+ pages
> currently). I want you to have the same resources I used to reach a greater
> understanding of bacula. Asking this mailing list was one of the resources
> I used. Feel free to continue asking questions here. :)
>
> I will send some of my avahi configuration notes in a follow-on email.
>
> Robert Gerber
> 402-237-8692
> [email protected]
>
> On Mon, Sep 1, 2025, 3:08 PM Gary Dale <[email protected]> wrote:
>
>> I'm running Debian 13 (Trixie) on an AMD64 system.
>>
>> I've been struggling to get bconsole to connect to the storage-director.
>> After initially trying to set up a reverse lookup for the server name, I
>> took the easy way out and replaced the name with the IP address in the
>> autochanger section of bacular-dir.conf. That didn't help.
>>
>> The reason I was doing all this is immediately above the Address - line
>> in that section, it specifically says "Do not use "localhost" here".
>> Furthermore, the line itself says "N.B. Use a fully qualified name here".
>>
>> However, it appears that localhost, or more specifically 127.0,0.1, is
>> the only address that works.
>>
>>  From what I've been reading, if you do follow the "N.B.", you need to
>> ensure that there is a working reverse DNS lookup for it in order to
>> work. However that need should be removed by using an IP address
>> instead.  But if you are running the bacula director on the same device
>> as the storage director, it appears that you must use the Localhost IP
>> (127.0.0.1).
>>
>> Can someone please revise the comments to be more reflective of a
>> typical situation?
>>
>>
>>
>> _______________________________________________
>> Bacula-users mailing list
>> [email protected]
>> https://lists.sourceforge.net/lists/listinfo/bacula-users
>>
>

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