-Last modified: 25 July 2000 by Ian Maude, G0VGS
-
-
-This section describes the installation of DX Spider v1.35 on a
-I am assuming a general knowledge of Linux and its commands. You should know how to use tar and how to edit files using your favourite editor.
-
-
-The crucial ingredient for all of this is In addition to the standard Red Hat distribution you will require the following
-
-
-Do get the latest versions of these packages and install them but use the above list as the earliest versions usable.
-
-
-I will assume that you have already downloaded the latest tarball of the DXSpider software and are ready to install it. I am assuming version 1.35 for this section but of course you would use the latest version.
-
-
-Login as root and create a user to run the cluster under.
-
-Now set a password for the user ...
-
-
-Now to unpack the DX Spider distribution, set symbolic links and group permissions. Copy the tarball to /home/sysop and do the following.
-
-
-The next step is to set the permissions on the Spider directory tree and files ....
-
-
-This last step allows various users of the group spider to have write access to all the directories. This is not really needed just yet but will be useful when web interfaces start to appear.
-
-
-Finally, you need to fix the permissions on the ax25_call and netrom_call programs. Check where they are with the locate command and alter the permissions with the chmod command like this ..
-
-
-Now login to your machine as the user you created earlier. In my case that user is called sysop. Once logged in, issue the following commands ....
-
-
-Using the distributed DXVars.pm as a a template, set your cluster callsign, sysop callsign and other user info to suit your own environment. Note that this a perl file which will be parsed and executed as part of the cluster. If you get it wrong then perl will complain when you start the cluster process. It is important only to alter the text of any section. Some of the lines look a little odd. Take this line for example ....
-
-
-$myemail = "ianmaude\@btinternet.com";
-
-
-
-There appears to be an extra slash in there. However this has to be there for the file to work so leave it in.
-
-
-DON'T alter the DXVars.pm (or any other file) in /spider/perl, they are overwritten with every release. Any files or commands you place in /spider/local or /spider/local_cmd will automagically be used in preference to the ones in /spider/perl EVEN while the cluster is running!
-
-
-Save the new file and change directory to ../perl ....
-
-
-Now type the following command which creates the basic user file with you as the sysop.
-
-
-We can now bring spider up for the first time and see if all is well or not! It should look something like this ...
-
-
-If all is well then login on another term or console as sysop and cd to /spider/perl. Now issue the following command ...
-
-
-This should log you into the cluster as the sysop under the alias callsign we set earlier. In this case the callsign is G0VGS. The cluster callsign is set in the DXVars.pm file in /spider/local. In this case we will assume that this was set as GB7MBC. You should therefore see this when you login ....
-
-
-and both the cluster and the client should return to Linux prompts.
-
-
-In earlier versions of Spider, all the processes were Perl scripts. This was fine but with a lot of users your computer memory would soon be used up. To combat this a new client was written in "C". This client only works for incoming connects at the moment. Before you can use it though it has to be "made". CD to /spider/src and type make. You should see the output on your screen and hopefully now have a small C program called client. Leave it in this directory.
-
-
-As stated previously, the aim of this document is not to tell you how to configure Linux or the ax25 utilities. However, you do need to add a line in your ax25d.conf to allow connections to DXSpider for your users. For each interface that you wish to allow connections on, use the following format ...
-
-
-Allowing telnet connections is quite simple. Firstly you need to add a line in /etc/services to allow connections to a port number, like this ....
-
-
-This needs to be added above the standard services such as ftp, telnet etc. Once this is done, you need to restart inetd like this ....
-
- Now login as sysop and cd spider/perl. You can test that spider is accepting telnet logins by issuing the following command ....
-
-
-Assuming all is well, then try a telnet from your linux console ....
-
-
-You should now get the login prompt and be able to login as before.
-
-
-In order to allow cluster node connections, spider needs to know that the connecting callsign is a cluster node. This is the case whether the connect is incoming or outgoing.
-In spider this is a simple task and can be done in runtime.
-
-
-Start up the cluster as you did before and login as the sysop with client.pl.
-The cluster node I am wanting to make a connection to is GB7BAA but you would obviously use whatever callsign you required.
-At the prompt type ...
-
-
-The case does not matter as long as you have a version of DXSpider later than 1.33. Earlier versions required the callsign to be in upper case.
-
-
-That is now set, it is as simple as that. To prove it, login on yet another console as sysop and issue the command ...
-
-
-You should get an initialisation string from DXSpider like this ...
-
-
-Because DXSpider operates under Linux, connections can be made using just about any protocol; AX25, NETRom, tcp/ip, ROSE etc are all possible examples. Connect scripts live in the /spider/connect directory and are simple ascii files. Writing a script for connections is therefore relatively simple.
-
-
-The connect scripts consist of lines which start with the following keywords or symbols:-
-
-
-
-
-
-Both these examples assume that everything is set up properly at the other end. You will find other examples in the /spider/examples directory.
-
-
-You start the connection, from within a sysop enabled cluster login, by typing in the word connect followed by a script name like this ....
-
-
-With later versions of Spider there is a set/login command for users. This tells them when a user or node logs in or out. If you do not add a line to your scripts after the final line (or before the client line which should always be last if needed) then the login/logout information will be sent to users
-In a script, this might look like ...
-
-
-Ok, you should now have DXSpider running nicely and allowing connects by cluster nodes or users. However, it has to be shutdown and restarted manually and if connection scripts fail they have to be started again manually too, not much use if you are not at the console!
-So, in this section we will automate both. Firstly starting the cluster.
-
-
-This is not only a way to start the cluster automatically, it also works as a watchdog, checking the sanity of DXSpider and respawning it should it crash for any reason.
-Before doing the following, shutdown the cluster as you did earlier.
-
-
-Login as root and bring up the /etc/inittab file in your favourite editor. Add the following lines to the file near the end ...
-
-
-This will automatically start DXSpider on tty7 (ALT-F7) on bootup and restart it should it crash for any reason.
-
-
-As root type the command telinit q. DXSpider should start up immediately. You will see the output on tty7 and if you login as sysop you should find everything running nicely.
-
-
-So far so good, now to automate script connections...
-
-
-Login as sysop and create a file in /spider/local_cmd called crontab. Edit it with your favourite editor and add a line like this (I have included a comment)
-
-
-The callsign involved will be the callsign of the cluster node you are going to connect to. This will now check every 10 minutes to see if gb7xxx is connected, if it is then nothing will be done. If it is not, then a connect attempt will be started.
-
-
-There are probably lots of other things you could use this crontab file for. If you want to know more about it, look at the
-Starting with version 1.13 there is simple hop control available on a per
-node basis. Also it is possible to isolate a network completely so that you
-get all the benefits of being on that network, but can't pass on information
-from it to any other networks you may be connected to (or vice versa).
-
-
-In /spider/data you will find a file called hop_table.pl. This is the file that controls your hop count settings. It has a set of default hops on the various PC frames and also a set for each node you want to alter the hops for. You may be happy with the default settings of course, but this powerful tool can help to protect and improve the network. The file will look something like this ...
-
-
-Each set of hops is contained within a pair of curly braces and contains a series of PC frame types. PC11 for example is a DX spot. The figures here are not exhaustive but should give you a good idea of how the file works.
-
-
-You can alter this file at any time, including whilst the cluster is running. If you alter the file during runtime, the command load/hops will bring your changes into effect.
-
-
-It is possible to isolate networks from each other on a "gateway" node using the
- set/isolate <node_call> command.
-
-
-The effect of this is to partition an isolated network completely from another
-nodes connected to your node. Your node will appear on and otherwise behave
-normally on every network to which you are connected, but data from an isolated
-network will not cross onto any other network or vice versa. However all the
-spot, announce and WWV traffic and personal messages will still be handled
-locally (because you are a real node on all connected networks), that is locally
-connected users will appear on all networks and will be able to access and
-receive information from all networks transparently. All routed messages will
-be sent as normal, so if a user on one network knows that you are a gateway for
-another network, he can still still send a talk/announce etc message via your
-node and it will be routed across.
-
-
-The only limitation currently is that non-private messages cannot be passed down
-isolated links regardless of whether they are generated locally. This will change
-when the bulletin routing facility is added.
-
-
-If you use isolate on a node connection you will continue to receive all information from the isolated partner, however you will not pass any information back to the isolated node. There are times when you would like to forward only spots across a link (maybe during a contest for example). To do this, isolate the node in the normal way and put in a filter in the /spider/filter/spots directory to override the isolate. This filter can be very simple and consists of just one line ....
-
-
-There is a lot more on filtering in the next section.
-
-
-Filters can be set for spots, announcements and WWV. You will find the directories for these under /spider/filter. You will find some examples in the directories with the suffix .issue. There are two types of filter, one for incoming information and one for outgoing information. Outgoing filters are in the form CALLSIGN.pl and incoming filters are in the form in_CALLSIGN.pl. Filters can be set for both nodes and users.
-
-
-All filters work in basically the same way. There are several elements delimited by commas.
-There can be many lines in the filter and they are read from the top by the program.
-When writing a filter you need to think carefully about just what you want to achieve. You
-are either going to write a filter to accept or to reject.
-Think of a filter as having 2 main elements. For a reject filter, you would have a line
-or multiple lines rejecting the things you do not wish to receive and then a default
-line accepting everything else that is not included in the filter. Likewise, for an
-accept filter, you would have a line or multiple lines accepting the things you wish
-to receive and a default line rejecting everthing else.
-
-
-In the example below, a user requires a filter that would only return SSB spots
-posted in Europe on the HF bands. This is achieved by first rejecting the CW section
-of each HF band and rejecting all of VHF, UHF etc based on frequency.
-Secondly, a filter rule is set based on CQ zones to only accept spots posted in
-Europe. Lastly, a default filter rule is set to reject anything outside the filter.
-
-
-The actual elements of each filter are described more fully in the following sections.
-
-
-The elements of the Spot filter are ....
-
-
-There are 3 elements here to look at. Firstly, the action element. This is very simple and only 2 possible states exist, accept (1) or drop (0).
-
-
-The second element is the field_no. There are 13 possiblities to choose from here ....
-
-
-The third element tells us what to expect in the fourth element. There are 4 possibilities ....
-
-
-The fifth element is simply the hops to set in this filter. This would only be used if the filter was for a node of course and overrides the hop count in hop_table.pl.
-
-
-So, let's look at an example spot filter. It does not matter in the example who the filter is to be used for.
-So, what do we need in the filter? We need to filter the spots the user/node requires and also set a default rule for anything else outside the filter. Below is a simple filter that stops spots arriving from outside Europe.
-
-
-So the filter is wrapped in between a pair of square brackets. This tells Spider to look in between these limits. Then each line is contained within its own square brackets and ends with a comma.
-Lets look carefully at the first line. The first element is 0 (drop). Therefore anything we put on this line will not be accepted. The next element is 4. This means we are filtering by the spotter. The third element is the letter "a" which tells the program to expect an alphanumeric expression in the fourth element. The fourth element is a list of letters separated by the pipe symbol.
-
-
-What this line does is tell the program to drop any spots posted by anyone in the USA, Canada or Japan.
-
-
-The second line is the default rule for anything else. The "d" tells us this and the line simply reads... accept anything else.
-
-
-You can add as many lines as you need to complete the filter but if there are several lines of the same type it is neater to enclose them all as one line. An example of this is where specific bands are set. We could write this like this ....
-
-
-But the line below achieves the same thing and is more efficient ....
-
-
-
-
-It should be noted that the filter will start to be used only once a user/node has logged out and back in again.
-
-I am not going to spend any more time on these filters now as they will become more "comprehensive" in the near future.
-
-
-In the /spider/msg directory you will find a file called badmsg.pl.issue. Rename this to badmsg.pl and edit the file. The original looks something like this ....
-
-
-I think this is fairly self explanatory. It is simply a list of subject headers that we do not want to pass on to either the users of the cluster or the other cluster nodes that we are linked to. This is usually because of rules and regulations pertaining to items for sale etc in a particular country.
-
-
-In the same way as mail, there are some types of spot we do not wish to pass on to users or linked cluster nodes. In the /spider/data directory you will find a file called baddx.pl.issue. Rename this to baddx.pl and edit the file. The original looks like this ....
-
-
-Again, this is simply a list of names we do not want to see in the spotted field of a DX callout.
-
-
-
-One of the more important things a cluster sysop needs to do is to get information to his users. The simplest way to do this is to have a banner that is sent to the user on login. This is know as a "message of the day" or "motd". To set this up, simply create a file in /spider/data called motd and edit it to say whatever you want. It is purely a text file and will be sent automatically to anyone logging in to the cluster.
-
-
-If for any reason the cluster is down, maybe for upgrade or maintenance but the machine is still running, a message can be sent to the user advising them of the fact. This message lives in the /spider/data directory and is called "offline". Simply create the file and edit it to say whatever you wish. This file will be sent to a user attempting to log into the cluster when DXSpider is not actually running.
-
-
-You can set other text messages to be read by the user if they input the file name. This could be for news items or maybe information for new users. To set this up, make a directory under /spider called packclus. Under this directory you can create files called news or newuser for example. In fact you can create files with any names you like. These can be listed by the user with the command ....
-
-
-You can also store other information in this directory, either directly or nested under directories. One use for this would be to store DX bulletins such as the OPDX bulletins. These can be listed and read by the user. To keep things tidy, make a directory under /spider/packclus called bulletins. Now copy any OPDX or similar bulletins into it. These can be listed by the user in the same way as above using the show/files command with an extension for the bulletins directory you have just created, like this ....
-
-
-An example would look like this ....
-
-
-You will find a file in /spider/cmd/ called Aliases. First, copy this file to /spider/local_cmd/Aliases and edit this file. You will see something like this ...
-
-
-DXSpider receives all and any mail sent to it without any alterations needed
-in files. Because personal and bulletin mail are treated differently, there
-is no need for a list of accepted bulletin addresses. It is necessary, however,
-to tell the program which links accept which bulletins. For example, it is
-pointless sending bulletins addresses to "UK" to any links other than UK
-ones. The file that does this is called forward.pl and lives in /spider/msg.
-At default, like other spider files it is named forward.pl.issue. Rename it
-to forward.pl and edit the file to match your requirements.
-The format is below ...
-
-
-To force the cluster to reread the file use load/forward
-
-
-Distribution lists are simply a list of users to send certain types of
-mail to. An example of this is mail you only wish to send to other
-sysops. In /spider/msg there is a directory called distro. You
-put any distibution lists in here. For example, here is a file called
-SYSOP.pl that caters for the UK sysops.
-
-
-In later versions of Spider a simple console program is provided for the sysop. This has a type ahead buffer with line editing facilities and colour for spots, announces etc.
-To use this program, simply use console.pl instead of client.pl.
-
-
-To edit the colours, copy /spider/perl/Console.pl to /spider/local and edit the file with your favourite editor.
-
-
-Most maintenance tasks are automatic but there are some commands that are useful for a sysop. These are listed below in alphabetical order. The number in brackets following the command name is the permissions level needed to use the command.
-
-
-
-
-Send an announcement to Sysops only
-
-
-
-
-Start a connection process that will culminate in a new connection to the
-DX cluster <callsign>. This process creates a new 'client' process which will
-use the script in /spider/connect/<callsign> to effect the 'chat' exchange
-necessary to traverse the network(s) to logon to the cluster <callsign>.
-
-
-
-
-
-When you send messages the fact that you have forwarded it to another node
-is remembered so that it isn't sent again. When you have a new partner
-node and you add their callsign to your /spider/msg/forward.pl file, all
-outstanding non-private messages will be forwarded to them. This may well
-be ALL the non-private messages. You can prevent this by using these
-commmands:-
-
- catch GB7DJK all
- catch GB7DJK 300 301 302 303
-
-and to undo what you have just done:-
-
- uncatch GB7DJK all
- uncatch GB7DJK 300 301 302 303
-
-which will arrange for them to be forward candidates again.
-
-
-
-
-DBCREATE allows you to define a database in the system. It doesn't actually
-create anything, just defines it.
-
-The databases that are created are simple DB_File hash databases, they are
-therefore already 'indexed'.
-
-You can define a local database with the first form of the command eg:
-
- DBCREATE oblast
-
-You can also chain databases with the addition of the 'chain' keyword.
-This will search each database one after the other. A typical example
-is:
-
- DBCREATE sdx_qsl chain sql_ad
-
-No checking is done to see if the any of the chained databases exist, in
-fact it is usually better to do the above statement first then do each of
-the chained databases.
-
-Databases can exist offsite. To define a database that lives on another
-node do:
-
- DBCREATE buckmaster remote gb7dxc
-
-Remote databases cannot be chained; however, the last database in a
-a chain can be a remote database eg:
-
- DBCREATE qsl chain gb7dxc
-
-To see what databases have been defined do:
-
- DBAVAIL (or it will have been aliased to SHOW/COMMAND)
-
-It would be normal for you to add an entry into your local Aliases file
-to allow people to use the 'SHOW/<dbname>' style syntax. So you would
-need to add a line like:-
-
-
-
-
-If you want to import or update data in bulk to a database you can use
-this command. It will either create or update entries into an existing
-database. For example:-
-
- DBIMPORT oblast /tmp/OBLAST.FUL
-
-will import the standard OBLAST database that comes with AK1A into the
-oblast database held locally.
-
-
-
-
-DBREMOVE will completely remove a database entry and also delete any data
-file that is associated with it.
-
-There is no warning, no comeback, no safety net.
-
-For example:
-
- DBREMOVE oblast
-
-will remove the oblast database from the system and it will also remove
-the associated datafile.
-
-I repeat:
-
-There is no warning, no comeback, no safety net.
-
-You have been warned.
-
-
-
-
-Executing this command will only have an effect if you are running the cluster
-in debug mode i.e.
-
-
-Works just like the user command except that sysops can see ALL messages.
-
-
-
-
-Disconnect any <call> connected locally
-
-
-
-
-Export a message to a file. This command can only be executed on a local
-console with a fully privileged user. The file produced will be in a form
-ready to be imported back into the cluster by placing it in the import
-directory (/spider/msg/import).
-
-This command cannot overwrite an existing file. This is to provide some
-measure of security. Any files written will owned by the same user as the
-main cluster, otherwise you can put the new files anywhere the cluster can
-access. For example:-
-
- EXPORT 2345 /tmp/a
-
-
-
-
-This command sends out any information held in the user file which can
-be broadcast in PC41 protocol packets. This information is Name, QTH, Location
-and Homenode. PC41s are only sent for the information that is available.
-
-
-
-
-This command attempts to re-initialise a link to a (usually) AK1A node
-that has got confused, usually by a protocol loop of some kind. It may
-work - but you usually will be better off simply disconnecting it (or
-better, if it is a real AK1A node, doing an RCMD <node> DISC/F <your
-node>).
-
-Best of luck - you will need it.
-
-
-
-
-You can get rid of any message to or originating from your callsign using
-this command. You can remove more than one message at a time.
-
-As a sysop you can kill any message on the system.
-
-
-Delete a message (usually a 'bulletin') from the whole cluster system.
-
-This uses the subject field, so any messages that have exactly the same subject
-will be deleted. Beware!
-
-
-
-
-Reload the /spider/cmd/Aliases file after you have editted it. You will need to
-do this if you change this file whilst the cluster is running in order for the
-changes to take effect.
-
-
-
-
-Reload the /spider/data/bands.pl file if you have changed it manually whilst
-the cluster is running.
-
-
-
-
-Normally, if you change a command file in the cmd or local_cmd tree it will
-automatially be picked up by the cluster program. Sometimes it can get confused
-if you are doing a lot of moving commands about or delete a command in the
-local_cmd tree and want to use the normal one again. Execute this command to
-reset everything back to the state it was just after a cluster restart.
-
-
-
-
-If you change the /spider/perl/Messages file (usually whilst fiddling/writing ne
-commands) you can have them take effect during a cluster session by executing this
-command. You need to do this if get something like :-
-
-unknown message 'xxxx' in lang 'en'
-
-
-
-
-Reload the /spider/data/prefix_data.pl file if you have changed it manually whilst
-the cluster is running.
-
-
-
-
-MERGE allows you to bring your spot and wwv database up to date. By default
-it will request the last 10 spots and 5 WWVs from the node you select. The
-node must be connected locally.
-
-You can request any number of spots or wwv and although they will be appended
-to your databases they will not duplicate any that have recently been added
-(the last 2 days for spots and last month for WWV data).
-
-
-
-
-Alter message parameters like To, From, Subject, whether private or bulletin
-or return receipt (RR) is required or whether to keep this message from timing
-out.
-
-
-
-
-Send some arbitrary text to a locally connected callsign. No processing is done on
-the text. This command allows you to send PC Protocol to unstick things if problems
-arise (messages get stuck etc). eg:-
-
- pc gb7djk PC33^GB7TLH^GB7DJK^400^
-
-You can also use in the same way as a talk command to a connected user but
-without any processing, added of "from <blah> to <blah>" or whatever.
-
- pc G1TLH Try doing that properly!!!
-
-
-
-
-This command is used to estimate the quality of the link to another cluster.
-The time returned is the length of time taken for a PC51 to go to another
-cluster and be returned.
-
-Any visible cluster node can be PINGed.
-
-
-
-
-This command allows you to send nearly any command to another DX Cluster
-node that is connected to the system.
-
-Whether you get any output is dependant on a) whether the other system knows
-that the node callsign of this cluster is in fact a node b) whether the
-other system is allowing RCMDs from this node and c) whether you have
-permission to send this command at all.
-
-
-
-
-As a sysop you may read any message on the system
-
-
-
-
-You can remove this level with unset/debug <name>
-
-
-
-
-Connect a node to your system in such a way that you are a full protocol
-member of its network and can see all spots on it, but nothing either leaks
-out from it nor goes back into from the rest of the nodes connected to you.
-
-You can potentially connect several nodes in this way.
-
-You can see which nodes are isolated with the show/isolate (1) command.
-
-You can remove the isolation with the command unset/isolate.
-
-
-
-
-In order to get accurate headings and such like you must tell the system
-what your latitude and longitude is. If you have not yet done a SET/QRA
-then this command will set your QRA locator for you. For example:-
-
- SET/LOCATION 52 22 N 0 57 E
-
-
-
-
-You can show who is locked out with the show/lockout (9) command.
-
-To allow the user to connect again, use the command unset/lockout
-
-
-
-
-Tell the system that the call(s) are to be treated as AK1A cluster and
-fed PC Protocol rather normal user commands.
-
-From version 1.41 you can also set the following types of cluster
-
-
-
-
-From version 1.35 onwards neighbouring nodes are pinged at regular intervals (see
-SET/PINGINTERVAL), usually 300 seconds or 5 minutes. There is a 'pump-up'
-counter which is decremented on every outgoing ping and then reset to
-the 'obscount' value on every incoming ping. The default value of this
-parameter is 2.
-
-What this means is that a neighbouring node will be pinged twice at
-(default) 300 second intervals and if no reply has been heard just before
-what would be the third attempt, that node is disconnected.
-
-If a ping is heard then the obscount is reset to the full value. Using
-default values, if a node has not responded to a ping within 15 minutes,
-it is disconnected.
-
-
-
-
-As from version 1.35 all neighbouring nodes are pinged at regular intervals
-in order to determine the rolling quality of the link and, in future, to
-affect routing decisions. The default interval is 300 secs or 5 minutes.
-
-You can use this command to set a different interval. Please don't.
-
-But if you do the value you enter is treated as minutes up 60 and seconds
-for numbers greater than that.
-
-This is used also to help determine when a link is down at the far end
-(as certain cluster software doesn't always notice), see SET/OBSCOUNT
-for more information.
-
-
-
-
-Set the privilege level on a callsign. The privilege levels that pertain
-to commands are as default:-
-
-
-
-
-The password for a user can only be set by a full sysop. The string
-can contain any characters but any spaces are removed (you can type in
-spaces - but they won't appear in the password). You can see the
-result with STAT/USER. The password is the usual 30 character baycom
-type password.
-
-
-
-
-
-
-Show the name and location where every program module was load from. This
-is useful for checking where you think you have loaded a .pm file from.
-
-
-
-
-Shutdown the cluster and disconnect all the users. If you have Spider
-set to respawn in /etc/inittab it will of course restart.
-
-
-
-
-This is a very simple yet powerful command for the sysop. It allows you to
-issue commands as if you were a different user. This is very useful for the
-kind of things that users seem to always get wrong.. like home_node for
-example.
-
-
-
-
-Show the internal status of a database descriptor.
-
-Depending on your privilege level you will see more or less information.
-This command is unlikely to be of much use to anyone other than a sysop.
-
-
-
-
-Show the internal status of the channel object either for the channel that
-you are on or else for the callsign that you asked for.
-
-Only the fields that are defined (in perl term) will be displayed.
-
-
-
-
-This command shows the internal status of a message and includes information
-such as to whom it has been forwarded, its size, origin etc etc.
-
-
-
-
-Shows the full contents of a user record including all the secret flags
-and stuff.
-
-Only the fields that are defined (in perl term) will be displayed.
-
-
-
-