~sbeattie/ubuntu/natty/logwatch/logwatch-fixups

First of all, each filter must process data from one or more "Logfile

Group".

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* Logfile Groups

***********************************************

Logfile groups are defined by a configuration file in

/etc/log.d/conf/logfiles named <logfile_group_name>.conf.  It is usually

easier to copy an existing logfile group configuration than it is to create

a brand new one.

There is only one required line in the logfile group config file.  This

command is called 'LogFile'.

# This will be the logfile named 'messages' in the default logfile

# directory (probably /var/log).

LogFile = messages

# You can also give this command with an absolute path, like this:

LogFile = /var/log/messages

You can have as many LogFile entries as you wish.  All the files specified

will be merged into one input stream for any filters that use this logfile

group.  You can also use standard wildcards when you specify the filename.

Another command that is optional is called 'Archive'.  You can specify a

file to also include in the data stream if the '--archives' option is used.

If these files do not exist it is okay.  For example:

# These 2 'Archive' entries will allow users of most Red Hat Linux

# systems to access their archives of the 'messages' logfile:

Archive = messages.?

# If they configure Compression to be on in /etc/logrotate.conf:

Archive = messages.?.gz

# It is best just to include both of these so that the logfile group

# will work for most systems.

Now, the general theory is that the LogFile Group should apply the date

range requested.  If the logfile is in the standard syslog format, you can

use the shared script 'ApplyStdDate' to filter out only the appropriate log

entries.  The way to call shared scripts (located in

/etc/log.d/scripts/shared) is:

*ApplyStdDate = 

Anything following the equal sign will be passed to the program as arguments

(the equal sign can be eliminated if no arguments are needed).  You should

look at the current logfile group config files for examples.

Finally, if the directory /etc/log.d/scripts/logfiles/<logfile_group_name>/

exists, any scripts in that directory will be executed.  All of these

scripts take the contents of all the specified logfiles in through STDIN and

output the modified logfile trought STDOUT.  These scripts can be written in

any language that can be executed on your system.

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* Service Filter Configuration File

***********************************************

Okay, once you have defined one or more logfile groups (or decided on one or

more existing logfile groups), you need to define your service filter.

This file needs to be in /etc/log.d/conf/services/ and it needs to be named

service.conf.  You should probably copy an existing config for another

service to create a new one.  

There is only one required line.  This is the command 'LogFile'.  The

LogFile command allows you to specify one or more *LogFile Groups* (as

described above) that this filter will process.  Remember, any filter can

process any number of LogFile Groups, and any LogFile Group may contain the

data from any number of logfiles (and archives). 

For a service filter that needs messages from /var/log/messages you would

add this line:

LogFile = messages

NOTE:  This is *not* because the name of the logfile is 'messages', but it

is because the name of the LogFile Group that has been defined is

'messages'.

You can have commands in the form of:

*SharedScriptName = Arguments

that will execute a script found in the /etc/log.d/scripts/shared/

directory named 'SharedScriptName' with arguments 'Arguments'.

This filter will modify the input to the service's filter.

You can also have commands in the form:

$EnvironmentVariable = Value

This command will set the 'EnvironmentVariable' environment variable to the

value 'Value'.  This environment variable will be accessable by your filter

program.

You will also usually want to specify a title for your script (new in

Logwatch 4.0).  If specified, then a start and stop delimiter will be added

by Logwatch for your specific service (with your script's output between

those delimiters).  This will *only* happen if you produce output.  If you

produce no output, the headers will not be created.  Here is how you define

your title:

Title = "My Service Title"

***********************************************

* Service Filter Executable

***********************************************

Once everything above has been done, you are ready to actually write

your filter.  This can be done in any language as all it does is:

1) Read logfile entries from STDIN

2) Access some environment variables

3) Generate a report on STDOUT

Before you try to write a filter, you should create the filter and make its

contents the test script given below.  The filter needs to be located in

/etc/log.d/scripts/services/ and named service (because you named the

config file service.conf).

###################### Cut Here #########################

#!/bin/bash

# This is as nice script that will show you the lines you will

# be processing and reporting on.  It will first display the

# standard environment variables and then it takes STDIN and

# dump it right back out to STDOUT.  

# These are the standard environment variables.  You can define

# more in your service config file (see above).

echo "Date Range: $LOGWATCH_DATE_RANGE"

echo "Detail Level: $LOGWATCH_DETAIL_LEVEL"

echo "Temp Dir: $LOGWATCH_TEMP_DIR"

echo "Debug Level: $LOGWATCH_DEBUG"

# Now take STDIN and dump it to STDOUT

cat

###################### Cut Here #########################

If you temorarily replace a script such as 'pam' with the above, you will

notice that much has been cut out of /var/log/messages before it gets to

this filter.  

The value of the environment variable LOGWATCH_DETAIL_LEVEL can be any

integer.  In reality, it is usually 0 (for low), 5 (for medium), and 10

(for high). 

Your script should only produce output as appropriate.  If there are no

relevant log entries, no output should be produced.  Likewise, if you are

reporting two things, such as "Good Logins" and "Bad Logins", you should

only produce even the headers when appropriate.  For example:

Bad Logins:

   amber (2 time(s))

   kirk (3 time(s))

Good Logins:

   amber (5 time(s))

   kirk (10 time(s))

But, if no failed logins occur, you should only output:

Good Logins:

   amber (5 time(s))

   kirk (10 time(s))

Note that there is no "Bad Logins:" header as there were no bad logins.  You

should also use the detail environment variable when deciding what to

output.  Bad logins might always be displayed, but good logins might only be

displayed at higher detail levels.  Here is a guide on how you should

use the detail setting:

0 (Low): Display only errors and security-related issues

5 (Med): Display anything that a typical administator would be interested in

10 (High): Display anything that a paranoid administrator would want to see

In some cases, you can use a security setting higher than 10.  This would be

reserved for information so trivial that it would not even interest the US 

Government.