Nagios fails on empty config file

[Andreas Ericsson]

Ethan Galstad wrote:
> Marc Haber wrote:
>> Hi,
>>
>> this is a forward from the Debian BTS, http://bugs.debian.org/354007.
>>
>> If Nagios 2 encounters an empty config file, it exits with "invalid
>> argument":
>>
>> |Reading configuration data...
>> |
>> |Error: Cannot open config file '/etc/nagios-plugins/config/imap.cfg' for
>> |reading: Invalid argument
>> |
>> |***> One or more problems was encountered while processing the config files...
>> |
>> |      Check your configuration file(s) to ensure that they contain valid
>> |      directives and data defintions.  If you are upgrading from a previous
>> |      version of Nagios, you should be aware that some variables/definitions
>> |      may have been removed or modified in this version.  Make sure to read
>> |      the HTML documentation regarding the config files, as well as the
>> |      'Whats New' section to find out what has changed.
>> |
>> |* errors in config!
>> |  failed!
>> |invoke-rc.d: initscript nagios2, action "start" failed.
>> |root at debian:/etc/nagios-plugins/config#
>>
>> This has been verified to be still present in nagios 2.5.
>>
>> Greetings
>> Marc
>>
> 
> I believe this is proper behavior.  The "Invalid argument" string is 
> coming from the system via the strerror() function.
> 

I'm not sure what filesystem this happens on, but all filesystems I've 
ever worked with allows opening a zero-length file for reading.

Unless the code goes something like this, strerror() should never spit 
out that error string

----
int fd;

fd = open(config_file, O_RDONLY)
fstat(config_file, &st);
if (st.st_size == 0)
	close(fd);

read(fd, buf, size);
----

in which case the "invalid argument" comes from the read() call, and not 
the open() call (I can't imagine the options being wrong for the open() 
call, but I haven't checked it).

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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