This document will introduce you to the Message-ID and FQDN difficulties and help you out.
The unique fully-qualified domain name (or host name, FQDN or FQHN for short) is used by leafnode to generate the Message-ID.
What is the Message-ID?
Every message (mail or news) has a unique identifier in its header, the Message-ID. It may not be visible in your software unless you choose ``display all headers'' or ``display raw'' or ``display source''.
The Message-ID looks roughly like an E-Mail address, <12345.67890@host.example.com>: it has a local and a domain part, separated by an @ sign, only that the local part of the Message-ID is different for different pieces of mail or news, while the local part of the mail address is constant. The domain part is usually the name of the host that generated the Message-ID: your computer's name when you are sending mail or posting news.
Whenever a news server is offered a new news article for redistribution, it looks at the Message-ID to determine if it already has the article, to avoid double work, and to avoid that news articles run in circles.
Therefore, each message sent, mail or news, must have a unique Message-ID. If the Message-ID is not unique, because you use the same host name as somebody else, and you and the other person write an article at the same time, either article will be discarded by the server. Leafnode will tell you that the Message-ID of the article it is about to post is already in use upstream.
Please note that this problem is not leafnode-specific. Any software may suffer, but it's less prominent in mail, and it's difficult to see, because you're not getting a bounce back.
There are several ways to obtain one. When you got yours, see below on how to configure your domain name.
Again: This host name need not be entered into your DNS data base, just make sure only one computer uses this name at the same time.
news.cis.dfn.de:telnet news.cis.dfn.de 119
(wait until connected)
authinfo user sixpack authinfo pass joe quit
Replace ``sixpack'' and ``joe'' by your login and password. After the ``authinfo pass'' line, you should see a line that reads:
281 Authentication accepted. (UID=00000)
If you get a 481 line, please retry, you may have mistyped user name or password. Correcting these lines with Backspace or Delete may also lead to failed logins. Retry with careful typing so that you do not need to correct your input.
00000 shall be replaced by your actual user ID.
Your hostname then is ID-00000.news.dfncis.de. DO MAKE SURE TO REPLACE THE NUMBER IN ID-00000 by the number the server told you in the UID= LINE.
Your internet service provider may have reserved a special subdomain for the sole purpose of letting users create their own unique Message-IDs.
Well, it is probably the default name or domain that your OS vendor chose, like ``localhost.localdomain''. As such, it is not unique, but used on many computers, and therefore does not qualify as fully qualified domain name.
Many sites run resolvers that are based on ISC Bind code. And many sites configure their name servers so that they will resolve localhost.example.com. Therefore, localhost.example.com will not designate a single computer, but any computer that has ``localhost'' as a name. These resolvers are problematic because they will first see the domain as unqualified and append the domain or searchlist, so assuming that your domain is example.com, these resolvers will try localhost.example.com first, which will resolve to 127.0.0.1 at many sites.
(It is usually a mistake to add localhost to the name server for a
domain, the clients had better be fixed instead. As a workaround,
removing all domain and searchlist lines from /etc/resolv.conf will
usually work at the expense of not being able to use short names unless
they are listed in /etc/hosts.)
Preferably, the host name is entered into your system configuration so that it is available globally, to your mailers and news readers should they desire to create a FQDN.
How exactly the hostname is configured, depends on your system, it is usually a two-step approach, but your system installation/configuration software may simplify things for you.
1. Configure the bare hostname. Red Hat Linux and Mandrake Linux use
linuxconf. SuSE Linux 7.3 and older read it from FQHOSTNAME in
/etc/rc.config (but you can also use YaST or YaST2), FreeBSD 4.6 reads
it from hostname in /etc/rc.conf (but you can use
/stand/sysinstall).
2. On many systems, you will have to put the fully qualified host name
into /etc/hosts in addition to the place mentioned above. (On
networked systems, using NIS, DNS or LDAP is also feasible if the client
is configured to use the respective system to resolve host names.)
Usually, a computer that is to resolve a hostname will look at
/etc/hosts first and then at DNS.
An /etc/hosts line might look like this:
192.168.0.1 abacus.mid.example.com abacus oldname
Keep the original name of the computer as an alias in case you configured some other software to use the old name.
You can also write a line like
hostname = abacus.mid.example.com
into your /etc/leafnode/config. But I recommend against it, see the
next section:
You should configure the FQDN system-wide. Your news reader may generate a Message-ID itself, and it is not aware of leafnode's configuration and will generate an invalid Message-ID -- leafnode will then reject the posting because the Message-ID is invalid.